86246 SP1B Report TEXT KH - gov.uk · This report is a reference document, describing physical,...

Radionuclides handbook

R&D Technical Report P3-101/SP1b

www.environment-agency.gov.uk


The Environment Agency is the leading public body protecting and

improving the environment in England and Wales.

It’s our job to make sure that air, land and water are looked after by

everyone in today’s society, so that tomorrow’s generations inherit a

cleaner, healthier world.

Our work includes tackling flooding and pollution incidents, reducing

industry’s impacts on the environment, cleaning up rivers, coastal

waters and contaminated land, and improving wildlife habitats.

Published by:

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ISBN : 1844321762© Environment Agency October 2003

All rights reserved. This document may be reproduced with

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Water used is treated and in most cases returned to source in

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Further copies of this report are available from: Environment Agency, Government Buildings,

Burghill Road, Westbury-on-Trym, Bristol BS10 6BF

Tel: 0117 914 2656 Fax: 0117 914 2673

Authors:M Kelly, M Thorne*

Dissemination status:Internal: Released to Regions

External: Public Domain

Statement of use:This report is a reference document, describing physical, chemi-

cal and biological behaviour of radionuclides in the environment.

It was produced to complement R&D project P3-101/1a, aimed

at assessing possible impact of ionising radiation from authorised

discharges on Natura 2000 sites.

Research contractor:Serco Assurance

424 Harwell, Didcot, Oxfordshire, OX11 0QJ

Tel: +44 (0)1235 433005 Fax: +44 (0)1235 436579

* In conjunction with Mike Thorne and Associates Limited

Environment Agency Project Manager:Irene Zinger

Environment Agency Radionuclides Handbook 1

The completion of Stage 2 of the Environment Agency’s Review of Consents process (as required under the

Habitats Regulations 1994) has resulted in a number of RSA93 authorisations requiring a detailed (Stage

3) assessment. This requires an understanding of the environmental transfer characteristics, biotic uptake

and radiological impact of a wide range of radionuclides. There is a need to draw together the relevant

information into a single source document as a wide range of Environment Agency and English Nature

staff will be involved in undertaking the Stage 3 assessments. This report addresses that requirement.

The report is split into two parts:

1. An introduction to radioactivity and its properties, along with some of the global characteristics of the

radionuclides considered in the Handbook

2. Detailed information for a number of radionuclides that may require consideration in the Stage 3

assessments.

The aim of Part 1 of the report is to provide a basic introduction to radioactivity and its properties in

order to set in context the more detailed information provided in Part 2. Part 1 briefly covers the

following:

• fundamental facts about atoms and the nature of radioactivity;

• how radiation interacts with matter and the implications for living organisms;

• the radionuclides considered and their inter-relationships;

• the general features described for each radionuclide in Part 2.

Part 2 provides information about 85 radionuclides, including:

• basic properties

• modes of decay

• chemical properties and analogues

• environmental transfer characteristics

• uptake by, and exposure of, biota

• dosimetric issues.

It is not intended to provide an exhaustive set of properties and characteristics in Part 2. Rather, the aim is

to provide a basic understanding for the environmental behaviour and radiological significance of the

radionuclides and their possible impact on non-human species.

A list of references is given at the end of Part 1, together with some suggestions for additional reading. To

help the reader, a substantial glossary is given at the end of the report.

Executive summary

Contents

Executive Summary 1

List of Tables and Figures 3

Introduction 4

Acknowledgements 4

Part 1 - Brief introduction to radioactivity and its properties 5

1. Introduction to atoms and radioactivity 6

2. Effects of radiation on matter and wildlife 12

3. Radionuclides considered 15

4. Radionuclide data detailed in Part 2 18

5. References 26

Part 2 - Information on each radionuclide - listed by symbol 28

Glossary 204

Environment Agency Radionuclides Handbook2


List of Tables and Figures

Table 1: Selection of radionuclides for the Handbook 16

Table 2: Radionuclides analogues, listed by radionuclide symbol 21

Table 3: Behaviour of radionuclides, listed by radionuclide symbol 22

Figure 1: The periodic table (the first 103 elements) 8

Figure 2: The model of a helium atom 6

Figure 3: Radioactive decay of carbon-14 7

Figure 4: Types of beta decay 10

Figure 5: Example of a radioactive decay chain 11

Figure 6: Ionisation of the helium ion 12

Figure 7: Relative range of travel of alpha and beta particles 13

Figure 8: The cell 13

Figure 9: Origins of radionuclides 23

Figure 10: Main decay modes of radionuclides 24

Figure 11: Main uses of radionuclides 25

Figure 13: Decay mode graphs for strontium-90 19

Introduction

The wide range of staff involved in Stage 3 assessments will need to access basic information on theproperties of radionuclides to help them understand their impact in the environment. While this informationis available from a variety of sources, no single document details the properties and behaviour of the fullrange of relevant radionuclides in the environment. The aim of this Handbook is to address this and to bringbasic information regarding a number of important radionuclides together in a single reference.

The report is divided into two parts.

• Part 1 provides a basic introduction to radioactivity and its properties in order to set in context the moredetailed information provided in Part 2.

• The properties of 85 radionuclides that may be relevant to the radiation protection of wildlife arepresented in Part 2. The intention is not to provide an exhaustive set of properties and characteristics.Rather, the aim is to provide a basic understanding of the environmental behaviour and radiologicalsignificance of a number of radionuclides, and their possible impact on non-human species.

The glossary also includes entries from the glossary given in Environment Agency R&D Publication 128(Copplestone et al., 2001).


The completion of Stage 2 of the Environment Agency’s Review of

Consents process (as required under the Habitats Regulations

1994) has resulted in a number of Radioactive Substances Act

1993 (RSA93) authorisations requiring a full Appropriate

Assessment (Stage 3).

The report draws on work carried out by AEA Technology plc on the production of datasheets for a number ofradionuclides for the Environment Agency’s pollution inventory.

The report was also peer-reviewed by dedicated Agency staff and externally by staff at the University ofLiverpool to ensure that the technical content was accurate and reflected people’s experiences in this field.

Acknowledgements

PART 1Brief introduction to radioactivity and its properties

Fundamental concepts on atoms and the nature of radioactivity are

summarised in Section 1. Section 2 goes on to consider how

radiation interacts with matter and the possible implications for

living organisms, while Section 3 considers some of the general

features of the radionuclides covered in Part 2 of the report.

Section 4 describes the type of information given in Part 2 and

introduces its format. Section 5 lists the references cited in the

report and provides some suggestions for additional reading and a

short list of useful websites.


Further information relating to radioactivity and its properties can be obtained from NRPB (1998).


1. Introduction to atoms andradioactivity

An atom consists of a nucleus, around which rotatesa number of electrons (Figure 2). The radius of theorbits of these electrons is about the same as theatomic size, i.e. 10-8 cm. The radius of the nucleus isabout 100,000 times smaller. Electrons carry anegative electrical charge, whereas the nucleuscarries a positive electrical charge.

The nucleus itself is composed of two types of smallerparticle, called protons and neutrons. These particleshave similar masses (the neutron is slightly heavier),but they differ in that the proton carries a positiveelectrical charge (equal in magnitude but opposite tothe electron). Protons and neutrons differ in otherways, but these are not relevant to this discussion.

Proton

Neutron

Electron

In a simplified model of the atom, electrons rotate around

a nucleus consisting of protons and neutrons. The

diagram above shows a helium atom.

All matter is made up from atoms; an atom is the smallest particle

that has the physical characteristics of any given element. Atoms

are very small - the diameter of the smallest atoms is about 10-8

cm. About 114 different species of atom have so far been

discovered. Each species of atom defines an element such as

oxygen, helium and carbon. Figure 1 shows the first 103 elements

in the form of the periodic table.

The 114 or so elements are identified in terms of thenumber of protons in the nucleus. Elements with lowatomic number are often referred to as light elementsand those with high atomic number are referred to asheavy elements. The lightest element (hydrogen) hasonly a single proton, whereas the heaviest has 114protons. Hydrogen has only a single electron rotatingaround its nucleus, whereas the heaviest has 114electrons. Each element has:

• an atomic number, Z, i.e. the number of protonsin the nucleus;

• a neutron number, N, i.e. the number of neutronsin the nucleus;

• an atomic mass, A, which is the total number ofprotons plus neutrons.

The vertical columns of the periodic table are referredto as ‘groups’; the elements within a group tend tohave similar chemical properties. Thus, for example,sodium (Z = 11) and potassium (Z = 19) both belongto Group 1 and have similar chemical properties.The environmental characteristics of an element forwhich data are scarce can often be inferred byconsidering the properties of other better-understoodelements in the same group. For further information,see Hill and Holman (2000).

Figure 2: Model of a helium atom

1

Radioactivity may be defined as a spontaneousnuclear transformation that usually results in theformation of a different nucleus and occurs when thenucleus is moving to a more stable situation byemitting energy or particles. The transformation fromone nucleus to another nucleus is called radioactivedecay (see the example in Figure 3). Consider anucleus with Z protons and N (equals A - Z)neutrons. The nucleus can only be stable for certaincombinations of Z and N. By ‘stable’, we mean thatthe nucleus remains in the same form (with the sameZ and N) for an infinite period of time. N is generallygreater than Z, but nuclei with more protons thatneutrons can occur, e.g. helium-3 has two protonsand one neutron.

Figure 3: Radioactive decay of carbon-14

The antineutrino (as illustrated in the decay ofcarbon-14 in Figure 3) has a negligible mass andcarries no charge, and consequently is of littlerelevance from the perspective of radiationprotection. It is not considered further in this report.

As another example, stable cobalt has an atom with27 protons and 32 neutrons (Z = 27, A = 59), andmay be written as cobalt-59, or, more technically, as 59Co. However, if the nucleus gains an extraneutron compared with stable cobalt-59, then a newnucleus with Z = 27, A = 60 is formed that isunstable. This is known as cobalt-60 (abbreviated asCo-60), which is said to be radioactive.

The cobalt-60 nucleus is not stable and can onlyexist in that form for a limited amount of time. Thenucleus eventually changes its form to aconfiguration that is stable; this involves a change inthe numbers of protons and neutrons present. Inthis case, one of the neutrons becomes a proton andan electron is emitted from the nucleus. Asexplained later, this electron is called a beta particle.Atoms with nuclei that have the same number ofprotons but differing number of neutrons are calledisotopes. These atoms thus belong to the sameelement and isotopes of an element have essentially

the same chemical properties.

Half-lifeIt is not possible to predict the exact amount of timethat will elapse before any particular unstable nucleusdecays. However, if a large number of such nucleiare present, one can define an average decay time.This is related to an important quantity known as theradioactive half-life. This is defined as the timerequired for half of the nuclei present to decay. Inthe case of cobalt-60, the radioactive half-life isabout 5 years; that is, after about 5 years, we canexpect approximately 500 cobalt-60 atoms to be leftfrom 1,000 cobalt-60 atoms.

The existence and decay of atoms with unstablenuclei is the basis for the existence of radiation andradioactivity. In the example of cobalt-60, theradioactive transformation of the nucleus to a morestable form is accompanied by the emission of anelectron, as one the neutrons in the nucleustransforms itself into a proton. In the case of cobalt-60, this transformation is also accompanied by theemission of a photon of electromagnetic radiation(called a gamma ray). It is the ultimate fate of thesegamma rays and the emitted electron that is ofconcern when considering the radioactive problemsposed by cobalt-60 (cobalt-60 sources are often usedin medical applications of radioactivity). This isdiscussed further in Section 2.

Radionuclide half-lives can vary from very small (forexample, polonium-214 has a half-life of 0.00016seconds) to very large (for example, thorium-232 hasa half-life of 1.4 x 1010 years). In many cases, short-lived radionuclides are only of limited importancewhen released into the environment. This is becausethey will decay before they can be transportedthrough the environment to locations where biotaare exposed to them.


+ + Antineutrino

This neutron has been converted

to a proton

The decay of carbon-14. This isotope has an excess of neutrons

and hence is unstable. It decays by converting a neutron into a

proton, with the emission of an electron and an antineutrino.


HH

yd

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n

1 –

1.0

08

Li

Lith

ium

3 –

6.9

41

Na

So

diu

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11

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KP

ota

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19

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9.1

Rb

Ru

bid

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37

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Cs

Ca

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55

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Fr

Fra

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87

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Be

Be

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Mg

Ma

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Ca

Ca

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20

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Sr

Stro

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38

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Ba

Ba

rium

56

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Ra

Ra

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88

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Sc

Sca

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Lu

Lu

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Lr

La

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Iron

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Me

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Ce

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Sa

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Eu

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63

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Gd

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Tb

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Cf

Ca

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Ho

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Er

Erb

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68

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Fm

Ferm

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Tm

Th

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69

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68

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Md

Me

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10

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Yb

Ytte

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No

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He

He

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Lanth

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Actin

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Gro

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1A

2IIA

2A

3

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3B

4

IVB

4B

5

VB

5B

6

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6B

7

VIIB

7B

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VIII

9

VIII

10

VIII

11

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2B

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15

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5A

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VIIA

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Alk

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Alk

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No

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Actin

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Figure 1: The p

eriodic tab

le (the first 103 elements)

Modes of decayThe most common modes of radioactive decay are:

• alpha decay• beta decay• gamma emission as isomeric transformation (IT)• X-ray emission, e.g. electron capture (EC)• neutron.

Each of these modes of decay is explained below.

Alpha decay (α)Alpha decay is a type of radioactive decay in whichthe nucleus emits an alpha particle - a particle thatconsists of two protons and two neutrons boundtogether. An alpha particle is in fact a heliumnucleus. The alpha particle is emitted with anenergy that is characteristic of the nucleusundergoing the decay.

Plutonium-239 is an example of a radionuclide thatundergoes alpha decay. The alpha decay ofplutonium-239 can be written as follows:

239 235 4

94 Plutonimum → 92 Uranium + 2 Helium

With a few exceptions, alpha decay is only observedin nuclei with more than 82 protons.

Alpha decay is of greatest radiological importance forinternally incorporated radionuclides.

Beta decay (β)• Beta decay is the emission of electrons. They are

most commonly negatively charged (written asβ-), but are sometime positively charged, whenthey are called positrons (written as β+). In thistype of decay either a neutron is converted to aproton and the nucleus emits an electron, forexample:

131 131

53 Iodine → 54 Xenon + β- or

• a proton is converted into a neutron and thenucleus emits a positron (a positively chargedelectron), for example:

22 22

11 Sodium → 10 Neon + β+

The positron produced in the decay of sodium-22interacts with an electron and both ‘destroy’, givingrise to two gamma rays (each of energy 0.511 MeV).

In contrast to alpha decay, the energy of the emittedbeta particle can assume any value from zero up to amaximum value. Calculations of beta doses forradiation protection generally use the average energyof emission, which is about a third of the maximumvalue. Beta decay is often accompanied by theemission of one or more gamma rays.

Beta decay is of radiological importance for internallyincorporated radionuclides and external irradiation.

Gamma decay (γ)Gamma rays are pulses of electromagnetic radiation(called photons) that are emitted when the nucleusundergoes an internal rearrangement of itsconstituent protons and neutrons. The energy of thegamma ray is equal to the energy difference betweenthe initial and final (lower) energy states of thenucleus, and the emission is required to conserveenergy. Radiowaves, microwaves and visible light aremore familiar examples of electromagnetic radiation.

Usually, a gamma ray is emitted following beta decay(and occasionally alpha decay). Once the decay hasoccurred, the resultant nucleus is left in one of itshigher energy states. It moves back down to itslowest energy state by emitting one or more gammarays.

As illustrated in Figure 4, two types of beta decay areoften considered in radiation protection, as not allbeta emitters emit a gamma ray:

• pure beta emitters emit beta particle only, e.g.hydrogen-3;

• beta-gamma emitters emit beta particles andgamma rays, e.g. cobalt-60.



Figure 4: Types of beta decay

In many cases, the gamma rays are of greaterradiological significance. Thus, cobalt-60 decays bybeta decay, but the gamma rays are the mostimportant when assessing the radiologicalconsequences of cobalt-60.

Another important class of radionuclides is those thatbeta decay to a metastable radionuclide (see belowunder isomeric transformation), which in turn emits agamma ray when it decays. An example is caesium-137, which beta decays to barium-137m (an excitedstate of barium-137), which in turn emits a gammaray as it decays to stable barium-137. In 89 % ofsubsequent decays of barium-137m, excess energy islost by emitting a gamma ray and, in the remaining11 % of cases, by internal conversion (see belowunder X-ray emission). Once again, it is the gammaray emitted by barium-137m that is of greatersignificance than the beta particle emitted bycaesium-137.

Gamma rays can be emitted without any previousalpha or beta decays by certain metastable speciessuch as Tc-99m and In-113m. These emit gammarays when they decay from their excited states to theground state via an isomeric transformation of thenucleus.

Gamma decay is of greatest radiological importancein the context of external irradiation. For largerspecies, however, internally incorporated gammaemitters are also important.

Isomeric transformation (IT)The release of gamma radiation from alpha or betadecay is sometimes delayed and the daughternucleus survives in a higher energy state (themetastable state) for some time before it returns to alower energy state by emitting gamma rays. Thisform of decay is called an isomeric transformationand the metastable state is denoted by the letter ‘m’

after the atomic mass, for example, technetium-99m.Technetium-99m decays to technetium-99 via anisomeric transformation, emitting a gamma ray as itdoes so.

X-ray emissionX-ray emission arises during a type of radioactivedecay known as internal conversion. Instead ofshedding its excess energy by emitting a gamma ray,an excited nucleus can dispose of its excess energyby interacting with one of the inner electronsorbiting the nucleus. This electron in turn absorbsthe excess energy and is ejected from the atom.When internal conversion occurs, other orbitingelectrons can ‘fall’ into the orbit vacated by theejected electron. When this happens, the electronloses energy, and an X-ray is emitted.

Orbital electron capture (EC) is another process thatproduces X-rays. Here, the nucleus captures one ofthe electrons orbiting the nucleus. As above, X-raysare emitted as the orbiting electrons rearrangethemselves to fill the orbit vacated. The electroninteracts with one of the protons to produce aneutron and a neutrino is ejected from the nucleus.The neutrino, however, has no radiologicalsignificance. Sodium-22 can decay by orbitalelectron capture, as well as by positron emission.

An outer electron falls into the vacancy left by thecaptured electron and an X-ray is emitted.

NeutronsNeutrons are usually produced in a laboratory ornuclear reactor when a nuclear transformation isinduced, for example, by taking an atom and firinganother nuclear particle at it, or when radioactivefission occurs. Fission is the breaking up of a largeunstable nucleus into two roughly equal nuclei, eacharound half the size of the original; this processliberates considerable amounts of energy. Theeffects of neutrons will not be considered further inthe context of environmental radioactivity.

The modes of radioactive decay discussed above leadto the production of new nuclides from the original.In some cases, the new nuclide will be stable.However, successive decays can lead to newradioactive species. In such cases, radioactive decaychains are formed. Figure 5 shows the decay chainfor uranium-238.

Nuclear

energy

levels

Nuclear

energy

levels

(lowest) (lowest) Emitted

gamma

ray

Pure beta decay Beta-gamma decay

++

In pure beta decay, the resultant nucleus is in its ground state.

In beta-gamma decay, the resultant nucleus is in an excited

state, and returns to the ground state by emitting a gamma ray.


Uranium-238

4.468 109 years

Thorium-234

24.1 days

Protactinium-234m

1.17 minutes

Uranium-234

2.45 105 years

Thorium-230

77000 years

Radium-226

1600 years

Radon-222

3.8 days

Polonium-218

3.05 minutes

Lead-214

26.8 minutes

Bismuth-214

19.9 minutes

Polonium-214

1.6 10-5 seconds

Polonium-210

138 days

Bismuth-210

5.01 days

Lead-210

22.3 years

Lead-206

stable

Alpha decay

Beta decay

Beta decay

Alpha decay

Alpha decay

Alpha decay

Alpha decay

Alpha decay

Beta decay

Beta decay

Alpha decay

Beta decay

Beta decay

Alpha decay

Figure 5: Example of a radioactive decay chain (decay data from ICRP Publication 38)


To appreciate why these types of radiation arepotentially damaging to living entities, it is necessaryto understand how they interact with matter and, inparticular, living tissue and cells. It should be bornein mind that, just like all other matter, living tissueconsists of a collection of atoms and moleculesbound together to form the tissue mass. As before,further information relating to the effects of radiationon matter can be obtained from NRPB (1998).

Alpha and beta particlesAlpha and beta particles (and other chargedparticles) are often referred to as directly ionisingradiation. This is because, when an alpha or betaparticle enters living tissue, it interacts directly withthe outer electrons of the constituent atoms and, if itsupplies enough energy, it can knock the outerelectrons away from the atoms. The end products ofsuch an event are a free electron and a positivelycharged ion. This process is called ionisation (seeFigure 6) and is the basic physical mechanism thatgives rise to radiological detriment and harm.

Because alpha and beta particles have substantiallydifferent masses and different charges, the rates atwhich the two types of particle cause ionisation arevery different:

• beta particle produces >100 ionisation events percm of travel;

• alpha particle produces >10,000 ionisation eventsper cm of travel.

Alpha particles therefore cause considerably moreionisations (and hence radiological damage).However, as shown in Figure 7, this is partly offset bythe fact that alpha particles have a very much smallerrange of travel in body tissue than beta particles ofthe same energy (of the order of micrometrescompared with centimetres for beta particles). Asthe energy of either particle increases, so the rangeincreases.

Figure 6: Example of the ionisation of an atom

The previous section described how radioactive decay can lead to

the following by-products:

• alpha particles (helium nuclei)

• beta particles (electrons or positrons)

• gamma rays (high energy electromagnetic radiation)

• X-rays.

2. Effects of radiation on matter andwildlife

Ionisation of the helium atom. The helium ion on the

right has lost an electron, compared with the neutral

helium atom on the left.

2

Figure 7: Relative range of travel of alpha and betaparticles

A consequence of this is that alpha-emittingradioisotopes rarely pose a radiological hazard outsidethe body, as the alpha particles are not able topenetrate through skin. When alpha particles aretaken into the body, for example by inhalation intothe lung, the radiological hazard is high due to thevery high rate of ionisation as they slow down in lungtissue.

Gamma raysIn contrast to alpha and beta particles, gamma raysinduce ionisation in the atoms of living tissue byindirect means (the result of indirect ionisingradiation). There are three principal mechanisms bywhich gamma rays interact with living tissue:

• Compton scattering• photoelectric effect• pair production.

In the Compton effect, the gamma rays are scatteredfrom the outer electrons of the atoms, transferringenergy to the electrons and in the process reducingthe energy of the gamma ray. If enough energy issupplied during scattering, the outer electron will beremoved from the atom, leaving an ion and giving riseto a free electron.

The photoelectric effect and pair productionmechanisms are important for low and high gammaenergies, respectively. For the gamma rays emitted bythe majority of radionuclides, this can pose anenvironmental hazard. Compton scattering is the mostimportant interaction mechanism.

Microscopic effects of radiationTo understand the nature of the damage caused byradiation, it is necessary to look at the microscopicstructure of living organisms. Any living animal orplant is composed of a large number of individual cells(see Figure 8). These cells can be split broadly intotwo categories, namely somaticm cells and germ cells.

Germ cells are responsible for the reproduction ofoffspring and constitute the sperm in males and theova in females. All other cells fall under theclassification of somatic cells.

Figure 8: The cell

The genetic information that characterises anyindividual is contained within the chromosomes. Indogs, for example, the somatic cells contain 78chromosomes (39 chromosomes occurring in pairs)and germ cells contain 39 chromosomes (39chromosomes occurring once), so that when a spermand an ovum come together they produce acomposite with the full 78 chromosomes. All cells inthe body contain exactly the same geneticinformation; when cells divide, the chromosomes arereproduced exactly so that the new cells resultingfrom cellular division contain exactly the samegenetic information as in the original cell.

Suppose that a collection of cells in a living organismis subject to the types of radiation described above.The main effect of this radiation is to cause ionisationof the atoms in the absorbing medium. Thus, whencells are irradiated, it is likely that ionisation of one ormore of the atoms on some of the DNA moleculeswill occur. This can lead to a number ofconsequences for the affected molecule. Theseeffects include:

• breakage of the chains of molecules comprisingthe DNA;

• breakage of the links between chains.

In many cases, the cell is able to repair the damage,but not always. For example, single-strand breakswithin DNA can often be repaired without error,whereas double-strand breaks cannot. When thedamage cannot be repaired, the affected cell is left


Beta

Alpha particles and beta particles show different behaviour when interacting

with matter. Alphas, on account of their mass, tend to follow straight paths,

whereas the much lighter beta particles tend to follow more random paths.

Beta particles can travel

up to 0.1 m

Alpha

Beta

Alpha particles only travel

around 0.000001 m

Beta particles can travel

up to 0.1 m

The chromosomes are composed largely of

DNA, and consist of linear sequences of genes

The cell nucleus, which

contains, among other

things, the chromosomes

The nucleolus, whose

primary role is ribosome

manufacture

Ribosomes, which are particles made up from

RNA and protein molecules, and which are the

sites for protein synthesis. Proteins are

fundamental to the structure of all organisms.

The cytoplasm. Contains the other living

contents of the cell, and provides the pathway

through which they communicate with each

other.

The cell. The above is a very simplified picture of a typical cell in animals and

humans. The characteristics (e.g. hair colour, blood group) of an individual is

determined by thecomposition of the genes, from which the chromosomes are

composed. DNA forms a “chemical” template for protein synthesis, which in

The cytoplasm. Contains the other living

contents of the cell, and provides the pathway

through which they communicate with each

other.

The cell. The above is a very simplified picture of a typical cell in animals and

humans. The characteristics (e.g. hair colour, blood group) of an individual is

determined by thecomposition of the genes, from which the chromosomes are

composed. DNA forms a “chemical” template for protein synthesis, which in

The nucleolus, whose

primary role is ribosome

manufacture

The cell nucleus, which

contains, among other

things, the chromosomes

Ribosomes, which are particles made up from

RNA and protein molecules, and which are the

sites for protein synthesis. Proteins are

fundamental to the structure of all organisms.

The chromosomes are composed largely of

DNA, and consist of linear sequences of genes

turn is mediated by RNA.


with altered or damaged genetic informationcompared with the unaffected cells. All descendantsof that cell will also contain altered or damagedinformation because cellular division results in exactreplication of the genetic information in the originalcell.

The multiplication of damaged cells in this way is thebasis for the induction of cancer in mammals.However, in the context of wildlife populations, anumber of alternative endpoints have been identifiedthat can be studied after exposure to radiation.These include:

• morbidity, e.g. illness and lifetime shortening;• mortality;• changes in reproductive capacity (including

fertility and fecundity);• mutation.

UNSCEAR (1996) provides a useful review of studiesrelating to the effects of ionising radiation on non-human species. UNSCEAR (1996) concluded that,overall, the general capacity of plant communities towithstand general stresses and changes within theenvironment also enables them to withstand low tomoderate radiation stress. There may be alterationsto community structure and morphological changesto individual plants (depending on the level ofradiation exposure), but the compensations aregenerally such as to maintain a normal energybalance.

Changes in animal communities in terrestrialenvironments seem mainly to arise indirectly as aconsequence of changes to the plant community.When plant species die in highly irradiated areas, thefood supplies of herbivorous animals and theirpredators are reduced. These animals may disappearand be replaced by species that depend on dead anddecaying material. Some of these species mayfurther damage remaining vegetation, which mightotherwise have survived.

Because of the compensation and adjustmentpossible in animal species, UNSCEAR (1996)considered it unlikely that radiation exposurescausing only minor effects in the most exposedindividual would have significant effects on thepopulation. Similar views are expressed in respect toaquatic communities.

Studies and interpretation of the effects of radiationon non-human species are ongoing. One example isthe EC 5th Framework Programme project, FASSET(Framework for ASSessment of EnvironmentalimpacT). A recent output from this project is areport by Woodhead and Zinger (2003) on radiationeffects to plants and animals.

3. Radionuclides considered

The selection of radionuclides originate from:

• the Environment Agency’s knowledge ofradionuclides present in regulatoryauthorisations;

• those identified by FASSET (Strand et al., 2001);• those used in assessment spreadsheets contained

in Agency guidance on implementing theHabitats Regulations 1994 (Allott and Dunn,2001).

Table 1 lists the chosen radionuclides detailed in Part 2. For a few elements, some radionuclides areproduced under two forms, for example, Tc-99 andTc-99m. The ‘m’ stands for ‘metastable’ (see Section 2). The Tc-99m nucleus has the samestructure as the Tc-99 nucleus, but exists in a higherenergy state and can remain there for a reasonablylong period of time. It decays to Tc-99 by emitting agamma ray.

More detailed information for these radionuclides isprovided in Part 2 in the form of two-pagesummaries of their key properties and characteristics,catalogued by radionuclide symbol, for example, Au-98 and Cs-137 (and not element name). Thepurpose of the Handbook is not to provide anexhaustive set of properties and characteristics for allradionuclides. The aim is rather to provide an insightinto the environmental behaviour and radiologicalsignificance of the radionuclides for non-humanspecies.

The use of numerical parameters has been avoidedwhere possible, although in some cases order-of-magnitude estimates of transfer parameters havebeen given to provide an indication of radionuclidesand species that are assimilated with particularefficiency into biological systems.

At the beginning of Part 2, radionuclides are listed bytheir symbols (e.g. Cs-137) and an index is givenwhich points to their location in the Handbook.

For this study, 85 radionuclides of possible environmental

significance to wildlife have been considered. Many of these

radionuclides originate from medical or industrial applications, or

are by-products of nuclear power generation. Total alpha emitters,

total beta emitters and depleted uranium are also considered.


3


Element Radionuclide Symbol Origin of selectionAmericium Americium-241 Am-241 FASSET, Pub128Antimony Antimony-125 Sb-125 AgencyArgon Argon-41 Ar-41 Pub128Bromine Bromine-82 Br-82 AgencyCaesium Caesium-134 Cs-134 FASSET

Caesium-135 Cs-135 FASSETCaesium-137 Cs-137 FASSET, Pub128

Calcium Calcium-45 Ca-45 AgencyCalcium-47 Ca-47 Agency

Carbon Carbon-11 C-11 AgencyCarbon-14 C-14 FASSET, Pub128

Cerium Cerium-144 Ce-144 AgencyChlorine Chlorine-36 Cl-36 FASSET, AgencyChromium Chromium-51 Cr-51 AgencyCobalt Cobalt-57 Co-57 Agency

Cobalt-58 Co-58 AgencyCobalt-60 Co-60 Pub128

Curium Curium-242 Cm-242 FASSETCurium-243 Cm-243 FASSETCurium-244 Cm-244 FASSET

Erbium Erbium-169 Er-169 AgencyFluorine Fluorine-18 F-18 AgencyGallium Gallium-67 Ga-67 AgencyGold Gold-198 Au-198 AgencyIndium Indium-111 In-111 Agency

Indium-113m In-113m AgencyIodine Iodine-123 I-123 Agency

Iodine-125 I-125 Pub128Iodine-129 I-129 FASSET, Pub128Iodine-131 I-131 FASSET, Pub128

Iron Iron-59 Fe-59 AgencyKrypton Krypton-79 Kr-79 Agency

Krypton-81 Kr-81 AgencyKrypton-85 Kr-85 Pub128

Lanthanum Lanthanum-140 La-140 AgencyLead Lead-210 Pb-210 FASSETManganese Manganese-54 Mn-54 Agency

Manganese-56 Mn-56 AgencyMolybdenum Molybdenum-99 Mo-99 AgencyNeptunium Neptunium-237 Np-237 FASSETNickel Nickel-59 Ni-59 FASSET

Nickel-63 Ni-63 FASSETNiobium Niobium-94 Nb-94 FASSET

Niobium-95 Nb-95 Agency

Agency = Environment AgencyPub128 = R&D Publication 128N/A = not applicable

FASSET = Framework for ASSessment ofEnvironmental ImpacT (EC 5th Framework project)

Table 1 Selection of radionuclides for the Handbook


Element Radionuclide Symbol Origin of selectionOxygen Oxygen-15 O-15 AgencyPhosphorus Phosphorus-32 P-32 Pub128

Phosphorus-33 P-33 AgencyPlutonium Plutonium-238 Pu-238 FASSET

Plutonium-239 Pu-239 FASSET, Pub128Plutonium-240 Pu-240 FASSETPlutonium-241 Pu-241 FASSET

Polonium Polonium-210 Po-210 FASSET, Pub128Potassium Potassium-40 K-40 FASSETPromethium Promethium-147 Pm-147 AgencyProtactinium Protactinium-234m Pa-234m AgencyRadium Radium-226 Ra-226 FASSET, Pub128Radon Radon-222 Rn-222 AgencyRhenium Rhenium-186 Re-186 AgencyRubidium Rubidium-81 Rb-81 Agency

Rubidium-86 Rb-86 AgencyRuthenium Ruthenium-106 Ru-106 FASSET, Pub128Samarium Samarium-153 Sm-153 AgencySelenium Selenium-75 Se-75 AgencySodium Sodium-22 Na-22 Agency

Sodium-24 Na-24 AgencyStrontium Strontium-89 Sr-89 FASSET, Pub128

Strontium-90 Sr-90 FASSET, Pub128Sulphur Sulphur-35 S-35 Pub128Technetium Technetium-99 Tc-99 FASSET, Pub128

Technetium-99m Tc-99m AgencyThallium Thallium-201 Tl-201 AgencyThorium Thorium-227 Th-227 FASSET

Thorium-228 Th-228 FASSETThorium-230 Th-230 FASSETThorium-231 Th-231 FASSETThorium-232 Th-232 FASSETThorium-234 Th-234 Pub128

Total alphas N/A N/A AgencyTotal Betas N/A N/A AgencyTritium Tritium H-3 FASSET, Pub128Uranium Uranium-234 U-234 FASSET

Uranium-235 U-235 FASSETUranium-238 U-238 FASSET, Pub128Depleted uranium N/A Agency

Vanadium Vanadium-48 V-48 AgencyXenon Xenon-133 Xe-133 AgencyYttrium Yttrium-90 Y-90 AgencyZirconium Zirconium-95 Zr-95 Agency

Agency = Environment AgencyPub128 = R&D Publication 128N/A = not applicable

FASSET = Framework for ASSessment ofEnvironmental ImpacT (EC 5th Framework project)

Table 1 continued


4. Radionuclide data detailed in Part 2

Basic information is supplied on the physical, chemical,

environmental and dosimetric behaviour of some 85 radionuclide.

The Handbook is set out in alphabetical order of thesymbol for each radionuclide (e.g. Ga-67 and In-111)rather than the name of the element. Table 1 can beused to identify the correct radionuclides, based ontheir element.

For ease of reference, the page layout for eachradionuclide is identical. Each part of the template isexplained below.

NameThe name of the element of which the radionuclideis an isotope and its mass number.

SymbolThe usual symbol for the radionuclide

OriginA classification to indicate how the radionuclide isproduced or arises. Where more than one of theseapplies to a radionuclide, the principal mode oforigin is listed. There are six possible choices (seeFigure 9 and Part 2).

• Activation. The process in which non-radioactiveelements are converted to radioactive elementsas a result of exposure to radiation in a nuclearreactor or weapon explosion. An example is theformation of techetium-99m for medicalpurposes from the irradiation of molydenum-99.

• Breeding. The production of one radionuclidefrom another due to the action of incidentatomic particles. An example is the productionof plutonium-239 from uranium-238.

• Cosmogenic. These are radionuclides producedin the upper atmosphere due to the action ofcosmic rays.

• Fission. A nuclear reaction in which an atom oflarge atomic mass splits into two atoms ofsmaller mass, with the production of one ormore neutrons and the release of energy.

• Primordial. These are radionuclides left overfrom the creation of the universe. Theynecessarily have very long half-lives, for example,uranium-238 and thorium-232.

• Radiogenic. A term applied to radionuclides thatarise from the decay of other radionuclides.

Radioactive half-lifeThe half-life of the radionuclide

Principle decay modeThe principal mode of radioactive decay for theradionuclide as described in Section 2. Figure 10shows the allocation of the investigated radionuclidesinto the four groups referred to in Part 2. The fourgroups are as follows.

• Alpha. Nuclear particles consisting of fast-moving helium nuclei (atomic mass of 4 andatomic number 2).

• Beta. A negatively charged (electron) orpositively charged (positron) particle emittedfrom the nucleus of an atom during radioactivedecay.

• X-ray as orbital electron capture (EC). A form ofradioactive decay in which the nucleus capturesan orbiting electron, converting a proton to a

Name

Symbol

Origin

Radioactive half-life

Principal decay mode

Grouping

4

neutron. The energy is released as gamma or X-rays.

• Gamma as isomeric transformation (IT). Verypenetrating electromagnetic radiation frequentlyemitted from the nucleus of an atom duringradioactive decay. IT is a form of radioactivedecay in which a metastable nucleus decays withthe release of energy as gamma rays.

For some radionuclides, the principal decay mode isnot the one of greatest significance from a radiationprotection perspective. For example, in the decay ofcobalt-60, the gamma rays emitted are of greaterimportance than the beta particle. Where this is thecase, the most radiologically significant emissions aregiven in square brackets.

GroupingAn indication of whether the radionuclide arisesnaturally in the environment or by artificial means(for example, in a nuclear reactor). The options forthis box are ‘natural’ or ‘artificial’.

ParentThe radionuclide(s) whose decay would give rise tothe radionuclide. This entry is set to ‘N/A’ if theparent is not produced naturally or artificially insignificant quantities.

DaughterThe nuclide that arises from decay of theradionuclide; it may be radioactive or stable. Wherethe daughter is itself radioactive, it is followed by acapital R in square brackets, i.e. [R].

DetectionAn indication of whether the radionuclide can bedetected ‘in the field’ or whether laboratory analysisis required. The options are ‘in situ’ and ‘laboratory’.As a general rule, strong gamma emitters can bedetected easily in situ, or even by aerial monitoringwith a fixed-wing aircraft. Radionuclides that onlyhave weak or zero gamma emissions usually have tobe identified from sample analysis in a laboratory(alpha and beta particles have limited ranges in air).

Production, uses and modes of release Figure 11 groups the radionuclides according to theirmain industrial, medical and research applications.

Decay modes (graphs)Information about the modes of decay for eachradionuclide is provided in the form of two graphs.The first provides an indication of the energies of thevarious emissions during decay, along with thefraction of decays that give rise to each emission.The second provides an indication of the nucleartransformations that arise during each decay. Forexample, the two graphs for strontium-90 are shownin Figure 12.

Figure 12: Decay mode graphs for strontium-90

The left-hand graph shows the decay energies anddecay fractions. The right-hand graph is a simplifieddecay scheme, which indicates the nucleartransformation that takes place during the betadecay of strontium-90. Decay data were obtainedfrom ICRP Publication 38.


Parent

Daughter

Detection

Production Uses

Modes Land

of Air

release Water


Chemical properties/characteristics

The chemical properties of most elements can mosteasily be described using the concept of oxidationnumber. The oxidation number is the number ofelectrons that must be added to a positive ion orremoved from a negative ion to produce a neutralatom. Thus, for example, for vanadium in anoxidation state of +5, five electrons must be addedto produce neutral vanadium.

Behaviour in the environment

Exposure routes and pathways

Effects on organisms

Dose effects/dosimetry

A description of thekey radiologicalhazards posed by theradionuclide whentaken up by biota.

Species-specificconsiderations

Specific issues relatingto particular biota - forexample species thatmight acquireparticularly highradiation doses

Speciation

The chemicalproperties of theelement of which theradionuclide is anisotope.

Analogue species

Other elements orradionuclides thatshow similar chemical,environmental orradiological behaviourto the radionuclide.

Table 2 gives anoverview of theproposed substitutes.

Terrestrial Aquatic Atmospheric

A description of the key features of the behaviourof the radionuclide in the terrestrial, aquatic andatmospheric environments

Most radionuclides listed in the Handbook areparticle reactive and will become bound insediments or soil. Table 3 summarises thebehaviour of radionuclides (i.e. particle reactiveversus conservative).

Environmental sink

A description of theultimate fate of theradionuclide in theenvironment

Intake and uptake routes

A description of themost importantradionuclide uptakeroutes for biota

Symbol Analogue(s)Am-241 2nd = Cm NoneAr-41 Ne, Ar, Kr, XeAu-198 NoneBr-82 ClC-11 C-12 C-13 CC-14 C-12 C-13 CCa-45 Ca, Sr, Sr-90Ca-47 Ca, Sr, Sr-90Ce-144 Am,

2nd = Ce, Pr, Nd,Pm, Sm, Eu, Gd, Tb,Dy, Ho, Er, Tm, Yband Lu

Cl-36 Cl ClCm-242 Am NoneCm-243 Am NoneCm-244 Am NoneCo-57 Co for plantsCo-58 Co for plantsCo-60 Co for plants

Cs-137 (a, f)Sr-90 (m)

Cr-51 CrCs-134 K KCs-135 K KCs-137 K KDepleted U-238UraniumEr-169 Am,


F-18 NoneFe-59 FeGa-67 GaH-3 H H Ca-14I-123 II-125 I I-129

Symbol Analogue(s)I-129 II-131 I Cs-137In-111 NoneIn-113m NoneK-40 Cs (2nd) KKr-79 Ne, Ar, Kr, XeKr-81 Ne, Ar, Kr, XeKr-85 Ne, Ar, Kr, XeLa-140 Am,


Mn-54 MnMn-56 MnMo-99 MoNa-22 Na for animalsNa-24 Na for animalsNb-94 Zr NoneNb-95 ZrNi-59 Ni NiNi-63 Ni NiNp-237 Np NoneO-15 OP-32 PO4- Cs-137P-33 PO4- Cs-137Pa-234m NonePb-210 Pb, Ca NonePm-147 Ce, Sm, Eu, PmPo-210 Pb-210 NonePu-238 Pu , 2nd = Np, Am,

Cm NonePu-239 Pu , 2nd = Np, Am,



Cm NoneRa-226 2nd = Ca, Sr, Ba Ca


Symbol Analogue(s)Rb-81 K, CsRb-86 K, CsRe-186 NoneRn-222 NoneRu-106 None Cs-137S-35 S

Cs-137 (f, m)Sb-125 NoneSe-75 Se, SSm-153 Ce, Eu, SmSr-89 Ca CaSr-90 Ca CaTc-99 Tc N (NO3-)Tc-99m Tc Cs-137Th-227 ThTh-228 Th NoneTh-230 Th NoneTh-231 Th NoneTh-232 Th NoneTh-234 ThTl-201 KTotal Nonealpha Ra-226 (a),

U-238 (f, m)Total Nonebeta Cs-137 (a),

Sr-90 (f, m)U-234 U None U-238U-235 U None U-238U-238 U NoneV-48 VXe-133 Ne, Ar, Kr, XeY-90 Ce, Sr-90Zr-95 Nb

FASSET (Strand et al., 2001)Agency ‘Stage 2’(Allott and Dunn, 2001):

a = airf = freshwaterm = marine waters

Table 2 Radionuclide analogues, listed by radionuclide symbol


Symbol C or PAm-241 PAr-41 CAu-198 PBr-82 CC-11 CC-14 CCa-45 PCa-47 PCe-144 PCl-36 CCm-242 PCm-243 PCm-244 PCo-57 PCo-58 PCo-60 PCr-51 C+PCs-134 PCs-135 PCs-137 P+CEr-169 PF-18 -Fe-59 PGa-67 -H-3 CI-123 CI-125 CI-129 CI-131 CIn-111 -In-113m -K-40 CKr-79 CKr-81 CKr-85 CLa-140 PMn-54 PMn-56 PMo-99 C+PNa-22 CNa-24 CNb-94 PNb-95 P

Symbol C or PNi-59 PNi-63 PNp-237 PO-15 -P-32 C+PP-33 C+PPa-234m - as Th (P)Pb-210 PPm-147 PPo-210 PPu-238 PPu-239 PPu-240 PPu-241 PRa-226 -Rb-81 C+PRb-86 C+PRe-186 -Rn-222 -Ru-106 PS-35 C+PSb-125 CSe-75 PSm-153 PSr-89 CSr-90 CTc-99 P+CTc-99m P+CTh-227 PTh-228 PTh-230 PTh-231 PTh-232 PTh-234 PTl-201 CU-234 CU-235 CU-238 CV-48 C+PXe-133 -Y-90 PZr-95 P

P = Particle reactive, i.e. binds to particlesC = Conservative, i.e. remains in solutionP+C = form will depend on environment (freshwater versus marine)- = not stipulated, usually because of its short half-life.

Table 3 Behaviour of radionuclides, listed by radionuclide symbol


Rad

ionu

clid

es S

orte

d by

Orig

in

Ato

mic

Mas

s

Hal

f Life

(yr

)

050

100

150

200

250

Tril

lion

Ten

billi

on

Hun

dred

mill

ion

Mill

ion

1000

0

100

0.01

0.00

01

K40

CI-

36

C-1

4

Ni-5

9

Kr-

81

I-12

9 Cs-

135

TC

-99

Nb-

94

Ni-6

3 Kr-

85H

-3N

a-22

Th-

232

U-2

33

U-2

35

Np-

237

U-2

34T

h-23

0P

u-20

9

Pu-

240

Pu-

241

Pu-

238

Ra-

226

Pb-

210

Cs-

137

Sr-

90 Ru-

106

Pm

-147

P-3

2P

-33

S-3

5

Na-

24

F-1

8

Cr-

51

Ca-

47

Ca-

41M

n-56

Ca-

45 V-4

8

Co-

60S

r-89

Mn-

54

Co-

57

Sc-

75

Co-

58F

e-59

Kr-

79B

r-82C

a-67

Rb-

86

Y-9

0

Rb-

81Tc

-99m

In-1

13m

Mo-

99

Zr-

95N

b-95

I-12

5

n-12

1 La-1

40

I-12

3S

m-1

53

Sb-

125C

s-10

4

Ce-

144

I-13

1K

e-13

3B

r-10

9R

a-18

6

Au-

198

TI-

201

Po-

210

Th-

227

Rn-

222

Th-

223

Cm

-242

Th-

234

Th-

231

1

Am

-241

Cm

-243

Cm

-244

Fig

ure

9: O

rig

ins

of r

adio

nucl

ides

Act

ivat

ion

Bre

edin

gC

osm

ogen

icF

issi

onP

rimor

dial

Rad

ioge

nic


Radionuclides S

orted by Decay M

ode

Atom

ic Mass

Half Life (yr)

050

100150

200250

Trillion

Tenbillion

Hundredm

illion

Million

10000

100

0.01

0.0001

1

K-40

Th-232

U-238

U-235

I-129Cs-135

Kr-81

CI-36

Ni-59

Tc-99

Nb-94

Np-237

U-234

Th-230

Ra-226

Pu-280

Pu-240

Pu-241

Pu-238

Pb-210

Th-228

C-14

Ni-63

Am

-241C

m-243

Cm

-244

Cm

-242

Th-204

Th-231

Sr-90

Cs-137P

m-147

Cs-131

Kr-35

Mn-54

Co-57

H-3

Na-22

Ca-45

S-35

P-32

P-33

Na-24

F-13

Ca-41

Mn-56

Ca-47

Cr-51

V-48

Co-60

Sr-89

Se-75

Ru-106

Zr-95

Nb-95

I-125C

o-58F

e-59R

b-86G

a-67K

r-79B

r-82Y

-90M

o-99

Sb-125

Ce-144

In-111

Rb-81

Tc-99mIn-113m

La-140

I-123S

m-153

I-134X

e-133E

r-160

Po-210

Re-186

Au-198

TI-201

Th-227

Rn-222

Figure 10: M

ain decay m

odes of rad

ionuclides

Alpha

Beta

EC

(X-ray)

IT (G

amm

a Ray)


Rad

iona

cide

s S

orte

d by

Usa

ge

K-4

0

CI-

36

Ni-5

9

Kr-

81Tc

-99

Nb-

94

C-1

4

Ni-6

3M

n-54

H-3

Na-

22C

o-57

Kr-

85

Co-

60

Sr-

90 Ru-

106

Sr-

89C

a-45

S-3

5

P-3

2P

-33

Na-

24

F-1

8C

a-41

Mn-

56

Ca-

47

Cr-

51V-4

8

Se-

75

Co-

58F

e-59

Rb-

86G

a-67

Kr-

79B

r-82

Tc-9

9m

Y-9

0M

o-99

Nb-

95Z

r-95

I-12

5

In-1

11Sb-

125

La-1

40I-

123

In-1

13mC

s-13

4Cs-

137 P

m-1

47

Ce-

144

I-13

1X

e-13

3

Sm

-153

Er-

169

Pb-

210

Po-

210

Ti-2

01A

u-19

8

Re-

186

Th-

227

Rn-

222

Ra-

226

Th-

228

Pu-

241

Cm

-244

Th-

230

U-2

34 Pu-

239

Pu-

240

Np-

237

U-2

35

U-2

38

Th-

232

Cm

-243

Am

-241

Pu-

238

Th-

231

Th-

234

Cm

-242

Rb-

81

I-12

9 Cs-

135

Tril

lion

Hal

f Life

(yr

)

Ten

billi

on

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dred

m

illio

n

Mill

ion

1000

0

100

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010

5010

015

020

025

0

Ato

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Fig

ure

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Mai

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Non

e


Allott, R. and Dunn, M., 2001. Assessment ofradioactive discharge screening levels for biotaprotected under the Habitats Regulations.Environment Agency NCAS Technical Report:NCAS/TR/2001/019. Environment Agency,Lancaster.

Copplestone D., Bielby S., Jones S.R., Patton D.,Daniel P and Gize I., 2001. Impact assessment ofionising radiation on wildlife. Environment AgencyR&D Publication 128. Environment Agency, Bristol.

Hill, G. and Holman, J.S., 2000. Chemistry incontext, 5th edition. Nelson Thornes Cheltenham.

International Atomic Energy Agency (IAEA), 1994.Handbook of parameter values for the prediction ofradionuclide transfer in temperate environments.IAEA Technical Reports Series No. 364. IAEA,Vienna.

International Atomic Energy Agency (IAEA), 2000.Safety glossary - terminology used in nuclear,radiation, radioactive waste and transport safety.IAEA version 1, April 2000. Available fromhttp://www.iaea.org/ns/CoordiNet/index.htm (theCoordinNet page of Nuclear Safety).

International Commission on Radiological Protection(ICRP). Radionuclide transformations: energy andintensity of emissions, ICRP Publication 38. Annalsof the ICRP, 11-13, 1983.

National Radiological Protection Board (NRPB), 1998.Living with radiation, 5th edition. NRPB, Chilton,Oxfordshire.

Strand, P., Beresford, N., Avila, R., Jones, S.R. andLarsson, C.-M. (editors), 2001. FASSET DeliverableD1: Identification of candidate reference organismsfrom a radiation exposure pathways perspective,FASSET Contract FIGE-CT-2000-00102. Availablefrom http://www.fasset.org (go to the Resultspage).

United Nations Scientific Committee on the Effects ofAtomic Radiation (UNSCEAR), 1996. Sources andeffects of ionizing radiation. 1996 Report to theGeneral Assembly, with Annexes. United Nations,New York

United Nations Scientific Committee on the Effects ofAtomic Radiation (UNSCEAR), 2000. Exposures tothe public from man-made sources of radiation.2000 Report to the General Assembly, Annex C.United Nations, New York.

Woodhead D. and Zinger I. (editors), 2003. FASSETDeliverable D4: Radiation effects to plants andanimals, FASSET Contract No FIGE-CT-2000-00102.Available from http://www.fasset.org (go to theResults page).

Some useful websites:

http://nucleardata.nuclear.lu.se/nucleardata/toi/Provides additional specialised information aboutthe nuclear properties of radioactive isotopes

http://iaeand.iaea.or.at/formmird.htmlTables of nuclear and atomic radiation fromnuclear decay and decay scheme drawings

http://www.fasset.orgFASSET (Framework for ASSessment ofEnvironmental ImpacT) - an EC 5th Frameworkproject which aims to develop a framework for theassessment of environmental impact of ionisingradiation. Contract No FIGE-CT-2000-00102.

5. References

5


Publication Content summary

Coughtrey P.J. et al. Radionuclide distribution andtransport in terrestrial and aquatic ecosystems.Balkema, 1983-1985.

A six-volume work that provides a comprehensivereview of environmental behaviour andcharacteristics of the elements.

ECORAD 2001. Proceedings of the InternationalCongress, held Aix-en-Provence, France. IPSN France,2001.

Proceedings of a conference to examine issues of theradioecology and ecotoxicology of continental andestuarine environments

Emsley, J. Nature’s building blocks: An A-Z guide tothe elements. Oxford University Press, 2001.

An introduction to the basic properties of theelements

IAEA. Protection of the environment from the effectsof ionising radiation, IAEA-TECDOC-1091. Vienna,2000.

An IAEA publication that discusses the various issuesrelating to the radiation protection of non-humanspecies.

International Commission on Radiological Protection(ICRP). 1990 recommendations of the InternationalCommission on Radiological Protection, ICRPPublication 60. Annals of the ICRP, 21(1-3), 1991.

Document currently being reviewed to specificallyaddress the protection of the environment. Revisiondue in 2005.

Martin, A. An introduction to radiation protection,4th edition. Chapman and Hall, 1996.

An introductory text that describes the basicconcepts of radiation and how systems of radiationprotection can be developed.

Nuclear Energy Agency/Organisation for EconomicCo-operation and Development (NEA/OECD).Radiological protection of the environment: the pathforward to a new policy? Workshop Proceedings,held Taormina, Sicily, Italy, 12-14 February 2002.

The proceedings of a conference that looked at theissues associated with developing a system ofradiation protection for the environment.

Pentreath, R,J. A system for radiological protection ofthe environment: some initial thoughts and ideas. J.Radiol. Prot., 19, 117-128, 1999.

A discussion of the issues relating to protection of theenvironment, including the notion that protection ofindividuals may be as important as protection ofpopulations.

Thorne, M.C. et al. A model for evaluatingradiological impacts on organisms other than manfor use in post-closure radiological assessments ofgeological repositories for radioactive wastes. JRadiol. Prot. 22(3), 249-277, 2002.

A paper that proposes a model for use in estimatingradiological doses to non-human species fromradionuclides originating in geological wasterepositories.

Van der Stricht, E. and Kirchmann, R. (editors).Radioecology: radioactivity and ecosystems. FortempsDrukkerij, LiËge, Belgium, 2001.

An introduction to radioecology - intended as alearning textbook, not a summary of the latestresearch findings.

Additional reading

The following references provide additional (and sometimes more specialised) information about theradiological consequences of radioactivity to the environment and biota:


PART 2Information on each radionuclide - listed by symbol

Symbol Radionuclide PageAm-241 Americium-241 30Ar-41 Argon-41 32Au-198 Gold-198 34Br-82 Bromine-82 36C-11 Carbon-11 38C-14 Carbon-14 40Ca-45 Calcium-45 42Ca-47 Calcium-47 44Ce-144 Cerium-144 46Cl-36 Chlorine-36 48Cm-242 Curium-242 50Cm-243 Curium-243 52Cm-244 Curium-244 54Co-57 Cobalt-57 56Co-58 Cobalt-58 58Co-60 Cobalt-60 60Cr-51 Chromium-51 62Cs-134 Caesium-134 64Cs-135 Caesium-135 66Cs-137 Caesium-137 68Depleted uranium 70Er-169 Erbium-169 72F-18 Fluorine-18 74Fe-59 Iron-59 76Ga-67 Gallium-67 78H-3 Tritium 80I-123 Iodine-123 82I-125 Iodine-125 84I-129 Iodine-129 86I-131 Iodine-131 88In-111 Indium-111 90In-113m Indium-113m 92K-40 Potassium-40 94Kr-79 Krypton-79 96Kr-81 Krypton-81 98

Symbol Radionuclide PageKr-85 Krypton-85 100La-140 Lanthanum-140 102Mn-54 Manganese-54 104Mn-56 Manganese-56 106Mo-99 Molybdenum-99 108Na-22 Sodium-22 110Na-24 Sodium-24 112Nb-94 Niobium-94 114Nb-95 Niobium-95 116Ni-59 Nickel-59 118Ni-63 Nickel-63 120Np-237 Neptunium-237 122O-15 Oxygen-15 124P-32 Phosphorus-32 126P-33 Phosphorus-33 128Pa-234m Protactinium-234m 130Pm-147 Promethium-147 132Po-210 Polonium-210 134Pb-210 Lead-210 136Pu-238 Plutonium-238 138Pu-239 Plutonium-239 140Pu-240 Plutonium-240 142Pu-241 Plutonium-241 144Ra-226 Radium-226 146Rb-81 Rubidium-81 148Rb-86 Rubidium-86 150Re-186 Rhenium-186 152Rn-222 Radon-222 154Ru-106 Ruthenium-106 156S-35 Sulphur-35 158Sb-125 Antimony-125 160Se-75 Selenium-75 162Sm-153 Samarium-153 164Sr-89 Strontium-89 166Sr-90 Strontium-90 168


Symbol Radionuclide PageTc-99 Technetium-99 170Tc-99m Technetium-99m 172Th-227 Thorium-227 174Th-228 Thorium-228 176Th-230 Thorium-230 178Th-231 Thorium-231 180Th-232 Thorium-232 182Th-234 Thorium-234 184Tl-201 Thallium-201 186

Symbol Radionuclide PageTotal alpha 188Total beta 189U-234 Uranium-234 190U-235 Uranium-235 192U-238 Uranium-238 194V-48 Vanadium-48 196Xe-133 Xenon-133 198Y-90 Yttrium-90 200Zr-95 Zirconium-95 202


Name

Radioactivehalf-life

Parent

Americium-241

432 years

Pu-241

Symbol

Principal decaymode

Daughter

Am-241

Alpha

Np-237 [R]

Origin

Grouping

Detection

Breeding

Artificial

In situ

Production, uses and modes of release

Decay modes


Production • Formed by neutron activation of uranium in a nuclear reactor, followed by decay ofthe activation products

Uses • As an alpha radiation source in smoke detectors

ModesLand

• Deposition to soils as a result of historic weapons testing• Releases from nuclear reactors or reprocessing plants

ofAir

• Releases due to weapons testing• Releases from nuclear reactors or experimental facilities release

Water • Liquid discharges from nuclear facilities

Speciation

The most important oxidation state of americiumin solution is +3, with carbonate expected to bethe dominant form.

The solubility is expected to increase as pHincreases.

Americium compounds hydrolyse in water, oftenaccompanied by colloid formation.

Analogue species

The higher actinides Am and Cm have very similarchemical, biochemical and biogeochemicalcharacteristics.

However, Am has been more extensively studiedthan Cm, so it is more appropriate to regard Amas an analogue for Cm than vice versa.

A





Terrestrial

Am-241 deposited in theterrestrial environment willmainly be transferred to soils.

Am-241 is highly particlereactive and therefore bindsstrongly to soils and sediments.

Aquatic

Am-241 is highly particlereactive in the aquaticenvironment and thereforetends to accumulate insediments.

Transport of Am-241 in aquaticsystems (e.g. saltmarsh) willtherefore be determined bysediment transport therein.

Atmospheric

Am-241 is expected to disperseas an aerosol.

The most likely chemical formwould be an oxide, but otherforms, e.g. nitrate, might alsoarise.

Environmental sink

Because of its high particlereactivity, Am-241 will tend toremain in soil systems on atimescale of decades tocenturies. Losses from the soilsystems may occur by erosion.

In aquatic systems, sedimentsare the most likelyenvironmental sink and Am-241migration will be closelyassociated with sedimenttransport.


Because of its high particle reactivity, Am-241 has a lowbioavailability to plants.

The main routes of intake by animals will typically be by ingestion ofcontaminated soil or sediment, or by inhalation.

It is also not very available to animals - uptake from thegastrointestinal tract is limited (<0.1 %), but the liver and skeletonwould act as sinks for Am-241.


Am-241 is primarily an alpha emitter.

Activity deposited on the outer layers of organisms(e.g. skin) will therefore be of little radiologicalconsequence.

Species-specific considerations

Therefore, Am-241 is of greatest potentialsignificance when internally incorporated in organsand tissues that are susceptible to the effects ofalpha radiation.

Specific consideration should be given to molluscs,crustaceans and aquatic plants, for whichconcentration factors can be a factor of 1,000 ormore higher than the surrounding water.

A


Name


Parent

Argon-41

109 minutes

N/A

Symbol

Principal decaymode

Daughter

Ar-41

Beta [gamma]

K-41

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production • Neutron activation of stable potassium-41 and argon-40 in gas-cooled nuclear reactors

Uses • No significant uses outside research activities

Modes Land • Not generally released to land

of Air • During venting of coolant gas in gas-cooled nuclear reactors

release Water • Not generally released to water

Speciation

Argon is a noble gas (it has a completely filledouter electron shell).

It forms only a limited number of chemicalcompounds due to its lack of reactivity.

Analogue species

All the noble gases (Ne, Ar, Kr, Xe and Rn) exhibitsimilar environmental behaviour.

Rn is a special case because it is generated in theenvironment from isotopes of radium and becauseit decays to produce chemically reactive, short-lived and long-lived radioactive progeny.

For this reason, Rn should not be used as adosimetric analogue for Ar.

A





Terrestrial

Ar-41 is not readily transferredto the terrestrial environment.

Aquatic

Ar-41 is not transferredsignificantly to the aquaticenvironment.

Atmospheric

Ar-41 is almost exclusivelyreleased to the atmosphere.

Its very short radioactive half-lifeand low reactivity means that itdecays almost entirely duringatmospheric transport and is nottransferred significantly to otherenvironmental media.

Environmental sink

No major sink, owing to its lackof reactivity and very short half-life.


Ar-41 is sparingly soluble in body tissues, notably those with a highfat content. However, it is not metabolised.

Some Ar-41 will be present in the lungs in inhaled air.


Ar-41 emits energetic gamma rays.

Radiation doses to organisms arise mainly due toexternal irradiation.


Because the main consideration is externalirradiation, there are no major species-dependentconsiderations.

Aquatic organisms, plant roots and burrowinganimals will be shielded, to a greater or lesserdegree, from such exposures.

A


Name


Parent

Gold-198

2.7 days

N/A

Symbol

Principal decaymode

Daughter

Au-198

Beta

Hg-198

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production • Produced by irradiating stable isotopes with neutrons or protons in a nuclearreactor or cyclotron

Uses • Used in the treatment of brain tumours and ovarian cancer

Modes Land • Sewage sludge application to land, but would probably decay away before this can occur

of Air • Not generally released to air

release Water • Could be released to sewers

Speciation

Gold is an element of the series IB metals. It showsfour oxidation states (+5, +3, +2 and +1); themost common are +3 and +1.

Gold forms a number of organometalliccompounds, as well as compounds with thehalides and oxygen.

Cyanide increases the solubility of gold and itssalts and complexes.

Analogue species

No analogue elements have been identified.

A





Terrestrial

Au-198 is not expected to bevery mobile in the environment.

Aquatic

Au-198 is likely to be particlereactive.

It is expected to decaysubstantially during its transportthrough the aquatic system.

Atmospheric

Releases of aerosols to theatmosphere could occur duringproduction or use.

Deposition of Au-198 is likely tobe limited on account of itsshort half-life.

Environmental sink

Au-198 in the terrestrialenvironment will remain in situ,either on the external surfacesof plants or on the underlyingsoil.

In aquatic systems, bottomsediments are the most likelyenvironmental sink and Au-198migration will be closelyassociated with sedimenttransport.


Ingestion of Au-198 might occur by soil fauna and herbivores.

In mammals, gold is moderately well absorbed from thegastrointestinal tract. It then becomes rapidly and relatively uniformlydistributed throughout all organs and tissues.

Plants that metabolise cyanide absorb most gold, as the cyanidehelps to solubilise the gold. Such plants include horsetails, Douglasfir, honeysuckle and Indian mustard (Brassica juncea).


Au-198 is a mixed beta-gamma emitter.

External exposure would be significant. It wouldgive rise to whole-body exposures from thegamma component and superficial exposures fromthe beta component.

Uptake in animals would give a significant beta-gamma component from internal exposure.


In mammals, the rapidity of urinary excretioncould result in doses to the wall of the urinarybladder being substantially larger than those toother organs and tissues.

For plants, consideration needs to be given tovegetation types (e.g. stands of trees) that couldintercept a substantial fraction of the dispersingplume.

A


Name


Parent

Bromine-82

35.3 hours

N/A

Symbol

Principal decaymode

Daughter

Br-82

Beta [gamma]

Kr-82

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes



Uses • Used as a tracer for exchangeable chloride and for measurements of extracellularfluid properties




Speciation

Bromine is a halogen element that shows apredominant oxidation state of -1.

It is very reactive and forms bromide compoundswith many other elements.

It also forms a series of bromate compoundsinvolving bromine and oxygen.

Analogue species

Chlorine is the most appropriate analogue.

However, as chlorine is an essential element for allplants and animals and bromine is not, thisanalogy should be used with caution.

B





Terrestrial

Bromide is not particle reactiveand so may be expected tomove freely through theterrestrial environment.

The very short half-life will limitthe extent to which it canmigrate in the terrestrialenvironment.

Aquatic

Bromide will behaveconservatively in aquaticsystems.

The very short half-life will limitthe extent to which it canmigrate in the terrestrialenvironment.

Atmospheric

Br-82 could be released to theatmosphere.

It is dispersed either as areactive vapour or an aerosol,but the very short half-life mayprevent wet and dry deposition.

Br-82 in bromide also reactswith atmospheric oxygen.

Environmental sink

Br-82 will either decay in situ (ifit is retained in plants or takenup by animals) or it will decayas it disperses in surface watersand groundwaters.


Plants can take up Br-82 by direct foliar absorption, after which it isdispersed relatively uniformly throughout their tissues. Plants mayalso take up bromide through their roots, via soil water.

Animals will take up Br-82 from plants and water bodies. Bromine isessentially completely absorbed from the gastrointestinal tract ofmammals and is relatively uniformly distributed throughout allorgans and tissues of the body.

Br-82 is highly bioavailable to aquatic organisms, namely aquaticplants.

The very short half-life of Br-82 will limit the accumulation process.


Br-82 is a beta emitter and, in addition, a strongemitter of energetic gamma rays.

Organisms will be subjected to external irradiationfrom gamma rays, and gamma rays from internallyincorporated Br-82.

The beta particle will also make a smallcontribution to dose.


Br-82 is thought to be highly bioavailable to awide range of plant and animal species.

B


Name


Parent

Carbon-11

20 minutes

N/A

Symbol

Principal decaymode

Daughter

C-11

Beta [gamma]

B-11

Origin

Grouping

Detection

Activation

Artificial

Laboratory


Decay modes



Uses • Labelling of organic compounds in biomedical studies

ModesLand • Sewage sludge application to land, but would probably decay away long

before this can occurof

Air • Not generally released to air release

Water • Could be released to sewers

Speciation

The majority of compounds of carbon are in the+4 oxidation state.

Its chemistry is characterised by its tendency toform stable bonds with oxygen, hydrogen, halides,nitrogen, sulphur and other carbon atoms.

In solution, the carbonate and bicarbonate ionspredominate.

Analogue species

Because of its fundamental role in biochemistryand biogeochemistry, there are no other elementsthat can be considered as environmentalanalogues of carbon.

However, studies of stable carbon behaviour in theenvironment and of distinctions in behaviour of itstwo stable isotopes (C-12 and C-13) provideimportant insights into the environmentalbehaviour of radioactive isotopes of carbon.

C





Terrestrial

The very short radioactive half-life of C-11 precludes significanttransport in terrestrialenvironments.

Aquatic

The very short radioactive half-life of C-11 precludes significanttransport in aquaticenvironments.

Atmospheric

The very short radioactive half-life of C-11 precludes significanttransport in atmosphericenvironments.

Environmental sink

Almost all C-11 will be lost byradioactive decay during itsdispersion from the source.

Almost all that is taken up byplants will decay at the site ofphotosynthesis.

C-11 that is taken up byanimals will rapidly becomerelatively uniformly distributedthroughout the body and decayin situ.


There is a limited potential for uptake into plants for photosynthesisand into animals by respiration following an atmospheric release.

There is little possibility of significant intake and uptake following anaquatic release.


C-11 emits positrons. These, in turn, generateannihilation radiation in the form of 0.511 MeVphotons.

Uptake into plants could give rise to irradiation byboth beta and gamma radiation. This irradiationwould be expected to be mainly of above groundparts.

Internal irradiation of animals would also be frombeta and gamma irradiation from C-11 distributedreasonably uniformly throughout all organs andtissues of the body.


No specific issues on account of the very shorthalf-life of C-11.

C


Name


Parent

Carbon-14

5,730 years

N/A

Symbol

Principal decaymode

Daughter

C-14

Beta

N-14

Origin

Grouping

Detection

Cosmogenic

Natural

Laboratory


Decay modes


Production • Naturally in the upper atmosphere due to cosmic ray interactions• In nuclear reactors by neutron irradiation of carbon and nitrogen

Uses • Radiocarbon dating• Diagnostic medical procedures (e.g. studies of gigantism)

ModesLand • Deposition of fallout from a nuclear accident or natural processes

of Air• Naturally present through cosmic ray interactions• Historic weapons testing

releaseWater

• Transfer from atmosphere to shallow and deep ocean waters• Liquid discharges from nuclear facilities

Speciation

The majority of compounds of carbon are in the+4 oxidation state.

Its chemistry is characterised by its tendency toform stable bonds with oxygen, hydrogen, halides,nitrogen, sulphur and other carbon atoms.

In solution, the carbonate and bicarbonate ionspredominate.

Analogue species

Because of its fundamental role in biochemistryand biogeochemistry, there are no other elementsthat can be considered as environmentalanalogues of carbon.

However, studies of stable carbon behaviour in theenvironment and of distinctions in behaviour of itstwo stable isotopes (C-12 and C-13) provideimportant insights into the environmentalbehaviour of radioactive isotopes of carbon.

C





Terrestrial

C-14 is rapidly dispersedthrough terrestrial environmentsby a wide variety of biological,biochemical andbiogeochemical processes.

For disperse sources, this resultsin similar specific activities fordifferent components of theenvironment.

Aquatic

C-14 is rapidly dispersedthrough aquatic environments.

Atmospheric

C-14 is mainly released to, orproduced in, the atmosphere.

It then becomes globallydispersed on a timescale ofmonths to a few years, i.e. verymuch shorter than itsradioactive half-life.

Environmental sink

Long-term sinks are deep oceanwaters and the deposition ofcarbonaceous sediments.

On shorter time scales, biotacan constitute a sink or source,depending on whether theamount of standing biomass isincreasing or decreasing.


Plants take up C-14 mainly for photosynthesis (and lose it byrespiration as carbon dioxide).

However, a limited degree of root uptake also occurs and a fewpercent of plant carbon can derive from the soil rather than theabove ground atmosphere.

Animals are mainly exposed to C-14 by ingestion. In the short-term,uptake will be highest in metabolically active tissues, but this tendsto be compensated for in the longer term by higher rates of turnoverin such tissues.


C-14 is a soft beta emitter that becomes relativelyuniformly distributed throughout all organs andtissues in both plants and animals.

Because it is a pure soft beta emitter, dose ratesare entirely determined by concentrations near thepoint of exposure.


If localised releases occur to freshwaters with smalldilution volumes or flow rates, specificconsideration should be given to the very highdegree of uptake that can occur in fish (IAEA,1994).

C


Name


Parent

Calcium-45

163 days

N/A

Symbol

Principal decaymode

Daughter

Ca-45

Beta

Sc-45

Origin

Grouping

Detection

Activation

Artificial

Laboratory


Decay modes


Production • Neutron irradiation of stable precursors in a cyclotron or nuclear reactor

Uses • Used in medicine as a tracer to investigate calcium metabolism

Modes Land • Sewage sludge application to land.


release Water • Hospital releases to sewers

Speciation

Calcium is an alkaline earth element and, asconsequence, the most important species is theCa2+ ion.

Isotopes of calcium can therefore be expected totake part in a number of precipitation andsubstitution reactions.

Precipitation as sulphate or carbonate is possible.

Analogue species

Sr is a close chemical analogue.

Although Ca is an essential element for almost allbiota, the extensive studies of Sr-90 in theenvironment can sometimes provide usefulinformation about the chemistry, biochemistry andbiogeochemistry of Ca.

C





Terrestrial

Ca-45 deposited to soils isexpected to be relatively mobileand thus available for uptake byplants.

Aquatic

Ca-45 can exhibit a relativelyhigh degree of sorption toaquatic sediments and aquatictransport will thus be governedby movement of sediments.

Atmospheric

If released to the atmosphere,Ca-45 would be present as anaerosol.

Atmospheric transport wouldresult in wet and dry depositionto plants and soils.

Environmental sink

The relatively short half-life ofCa-45 means that it is likely todecay close to its site ofdeposition in terrestrialenvironments.

Substantial dispersion is likely inaquatic environments, withdecay either in the watercolumn or in depositedsediments.


Ca-45 is moderately bioavailable to plants. Foliar uptake can besignificant.

Calcium is moderately bioavailable to animals, with a fractionalgastrointestinal absorption of ~30 %. It will be translocated mainly tomineral bone, skeleton and carapace.

Concentrations in soft tissues are likely to be at least two orders ofmagnitude lower than concentrations in bone.

The bioavailability of Ca to animals is high (fractional gastrointestinalabsorption ~30 %).

Concentrations of Ca will be low for marine fish, but can be quitehigh for freshwater fish and marine invertebrates.


Ca-45 is a soft beta emitter. Therefore, onlyinternal irradiation is relevant.

Relatively high doses will occur to cells embeddedin, or present on the surfaces of, mineralisedtissues.


Discharges to freshwaters should be given specificconsideration because of the high concentrationratios appropriate to freshwater fish.

C


Name


Parent

Calcium-47

163 days

N/A

Symbol

Principal decaymode

Daughter

Ca-47

Beta

Sc-47 [R]

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production • Activation of stable calcium-46 by neutrons in nuclear reactors





Speciation

Calcium is an alkaline earth element and, asconsequence, the most important species is theCa2+ ion.

Isotopes of calcium can therefore be expected totake part in a number of precipitation andsubstitution reactions.

Precipitation as sulphate or carbonate is possible.

Analogue species

Sr is a close chemical analogue.

Although Ca is an essential element for almost allbiota, the extensive studies of Sr-90 in theenvironment can sometimes provide usefulinformation about the chemistry, biochemistry andbiogeochemistry of Ca.

C





Terrestrial

Ca-47 added to soils is expectedto be relatively mobile and thusavailable for uptake by plants.

Aquatic

Ca-47 can exhibit a relativelyhigh degree of sorption toaquatic sediments and aquatictransport will thus be governedby movement of sediments.

Atmospheric

If released to the atmosphere,Ca-47 would be present as anaerosol.


Environmental sink

The short half-life of Ca-47means that it is likely to decayclose to its site of deposition interrestrial environments.

Substantial dispersion is likely inaquatic environments, withdecay either in the watercolumn or in depositedsediments.


Ca-47 is moderately bioavailable to plants. Foliar uptake can besignificant.

Calcium is moderately bioavailable to animals, with a fractionalgastrointestinal absorption of ~30 %. It will be translocated mainly tomineral bone, skeleton and carapace. Because of its short half-life,only limited accumulation in bone is expected.

The bioavailability of Ca to animals is high (fractional gastrointestinalabsorption ~30 %).

Concentrations of Ca will be low for marine fish, but can be quitehigh for freshwater fish and marine invertebrates.


Ca-47 is a mixed beta-gamma emitter.

External irradiation from the plume or initialterrestrial deposits may be more important thaninternal uptake by terrestrial biota because of theshort half-life of the radionuclide.


No special considerations on account of the shorthalf-life of Ca-47.

C


Name


Parent

Cerium-144

285 days

N/A

Symbol

Principal decaymode

Daughter

Ce-144

Beta

Pr-144 [R]

Origin

Grouping

Detection

Fission

Artificial

In situ


Decay modes


Production • Produced during fission in a nuclear reactor


Modes Land • During treatment and disposal of spent fuel

of Air • During treatment and disposal of spent fuel

release Water • During treatment and disposal of spent fuel• Liquid discharges from nuclear facilities

Speciation

Cerium is a rare-earth element that showsoxidation states of +3 and +4.

As such, cerium forms compounds with hydrogen,oxygen and the halides. It also forms stablecomplexes.

Analogue species

The rare earth elements (Ce, Pr, Nd, Pm, Sm, Eu,Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) exhibit similarchemical, biochemical and biogeochemicalcharacteristics. However, these characteristicschange systematically in the group with increasingatomic number. Cerium is one of the best-studiedmembers of the group.

Analogies with other members of the group andwith higher actinides such as Am can be useful.

C





Terrestrial

Ce-144 is highly particlereactive and hence wouldremain bound to soil particlesand on the surfaces of plants.

Transfers from plant to soil andbulk movement of soils wouldbe the main transportmechanisms.

Aquatic

Ce-144 is highly particlereactive. It is likely to bind tosuspended sediments.

Atmospheric

If released to the atmosphere,Ce-144 would be present as anaerosol, probably as the oxide.


Environmental sink

The relatively short half-life andhigh particle reactivity of Ce-144 mean that it is likely todecay close to its site ofdeposition in terrestrialenvironments.

In aquatic environments,bottom sediments close to thesource of release may form animportant sink.


Ce-144 is not very bioavailable to animals. The fractionalgastrointestinal absorption is typically <0.1 %. Any Ce-144 that isabsorbed is mainly deposited in the liver and skeleton.

Intake by terrestrial animals is likely to be mainly by ingestion of Ce-144 present on the exterior surfaces of plants or deposited on soil.Very little uptake from the gastrointestinal tract is anticipated, exceptperhaps in pre-weaned animals.

In the aquatic environment, uptake by fish and invertebrates ismainly direct from the water rather than from food. Uptake byaquatic plants is likely to be by surface adsorption.


Ce-144 is a mixed beta-gamma emitter.

External irradiation from activity deposited in theterrestrial environment could be of greaterimportance than internal exposure.


In mammals and birds, the walls of thegastrointestinal tract are likely to receivesubstantially higher doses than other organs andtissues. This is due to irradiation by unabsorbedCe-144 passing through the tract.

C


Name


Parent

Chlorine-36

3.01 x 105yrs

N/A

Symbol

Principal decaymode

Daughter

Cl-36

Beta

Ar-36

Origin

Grouping

Detection

Cosmogenic

Natural

Laboratory


Decay modes


Production • Cosmic ray interactions in the upper atmosphere• Neutron irradiation of residual chlorine in reactor graphite rods

Uses • Radiological dating of sediment and glacial deposits

Modes Land • Treatment and disposal of spent fuel and reactor hardware

of Air • Treatment and disposal of spent fuel and reactor hardware

release Water • Treatment and disposal of spent fuel and reactor hardware

Speciation

Chlorine is a halogen element.

It shows an oxidation state of -1 in chloridecompounds, and states of +1 and others inchlorate compounds (these contain chlorine andoxygen).

In environmental situations, the chloride speciesare of greatest importance.

Analogue species

There are chemical similarities between F, Cl, Brand I. However, the biochemical roles andbehaviour of these elements are very different.

The only chemical analogue to Cl-36 is perhapsthe stable Cl element.

C





Terrestrial

Cl-36 is of greatest interestwhen it contaminates soils. Itexhibits the highest plant:soilconcentration ratio of anyradionuclide.

In contaminated soils, themajority of the Cl-36 may havebeen translocated to plantswithin a few weeks.

Aquatic

Cl-36 is highly conservative inwaters and is, therefore, readilytransported through the aquaticenvironment.

It may be rapidly dispersed inwater bodies or enter the soilsystem.

Atmospheric

If released to atmosphere, Cl-36would be expected to be widelydispersed and readilybioavailable to both plants andanimals.

Environmental sink

Cl-36 disperses into the largepool of stable chloride that ispresent in the environment.

As chloride is mobile ingroundwaters and surfacewaters, the Cl-36 will tend tomigrate in the long-term to themarine environment anddisperse throughout the worldísoceans.


Cl-36 is highly accumulated by plants from soils. Cl-36 present in thisplant material is then highly bioavailable to animals.

These terrestrial foodchain pathways are thought to be of greaterimportance than aquatic pathways due to the rapid dilution anddispersion of Cl-36 in surface waters and the limited degree ofconcentration even by freshwater organisms.


Cl-36 is a pure beta emitter.

It is relatively uniformly distributed throughoutplant and animal body tissues.

For dosimetric purposes, it is often useful to adopta specific activity model in which the ratio of Cl-36to stable chlorine is assumed to be the same insource and receptor components of theenvironment.


No major species-specific considerations arisebecause chlorine is ubiquitously present in plantand animal tissues, and is relatively uniformlydistributed throughout them.

C


Name


Parent

Curium-242

163 days

Am-242

Symbol

Principal decaymode

Daughter

Cm-242

Alpha

Pu-238 [R]

Origin

Grouping

Detection

Breeding

Artificial

Laboratory


Decay modes


Production • Successive capture of neutrons by plutonium and americium in a nuclear reactor,followed by decay of the products

Uses • Source of power in satellites and other space equipment• Source of alpha particles for analysis of moon surface

Modes Land • Deposition following atmospheric testing of nuclear weapons• As a result of nuclear accidents and releases from nuclear facilities

of Air • Atmospheric testing of nuclear weapons

release Water • Leaching from soils to groundwater

Speciation

Most curium compounds are based on anoxidation state of +3.

For example, it forms trihalide compounds (e.g.CmF3), although compounds such as CmO2 areexamples of the +4 oxidation state.

Curium and its compounds are capable of theformation and precipitation of colloids and organiccomplexes.

Analogue species

The two higher actinides, Am and Cm, have verysimilar chemical, biochemical and biogeochemicalcharacteristics.

However, Am has been more extensively studiedthan Cm, so it is appropriate to regard Am as ananalogue for Cm.

C





Terrestrial

Cm-242 is highly particlereactive and therefore bindsstrongly to soils and sediments.

It is strongly excluded fromplants and is mainly present ontheir surfaces as externalcontamination.

It is also not very available toanimals

Aquatic

Cm-242 is highly particlereactive in the aquaticenvironment and thereforetends to be accumulated in thebottom sediments.

Atmospheric

Cm-242 would be expected todisperse as an aerosol.


Environmental sink

Cm-242 deposited in theterrestrial environment willmainly be transferred to soils.

It will tend to remain in suchsoil systems until it decays.

In aquatic systems, bottomsediments are the most likelyenvironmental sink and Cm-242migration will be closelyassociated with sedimenttransport


Because of its high particle reactivity, Cm-242 shows lowbioavailability to plants.

The main routes of intake by animals will typically be by ingestion ofcontaminated soil or sediment, or by inhalation (e.g. re-suspendedsoils and sediments).

Although uptake from the gastrointestinal tract is limited (<0.1 %),enhanced concentrations of Cm-242 may occur in the liver andskeleton.

Marine and freshwater fish concentrations are about a factor of 50higher than concentrations in water. Concentrations in molluscs,crustaceans and marine plants can be a factor of 1,000 higher thanthe surrounding water.


Cm-242 is primarily an alpha emitter.


Cm-242 is of greatest potential significance wheninternally incorporated in organs and tissues thatare susceptible to the effects of alpha radiation.


Specific consideration should be given to molluscs,crustaceans and marine plants for whichconcentration factors can be a factor of 1,000 ormore higher than the surrounding water.

C


Name


Parent

Curium-243

28.5 years

N/A

Symbol

Principal decaymode

Daughter

Cm-243

Alpha

Pu-239 [R]

Origin

Grouping

Detection

Breeding

Artificial

Laboratory


Decay modes



Uses • No specific use other than research activities

Modes Land• Deposition following atmospheric testing of nuclear weapons• As a result of nuclear accidents and releases from nuclear facilities

ofAir • Atmospheric testing of nuclear weapons

releaseWater • Leaching from soils to groundwater

Speciation

Most curium compounds are based on anoxidation state of +3 for curium.



Analogue species



C





Terrestrial




Aquatic

Cm-243 is highly particlereactive in the aquaticenvironment and thereforetends to accumulate in thebottom sediments.

Atmospheric



Environmental sink



In aquatic systems, bottomsediments are the most likelyenvironmental sink and Cm-243migration will be closelyassociated with sedimenttransport.








Activity deposited on the outer layers oforganisms (e.g. skin) will therefore be of littleradiological consequence.



Specific consideration should be given to molluscs,crustaceans and aquatic plants for whichconcentration factors can be a factor of 1,000 ormore higher than the surrounding water.

C


Name


Parent

Curium-244

18.1 years

Cf-248

Symbol

Principal decaymode

Daughter

Cm-244

Alpha

Pu-240 [R]

Origin

Grouping

Detection

Breeding

Artificial

Laboratory


Decay modes



Uses • No specific use other than research activities

Modes Land• Deposition following atmospheric testing of nuclear weapons• As a result of nuclear accidents and releases from nuclear facilities

ofAir • Atmospheric testing of nuclear weapons

releaseWater • Leaching from soils to groundwater

Speciation

Most curium compounds are based on anoxidation state of +3 for curium.



Analogue species



C





Terrestrial




Aquatic

Cm-244 is highly particlereactive in the aquaticenvironment and thereforetends to accumulate in thebottom sediments.

Atmospheric



Environmental sink



In aquatic systems, bottomsediments are the most likelyenvironmental sink and Cm-244migration will be closelyassociated with sedimenttransport.








Activity deposited on the outer layers (e.g. skin) oforganisms will therefore be of little radiologicalconsequence.



Specific consideration should be given to molluscs,crustaceans and aquatic plants for whichconcentration factors can be a factor of 1,000 ormore higher than the surrounding water.

C


Name


Parent

Cobalt-57

271 days

Cf-248

Symbol

Principal decaymode

Daughter

Co-57

EC

Fe-57

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production • Neutron activation of other transition metals present in the structural steelsof reactor vessels

Uses • In medicine for diagnostic purposes




Speciation

Cobalt is a transition metal element that showstwo common oxidation states (+2 and +3).

In the +2 state, it forms a wide range of ioniccompounds including the oxide, hydroxide andhalides.

In the +3 oxidation state, it forms a wide range ofcomplexes.

Analogue species

Cobalt is an essential element for animals becauseof its central role in vitamin B12.

Therefore, whereas analogies with other transitionmetals may be made for plants, this is not thoughtto be appropriate for animals.

C





Terrestrial

Co-57 is highly particle reactiveand tends to be absorbed to thesurface of clay minerals throughiron and manganese oxides.

It can be mobile in organic oracid soils, but tends to beimmobile in alkaline or neutralsoils.

Aquatic

Co-57 is highly reactive withaquatic sediments and tends tobe migrate from the watercolumn to bottom sediments.

Atmospheric

Co-57 would be expected todisperse as an aerosol.

The most likely chemical formwould be an oxide, but otherforms, e.g. chloride, might alsoarise

Environmental sink

As Co-57 has a half-life of only271 days and is highly particlereactive, it can be expected tobe retained in terrestrial soilsand sediments, and to decay insitu.

In the aquatic environment, Co-57 will either decay in thewater column or in bottomsediments close to its point ofdeposition.


Root uptake by plants is not a significant uptake mechanism for Co-57.

Cobalt is moderately bioavailable to animals, with a fractionalgastrointestinal absorption of ~20 %.

Animal intakes will be mainly by ingestion of contaminated plants,with a secondary contribution from soil consumption.

Concentrations in aquatic plants, molluscs and crustaceans are about1,000 higher than the surrounding water.

Concentration ratios in freshwater fish relative to water vary fromabout 10 to 1,000 or more. However, values for marine fish aretypically about 1.


Co-57 emits gamma rays following decay byelectron capture.

As Co-57 is relatively uniformly distributed in plantand animal tissues, gamma doses to all organs andtissues will be similar.


The high concentration ratios exhibited by manyaquatic organisms may mean that these are ofparticular interest.

C


Name


Parent

Cobalt-58

71 days

N/A

Symbol

Principal decaymode

Daughter

Co-58

Beta [gamma]

Fe-58

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production • Neutron activation of other transition metals present in the structural steelsof reactor vessels

Uses • In medicine for diagnostic purposes




Speciation




Analogue species



C





Terrestrial



Aquatic


Atmospheric



Environmental sink

As Co-58 has a half-life of only71 days and is highly particlereactive, it can be expected tobe retained in terrestrial soilsand sediments, and to decay insitu.









Co-58 is a beta-gamma emitter.




C


Name


Parent

Cobalt-60

5.27 years

Co-60m

Symbol

Principal decaymode

Daughter

Co-60

Beta [gamma]

Ni-60

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production • Neutron activation of stable cobalt-59 present in the structural steelsof reactor vessels

Uses• Detection of flaws in welded joints and castings• In medicine as an irradiation source in the treatment of cancer

ModesLand • Treatment and disposal of spent fuel and reactor hardware

ofAir • Treatment and disposal of spent fuel and reactor hardware

release Water• Treatment and disposal of spent fuel and reactor hardware• Liquid discharges from nuclear facilities

Speciation




Analogue species



C





Terrestrial



Aquatic


Atmospheric



Environmental sink

As Co-60 is highly particlereactive, it can be expected tobe retained in terrestrial soilsand sediments, and to decay insitu.









Co-60 is a beta-gamma emitter.




C


Name


Parent

Chromium-51

27.7 days

N/A

Symbol

Principal decaymode

Daughter

Cr-51

EC

V-51

Origin

Grouping

Detection

Activation

Artificial

Laboratory


Decay modes


Production • Neutron activation of non-radioactive precursors in a cyclotron or nuclear reactor

Uses• In medicine as a tracer to label red blood cells• To assist in the treatment of bone cancer

Modes Land • Sewage sludge application to land.



Speciation

Chromium is a transition metal that can show alloxidation states from -2 through to +6.

The chemistry of chromium and its compounds istherefore very wide and varied.

Chromium has a number of oxides, formscompounds with the halogens, and can formorganic complexes.

Analogue species

Cr has been extensively studied in its own right,both as an essential trace element and as achemical carcinogen. Therefore, there is no needto rely on analogues to characterise its behaviour.

Cr has some chemical, biochemical andbiogeochemical affinities with the other transitionmetals. However, these affinities are not very close.

C





Terrestrial

Uptake of Cr by plants fromsoils is limited. Taking intoaccount the short half-life of Cr-51, external deposition onplants is of greatest interest.

The availability of Cr to animalsis low for trivalent forms butmoderate for hexavalent forms.

Aquatic

The degree of interaction of Crwith sediments depends onchemical form.

Trivalent Cr is highly sorbed,whereas hexavalent Cr is lessstrongly sorbed and asubstantial fraction can remainin solution.

Atmospheric

If Cr-51 was released toatmosphere, it would probablybe as an aerosol.

Environmental sink

The short half-life of Cr-51means that it will often decayclose to its point of depositionin terrestrial environments.

In aquatic environments,trivalent Cr-51 is likely to decayin bottom sediments.

However, hexavalent Cr-51 maybe widely dispersed and mainlydecay in the water column.


Uptake of Cr by plants from soils is limited. Taking into account theshort half-life of Cr-51, external deposition on plants is of greatestinterest.

The availability of Cr to animals is low for trivalent forms butmoderate for hexavalent forms and Cr incorporated into foodstuffs.

Cr-51 exhibits variable, but often high concentration ratios relative towater in aquatic organisms (typically from a few hundred to a fewthousand).

Cr-51 is likely to be widely distributed throughout the tissues of bothterrestrial and aquatic organisms.


Cr-51 emits a gamma ray of moderate energy inabout 10 % of its transformations.

As Cr-51 is uniformly distributed through allorgans and tissues, the overall dose will beuniformly distributed through the body.


The conservative behaviour of hexavalent Cr-51 inaquatic systems and the high concentration ratiosrelative to water for Cr-51 of many aquaticorganisms make these species of particular interest.

CC


Name


Parent

Caesium-134

2.06 years

N/A

Symbol

Principal decaymode

Daughter

Cs-134

Beta [gamma]

Ba-134

Origin

Grouping

Detection

Fission

Artificial

In situ


Decay modes


Production • As a result of fission processes in a nuclear reactor

Uses • Uses for scientific research

Modes Land • Deposition following weapons tests or a nuclear accident

of Air • Discharge to air following weapons tests or a nuclear accident

release Water • Discharge to the sea from operating nuclear facilities

Speciation

Caesium is an alkali metal whose chemicalbehaviour is determined by the properties of theCs+ ion.

Most of the compounds of caesium are ionic innature, although more complex species can beformed.

Caesium reacts extremely vigorously with water,oxygen and halogens.

Analogue species

Cr has been extensively studied in its own right,both as an essential trace element and as achemical carcinogen. Therefore, there is no needto rely on analogues to characterise its behaviour.

Cr has some chemical, biochemical andbiogeochemical affinities with the other transitionmetals. However, these affinities are not very close.

C





Terrestrial

Cs-134 binds strongly to theclay fraction in soils andsediments.

However, it can also berelatively highly available forplant uptake, particularly inorganic and K-deficient soils.

Cs-134 is transferred from plantsurfaces to soils in around 5-30days.

Aquatic

Cs-134 is moderately particlereactive in marineenvironments, so dispersion inwaters and loss to bottomsediments are both possible.

In freshwaters, Cs-134 can bemore highly particle reactiveand subject to local deposition.

Atmospheric

Cs is a highly volatile element.Thus, Cs-134 is likely to be ofimportance in atmosphericreleases from nuclear accidents.

It would be released anddispersed as an aerosol.

Environmental sink

The high particle reactivity ofCs-134 means that it is likely todecay close to its site ofdeposition in terrestrialenvironments.

In aquatic environments, Cs-134 can be widely dispersedand may decay either in thewater column or in depositedsediments.


Cs-134 can be relatively highly available for plant uptake, particularlyin organic and K-deficient soils.

Cs-134 is highly bioavailable to animals and is almost completelyabsorbed from the gastrointestinal tract.

It distributes reasonably uniformly through most organs and tissuesof the body, but concentrates to some degree in muscle.

Concentration ratios relative to water are about 100 for marine fish,30-50 for marine invertebrates and plants, but about 1,000 forfreshwater fish.

Muscle is the primary site of deposition in freshwater fish.


The main emissions from Cs-134 are moderatelyenergetic gamma rays.

Therefore, external irradiation, e.g. from soils andsediments, can be important.

The relatively uniform distribution of Cs-134 inbiota and the penetrating power of the emittedgamma rays mean that individual organ and tissuedoses are generally of comparable magnitude tothe average whole-body dose.


The high concentration ratios for freshwater fishmake the exposure of freshwater fish appropriatefor specific consideration.

Plant uptake in K-deficient areas or areas withorganic soils subject to wet deposition is also ofpotential importance.

Uptake in animals grazing such areas also needs tobe considered.

C


Name


Parent

Caesium-135

2.3 x 106 years

N/A

Symbol

Principal decaymode

Daughter

Cs-135

Beta

Ba-135

Origin

Grouping

Detection

Fission

Artificial

Laboratory


Decay modes



Uses • No specific uses, except for scientific research

Modes Land • Deposition following weapons tests or a nuclear accident

of Air • Discharge to air following weapons tests or a nuclear accident

release Water • Discharge to the sea from operating nuclear facilities

Speciation




Analogue species

Cs exhibits many chemical, biochemical andbiogeochemical similarities to K.

Cs:K ratios have often been used to characterisethe environmental behaviour of Cs.

C





Terrestrial



Cs-135 is translocated fromplant surfaces to soils in around5-30 days

Aquatic

Cs-135 is moderately particlereactive in marineenvironments, so dispersion inwaters competes effectively withloss to bottom sediments.


Atmospheric



Environmental sink






It distributes reasonably uniformly throughout all organs and tissuesof the body, but concentrates to some degree in muscle.




Cs-135 is a soft beta emitter.

Therefore, external exposure is of no importance.

Because Cs-135 is relatively uniformly distributedin tissues, doses to individual organs and tissuesare of comparable magnitude to average whole-body doses.





CC


Name


Parent

Caesium-137

30 years

N/A

Symbol

Principal decaymode

Daughter

Cs-137

Beta [gamma]

Ba-137m [R]

Origin

Grouping

Detection

Fission

Artificial

In situ


Decay modes



Uses• As a radiation source in the treatment of cancer (brachytherapy)• For detecting cracks and imperfections in metal structures

Modes Land• Deposition following weapons tests or a nuclear accident• Disposal of medical sources

ofAir • Discharge to air following weapons tests or a nuclear accident

releaseWater • Discharge to the sea from operating nuclear facilities

Speciation




Analogue species

Cs exhibits many chemical, biochemical andbiogeochemical similarities to K.

Cs:K ratios have often been used to characterisethe environmental behaviour of Cs.

C





Terrestrial



Cs-137 is translocated fromplant surfaces to soils in around5-30 days

Aquatic

Cs-137 is moderately particlereactive in marineenvironments, so dispersion inwaters competes effectively withloss to bottom sediments.


Atmospheric



Environmental sink






It distributes reasonably uniformly throughout all organs and tissuesof the body, but concentrates to some degree in muscle.




The main emissions from Cs-137 and its veryshort-lived daughter Ba-137m are beta particlesand moderately energetic gamma rays.

Therefore, external irradiation (e.g. from soils andsediments) can be important.

The relatively uniform distribution of Cs-137 inbiota means that individual organ and tissue dosesare of comparable magnitude to the averagewhole-body dose.





CC


Name


Parent

Depleted uranium

4.46 x 109 years

N/A

Symbol

Principal decaymode

Daughter

Depleted uranium

Alpha

U-234 [R]

Origin

Grouping

Detection

Primordial

Natural

In situ


Decay modes


Production

• By removal of much but not all uranium-235 from uranium ore through theproduction of uranium hexafluoride, followed by conversion to other chemicalforms, e.g. uranium oxide or uranium metal

Uses• Use as tank armour and armour piercing projectiles• As a material for radiation shielding

Modes Land • From military testing or application on the battlefield

of Air • As an aerosol from military testing or application on the battlefield


Speciation

Uranium can exist in any one of four oxidationstates, with the +4 state being favoured inreducing conditions and the +6 state in oxidisingconditions.

Uranium forms a wide range of halide and oxidecompounds. The hydroxide and carbonate are alsoknown, and uranium can participate in theformation of organic complexes.

U is a ‘chemical’ problem rather than a‘radiotoxicity’ problem.

Analogue species

Depleted U is uranium in which the proportion ofU-235 is reduced, typically by a factor of 3 or 4.However, its chemical characteristics areunchanged.

For this reason, there is no requirement to identifyanalogue elements (see the entry for U-238).

D





Terrestrial

Uranium is not stronglyadsorbed to soils.

However, its behaviour is redoxsensitive and it can accumulatein reducing horizons.

In general, it is stronglyexcluded from plants.

Aquatic

Uranium behaves conservativelyin aqueous environments.

It is not strongly accumulatedby aquatic organisms.

Atmospheric

U-238 released to atmospherewould be expected to disperseas an aerosol.

Oxide forms would dominate ifthe release was due tobattlefield activities.

Environmental sink

Depleted U entering theenvironment due to humanactivities may be mobile,migrating through the aqueousenvironment.


In general, uranium is strongly excluded from plants, although graincan show greater accumulation of uranium than other plant types.

Intakes from plant material and in soil are likely to be of comparableimportance for animals.

Uranium is not very bioavailable to animals -- the fractionalgastrointestinal absorption is typically 1-%2 %. Mineral bone is theprincipal site of accumulation.

Concentration ratios relative to water are about 10 for freshwaterand marine fish and crustaceans. Concentration ratios for molluscscan be a little higher (~30) and values ~100 are typical of marineplants.


Depleted uranium is primarily an alpha emitter.


Therefore, depleted uranium is of greatestpotential significance when internally incorporatedin organs and tissues that are susceptible to theeffects of alpha radiation.


No species-specific considerations

D


Name


Parent

Erbium-169

9.4 days

N/A

Symbol

Principal decaymode

Daughter

Er-169

Beta

Tm-169

Origin

Grouping

Detection

Activation

Artificial

Laboratory


Decay modes






release Water • During treatment and disposal of spent fuel

Speciation

Erbium is a rare-earth element that shows anoxidation state of +3.

As such, erbium forms compounds with hydrogen,oxygen and the halides. It also forms stablecomplexes.

Analogue species


Analogies with other members and with higheractinides, such as Am, can be useful.

E





Terrestrial

Er-169 is highly particle reactive,and hence would remain boundto soil particles and on thesurfaces of plants.


Aquatic

Er-169 is highly particle reactive.It is likely to bind to suspendedsediments close to its point ofdischarge.

It may be rapidly lost bydeposition from the watercolumn to sediments.

Atmospheric

If Er-169 was released to theatmosphere, it would be as anaerosol.

Environmental sink

The short half-life and highparticle reactivity of Er-169mean that it is likely to decayclose to its site of deposition interrestrial environments.



Er-169 is not very bioavailable to animals. The fractionalgastrointestinal absorption is typically <0.001. Any Er-169 that isabsorbed is mainly deposited in the liver and skeleton.

Intake by terrestrial animals is likely to be mainly the ingestion of Er-169 present on the exterior surfaces of plants or deposited on soil.

Very little uptake from the gastrointestinal tract is anticipated, exceptperhaps in pre-weaned animals.

In the aquatic environment, uptake by fish and invertebrates ismainly direct from the water rather than food. Uptake by aquaticplants is likely to be by surface adsorption.


Er-169 is primarily a beta emitter, with negligibleemission of gamma rays.

This means that only superficial tissues (to a depthof a few millimetres) will be exposed from externalirradiation.

Internal irradiation will be limited because of thelow bioavailability of Er-169.


In mammals and birds, the walls of thegastrointestinal tract are likely to receivesubstantially higher doses than other organs andtissues.

E


Name


Parent

Fluorine-18

110 minutes

N/A

Symbol

Principal decaymode

Daughter

F-18

Beta [gamma]

O-18

Origin

Grouping

Detection

Activation

Artificial

Laboratory


Decay modes


Production • Irradiation of stable precursors with neutrons in a nuclear reactor or cyclotron

Uses • In medical diagnosis using positron emission tomography




Speciation

Fluorine is a halogen element that shows a singleoxidation state of -1.

It is extremely reactive and forms compounds withmost other elements, with the exception of thenoble gases.

Analogue species

Although fluorine could be considered analogousto chlorine and iodine, this is of little relevance tothe environmental behaviour of F-18 because of itsvery short radioactive half-life.

F





Terrestrial

Direct discharges of F-18 to theterrestrial environment wouldnot be expected to occur.

Aquatic

Discharges to sewers couldoccur. However, the F-18 woulddecay almost completely duringits transport through the sewersystem.

Atmospheric

F-18 could be released toatmosphere at the time of itsproduction.

With a half-life of 110 minutes,it could be dispersed downwindover a distance of up to about30 km.

Environmental sink

Because of its very shortradioactive half-life, the primaryenvironmental sink for F-18 isradioactive decay.


Fluorine is not highly accumulated by plants from soils.

Although some uptake could occur, the very short half-life of F-18means that external plant contamination from atmosphericdeposition or submersion in the plume is likely to be of greatestinterest.

For animals, inhalation is likely to be the main route.

Fluorine is rapidly absorbed from both the respiratory andgastrointestinal tracts, and is then rapidly and efficiently deposited incalcified tissues


F-18 is a beta-gamma emitter.

External gamma irradiation is likely to be ofgreatest significance, although the very short half-life of F-18 will limit the total dose.


No major species-specific considerations

F


Name


Parent

Iron-59

44.5 days

N/A

Symbol

Principal decaymode

Daughter

Fe-59

Beta [gamma]

Co-59

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes



Uses • Investigations of iron metabolism in the spleen

Modes Land • Sewage sludge application to land



Speciation

Iron is a transition metal that shows a number ofoxidation states, of which +2 and +3 are the mostimportant.

Of these, the +2 state is the most stable.

Iron forms a number of simple (e.g. sulphate,nitrate) and organometallic compounds.

Analogue species

Because Fe is an essential element for a widevariety of biota, it is most appropriately consideredin its own right rather than as an analogue ofother transition metals.

F





Terrestrial

Because of the short radioactivehalf-life of Fe-59, deposition onplants will be of much greaterimportance than uptake fromsoil.

As Fe is highly particle reactive,the bulk movement of soils willbe the main transportmechanism

Aquatic

Because Fe-59 is highly particlereactive, it will adsorb stronglyto suspended sediments andmigrate to bottom sediments bydeposition of particles.

Atmospheric

If Fe-59 is released to theatmosphere, it is likely to be asan aerosol.

Environmental sink

In the terrestrial environment,Fe-59 will decay mainly close toits site of deposition.

In the aquatic environment, Fe-59 will either decay in the watercolumn or in depositedsediment.


In the terrestrial environment, Fe-59 will mainly be present on theexternal surfaces of plants. Contamination on plants may be ingestedby animals.

Bioavailability of Fe-59 to animals depends both on chemical formand iron concentration. Fractional gastrointestinal absorption istypically ~10 %.

In mammals and birds, uptake from the gastrointestinal tract willresult in accumulation in the liver, spleen and other soft tissues.

Concentration ratios in freshwater and marine organisms relative towater range from a few hundred to more than 10,000 and there areno strong distinctions between types.


Fe-59 emits two gamma rays with high yield andenergies above 1 MeV.

Therefore, external irradiation from a dispersingplume and from ground deposits can be ofimportance.

Uptake in plants is of little significance fordosimetric purposes, but uptake and retention inlarger animals could result in a substantialcontribution from internal dose.


Special consideration should be given tofreshwater fish due to the high concentrationratios that can arise.

F


Name


Parent

Gallium-67

3.3 days

N/A

Symbol

Principal decaymode

Daughter

Ga-67

EC

Zn-67

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production • Generally produced in a cyclotron

Uses • In medical diagnostics for imaging tumours and lesions

Modes Land• Sewage sludge application to land, but would probably decay substantially before

this can occurof

Air • Not generally released to airrelease

Water • Hospital releases to sewers

Speciation

Gallium is a Group III element whose predominantoxidation state is +3.

Some compounds with an oxidation state of +1are known, but these are relatively unstable.

Gallium forms compounds with the halides,oxygen and sulphur.

Analogue species

The are no obvious analogues for theenvironmental behaviour of Ga.

G





Terrestrial

Because of its short radioactivehalf-life, deposition on plantswill be of much greaterimportance than uptake fromsoil.

Ga-67 would be expected to bepresent as externalcontamination of plant surfaces.

Aquatic

Little is known of the dispersionof Ga-67 in aquaticenvironments.

Atmospheric

If Ga-67 is released toatmosphere, it is likely to be asan aerosol.

Environmental sink

The short half-life of Ga-67means that it will decay interrestrial environments close toits point of deposition.

It is unlikely to disperse overlong distances in aquaticenvironments before it decays.


Little biotic transfer of Ga-67 is likely.

Ga-67 would be expected to be present as external contamination ofplant surfaces and not subject to significant gastrointestinalabsorption.


Ga-67 mainly emits moderately low energygamma emissions.

However, in view of its low bioavailability, externalirradiation may be the main route of exposure ofbiota.


As biotic availability is thought to be low, there areno major species-specific considerations.

G


Name


Parent

Tritium

12.4 years

N/A

Symbol

Principal decaymode

Daughter

H-3

Beta

He-3

Origin

Grouping

Detection

Cosmogenic

Natural

Laboratory


Decay modes


Production• Through cosmic ray interactions in the upper atmosphere• Neutron irradiation of lithium-6• As a fission product in nuclear reactors

Uses• As a tracer in biological and environmental studies• As a component in nuclear weapons• As an agent in luminous paints for various applications

ModesLand • Deposition from fallout from weapons tests or a nuclear accident

ofAir • Fallout from weapons tests or a nuclear accident

releaseWater • Natural atmospheric processes

• Liquid discharges from nuclear facilities

Speciation

Hydrogen occurs freely in nature as H2, butcombines with most elements to form hydrides.

Hydrogen is a major component of most organicmolecules and thus tritium can exchange withhydrogen-1 and become bound to suchmolecules.

In the environment, water is by far the mostimportant hydrogen-containing compound.

Analogue species

There is no appropriate analogue for H, nor is oneneeded, as the environmental behaviour of variousforms of H has been extensively studied.

H





Terrestrial

H-3 disperses in the terrestrialenvironment in flows of surfaceand ground waters.

Some conversion from tritiatedwater to OBT (organicallybound tritium) occurs in plants.

Aquatic

Cosmogenically produced H-3mixes with surface water bodiesthroughout the world.

In general, H-3 is highlyconservative and is rapidlydispersed.

Aquatic organisms canaccumulate H-3 either astritiated water, or followingconversion in the environmentasOBT.

Atmospheric

H-3 can be dispersed in theatmosphere as water vapour,elemental hydrogen or as acomponent of other gases, suchas methane.

It is ubiquitously present inwater vapour from cosmogenicproduction.

Environmental sink

Ocean waters are the main sinkfor H-3.

These waters exchange H-3with the atmosphere, so theenvironmental sink is bestconsidered as the two together.


H-3 is readily taken up by plants.

Some conversion from tritiated water to OBT occurs in plants.

In animals, uptake and retention is mainly of tritiated water, forexample from plants and drinking water.

Aquatic organisms take up H-3 by exchange from the surroundingwater and through the food chain.


H-3 is a soft beta emitter and is generally relativelyuniformly distributed throughout all body tissues.

Thus, doses to individual tissues are generally ofsimilar magnitude to average whole-body doses.


As H-3 is ubiquitously present in water in nearly allbiota, there are no major species-specificconsiderations.

H


Name


Parent

Iodine-123

13.2 hours

N/A

Symbol

Principal decaymode

Daughter

I-123

EC

Te-123 [R]

Origin

Grouping

Detection

Fission

Artificial

In situ


Decay modes



Uses • Biochemical analyses in the biological and life sciences

ModesLand • Sewage sludge application to land, but would probably decay away before this can occur

of Air• Not generally released to air, but some releases of volatile iodine compounds may

occur from sewage sludgerelease


Speciation

Iodine is a halogen element that exhibits anumber of stable oxidation states.

Two of the most important of these are the -1(iodide) and +5 (iodate) compounds.

Iodine can also take part in the formation oforganic complexes.

Analogue species

There are chemical similarities between F, Cl, Brand I.

However, I is an essential trace element that hasspecific biochemical roles and it has beenextensively studied.

Therefore, there is no need to rely on analogues tocharacterise its environmental behaviour.

I





Terrestrial

I-123 has a very short half-life.Following deposition, it willmainly be present on theexternal surfaces of plants.

As iodine is not particularlyparticle reactive, I-123 willmigrate in surface orgroundwaters through theterrestrial environment.

Aquatic

Because iodine is notparticularly particle reactive, itwill disperse freely in aquaticsystems, although some bindingto sediments can be expected.

Atmospheric

Iodine released to theatmosphere may disperse as avapour of the element, as anaerosol or as methyl iodide.

Elemental iodine and aerosolparticles are efficiently depositedto surfaces; this is not the casefor methyl iodide.

Environmental sink

The very short half-life of I-123means that it mainly decays asit disperses through theenvironment.

Iodine only exhibits a limiteddegree of sorption to mineralsolids, but it can have a highaffinity for organic matter.


I-123 will mainly be present on the external surfaces of plants, withsome translocation to inner plant parts.

It is highly bioavailable, being completely absorbed from thegastrointestinal tract of mammals and birds.

Although very short-lived, its half-life is long enough for it to betranslocated to the thyroid.

Iodine is only concentrated to a limited degree in most freshwaterand marine organisms, with the exception of marine plants (e.g.some algae and seaweeds).


I-123 emits mainly relatively low energy gammarays.

Because of its high degree of concentration in thethyroids of mammals and birds, radiation dose tothe thyroid is of primary interest, although gammadoses to other organs may be significant.

At lower doses, thyroid cancer would be the effectof particular interest but, at very high doses,hypothyroidism might occur.


No major species-specific considerations, althoughit should be noted that uptake to the thyroid isstrongly determined by the level of stable iodinepresent in the diet.

I


Name


Parent

Iodine-125

59.4 days

N/A

Symbol

Principal decaymode

Daughter

I-125

EC

Te-125

Origin

Grouping

Detection

Fission

Artificial

Laboratory


Decay modes


Production • Irradiation of stable nuclides in a reactor or cyclotron

Uses• Treatment of thyroid cancer• Biochemical analyses in medicine and the life sciences

Modes Land • Release from hospitals or research facilities

of Air • Release from hospitals or research facilities


Speciation




Analogue species




I





Terrestrial

Following deposition, I-125 willmainly be present on theexternal surfaces of plants.

As iodine is not particularlyparticle reactive, I-125 presentin soils will tend to migrate insurface or groundwatersthrough the terrestrialenvironment.

Aquatic


Atmospheric


Whereas elemental iodine andaerosol particles are efficientlydeposited to surfaces, this is notthe case for methyl iodide.

Environmental sink

I-125 mainly decays as itdisperses through theenvironment.





I-125 entering the systemic circulation of mammals and birds istranslocated to the thyroid.



I-125 emits low energy photons and Augerelectrons (see Glossary).

Because of its high degree of concentration in thethyroids of mammals and birds, radiation dose tothe thyroid is of primary interest.




I


Name


Parent

Iodine-129

1.57 x 107 years

N/A

Symbol

Principal decaymode

Daughter

I-129

Beta

Xe-129

Origin

Grouping

Detection

Fission

Artificial

Laboratory


Decay modes




Modes Land• Deposition following historic atmospheric nuclear weapons tests• Release from nuclear facilities

ofAir

• Releases during historic nuclear weapons test• Release from nuclear facilities

releaseWater • Liquid discharges from nuclear facilities

Speciation




Analogue species




I





Terrestrial



Aquatic


Atmospheric



Environmental sink

I-129 becomes widely dispersedin the worldís oceans.

In the very long term, theremay be some translocation ofthis I-129 to organic-richbottom sediments.



It is highly bioavailable, being completely absorbed from thegastrointestinal tract of mammals and birds, following ingestion ofcontaminated foodstuffs and drinking water.

I-129 entering the systemic circulation of mammals and birds istranslocated to the thyroid.



I-129 emits beta particles, low gamma rays andAuger electrons (see Glossary).


Because of its very low specific activity, there is nopossibility of delivering high doses to the thyroid,so the potential induction of thyroid cancer is theonly effect that could be of interest.



I


Name


Parent

Iodine-131

8.02 days

N/A

Symbol

Principal decaymode

Daughter

I-131

Beta [gamma]

Xe-131

Origin

Grouping

Detection

Fission

Artificial

In situ


Decay modes



Uses• Treatment of thyroid and (sometimes) bone cancer• Biochemical analyses in medicine and the life sciences

Modes Land• Deposition following a nuclear accident• Release from hospitals or nuclear facilities

ofAir • Released to air following a nuclear accident

releaseWater • Leaching from surface soils to groundwaters

Speciation




Analogue species




I





Terrestrial



Aquatic


Atmospheric



Environmental sink

I-131 mainly decays as itdisperses through theenvironment.





Although short-lived, its half-life is long enough for it to betranslocated to the thyroid.



I-131emits both beta particles and gamma rays.





I


Name


Parent

Indium-111

2.8 days

N/A

Symbol

Principal decaymode

Daughter

In-111

EC

Cd-111

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production • Produced during fission in a nuclear reactor• Neutron activation of non-radioactive precursors in a cyclotron or nuclear reactor

Uses • In medical diagnostics as a tool for studying the brain

Modes Land• Sewage sludge application to land, but would probably decay substantially before

this can occurof



Speciation

Indium is a Group III element that can showoxidation states of +1 and +3.

It forms ionic compounds with the halides (e.g.InF3) and also forms an oxide.

Indium dissolves in acids and is oxidised onheating in air.

Analogue species

No useful analogues for indium have beenidentified.

I





Terrestrial

Little is known of theenvironmental behaviour ofindium. However, it is not anessential trace element. With itsshort half-life, In-111 is likely tobe retained on the externalsurfaces of plants.

Aquatic

No information is readilyavailable on the behaviour ofindium in aquatic environments.

Atmospheric

If In-111 is released to theatmosphere, it is likely to be asan aerosol.

Environmental sink

In terrestrial environments,In-111 is likely to decay close toits site of deposition.

In aquatic environments, it willdecay either in the watercolumn or after deposition inbottom sediments.


There will be little uptake of In-111 by plants.

Animals may ingest externally contaminated plants and soils.However, only limited uptake of In-111 is likely to occur (thefractional gastrointestinal absorption in rats is about 2 %).

In-111 entering the systemic circulation is deposited mainly in bonemarrow, liver kidneys and spleen.


In-111 emits mainly gamma rays.

In view of its short half-life and low bioavailability,external irradiation is likely to be of greaterimportance than internal exposure of terrestrialplants and animals.


No species-specific considerations have beenidentified.

I


Name


Parent

Indium-113m

1.7 hours

N/A

Symbol

Principal decaymode

Daughter

In-113m

IT

In-113

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production • Irradiation of stable precursors with neutrons in a nuclear reactor or cyclotron

Uses• Diagnostic imaging of various parts of the body (liver, spleen, brain)• Determination of blood volume and cardiac output




Speciation

Indium is a group III element that can showoxidation states of +1 and +3.

It forms ionic compounds with the halides (e.g.InF3) and also forms an oxide.

Indium dissolves in acids and is oxidised onheating in air.

Analogue species

No useful analogues for indium have beenidentified.

I





Terrestrial

Little is known of theenvironmental behaviour ofindium. However, it is not anessential trace element.

Aquatic


Atmospheric

If In-113m is released to theatmosphere, it is likely to be asan aerosol.

Environmental sink

In terrestrial environments, In-113m is likely to decay closeto its site of deposition.



There will be little uptake of In-113m by plants.

Animals may ingest externally contaminated plants and soils.However, only limited uptake of In-113m is likely to occur (thefractional gastrointestinal absorption in rats is ~2 %).

In-113m entering the systemic circulation is deposited mainly inbone marrow, liver kidneys and spleen.


In-113m emits gamma rays of energy 0.39 MeV.

In view of its very short half-life and lowbioavailability, external irradiation is likely to be ofgreater importance than internal exposure ofterrestrial plants and animals.



I


Name


Parent

Potassium-40

1.3 x 109 years

N/A

Symbol

Principal decaymode

Daughter

K-40

Beta

Ca-40

Origin

Grouping

Detection

Primordial

Natural

In situ


Decay modes


Production • Naturally during the formation of the universe

Uses • No specific uses outside research activities

Modes Land • Present in all soils and rocks


release Water • Leaching via infiltration through to groundwater

Speciation

Potassium is an alkali metal whose chemicalbehaviour is determined by the properties of theK+ ion.

Most of the compounds of potassium are ionic innature, although more complex species can beformed.

Potassium reacts extremely vigorously with water,oxygen and halogens.

Analogue species

K is a chemical analogue of Cs.

However, as K is an essential element for all biota,except possibly a few bacteria, it is moreappropriate to consider Cs by analogy with K thanvice versa.

K





Terrestrial

Little is known of theenvironmental behaviour ofindium. However, it is not anessential trace element.

Aquatic


Atmospheric

If In-113m is released to theatmosphere, it is likely to be asan aerosol.

Environmental sink

In terrestrial environments, In-113m is likely to decay closeto its site of deposition.



There will be little uptake of In-113m by plants.

Animals may ingest externally contaminated plants and soils.However, only limited uptake of In-113m is likely to occur (thefractional gastrointestinal absorption in rats is ~2 %).

In-113m entering the systemic circulation is deposited mainly inbone marrow, liver kidneys and spleen.


In-113m emits gamma rays of energy 0.39 MeV.

In view of its very short half-life and lowbioavailability, external irradiation is likely to be ofgreater importance than internal exposure ofterrestrial plants and animals.



K


Name


Parent

Krypton-79

35 hours

N/A

Symbol

Principal decaymode

Daughter

Kr-79

EC

Br-79

Origin

Grouping

Detection

Activation

Artificial

Laboratory


Decay modes


Production • Neutron irradiation of stable precursors in a cyclotron or nuclear reactor

Uses • Sometimes used as a gaseous industrial radiotracer


of Air • Industrial applications could result in some releases to air


Speciation

Krypton is a noble gas and, as such, forms only alimited number of chemical compounds due to itslack of reactivity.

One such example is KrF2.

Analogue species



For this reason, Rn should not be used as ananalogue for Kr.

K





Terrestrial

Kr-79 is not transferredsignificantly to the terrestrialenvironment.

Aquatic

Kr-79 is not transferredsignificantly to the aquaticenvironment.

Atmospheric

Kr-79 is almost exclusivelyreleased to the atmosphere.

Its very short radioactive half-lifeand low reactivity means that itdecays almost entirely duringatmospheric transport and is nottransferred significantly to otherenvironmental media.

Environmental sink

No major sink owing to its lackof reactivity and very short half-life.


Kr-79 is sparingly soluble in body tissues, notably those with a highfat content. However, it is not metabolised.

Some Kr-79 will be present in the lungs in inhaled air.


Kr-79 emits mainly gamma rays, either directly oras positron-annihilation radiation.

Radiation doses arise from:

• external beta irradiation of superficial tissues ofboth plants and animals;

• irradiation of the lungs of animals fromcontained gas and internal irradiation from gasdissolved in tissues.



However, aquatic organisms, plant roots andburrowing animals will be shielded, to a greater orlesser degree, from such exposures.

K


Name


Parent

Krypton-81

2.1 x 105 years

N/A

Symbol

Principal decaymode

Daughter

Kr-81

EC

Br-81

Origin

Grouping

Detection

Cosmogenic

Natural

Laboratory


Decay modes


Production • From the decay of cyclotron-manufactured rubidium-81• From the action of cosmic rays in the upper atmosphere

Uses • The metastable species krypton-81m is used for lung ventilation scintigraphy


of Air • Hospital applications could result in some releases to air


Speciation

Krypton is a noble gas and lacks reactivity; assuch, it forms only a limited number of chemicalcompounds.


Analogue species




K





Terrestrial


Aquatic


Atmospheric

Kr-81 is almost exclusivelyreleased to, or generated in, theatmosphere.

Its low reactivity means that itdecays almost entirely in theatmosphere and is nottransferred significantly to otherenvironmental media.

Environmental sink

No major sink owing to its lackof reactivity.





Kr-81 is a weak gamma emitter. Exposures aremainly by external irradiation.

Cosmogenic Kr-81 gives rise to negligible doserates to organisms compared with othercosmogenic radionuclides such as C-14.

Radiation doses arise from irradiation of the lungsof animals from contained gas and internalirradiation from gas dissolved in tissues.


As Kr-81 is globally dispersed in the atmosphereand is not accumulated in any environmentalmedia, there are no major species-dependentconsiderations.


K


Name


Parent

Krypton-85

10.7 years

N/A

Symbol

Principal decaymode

Daughter

Kr-85

Beta

Rb-85

Origin

Grouping

Detection

Fission

Artificial

Laboratory


Decay modes





of Air • From fission reactors and reprocessing facilities


Speciation

Krypton is a noble gas and, as such, forms only alimited number of chemical compounds due to itslack of reactivity.


Analogue species




K





Terrestrial


Aquatic


Atmospheric

Kr-85 is almost exclusivelyreleased to the atmosphere.

Its low reactivity means that itdecays almost entirely in theatmosphere and is nottransferred significantly to otherenvironmental media.

Environmental sink

No major sink owing to its lackof reactivity.





Kr-85 is mainly a beta emitter, with a smallcomponent of gamma emission.

Radiation doses arise from:

• external beta irradiation of superficial tissues ofboth plants and animals;

• irradiation of the lungs of animals fromcontained gas and internal irradiation from gasdissolved in tissues.


Because Kr-85 is not metabolised to any significantdegree, there are no major species-dependentconsiderations.

K


Name


Parent

Lanthanum-140

1.7 days

N/A

Symbol

Principal decaymode

Daughter

La-140

Beta [gamma]

Ce-140

Origin

Grouping

Detection

Fission

Artificial

In situ


Decay modes



Uses• Used in blast furnaces to measure residence times and to quantify furnace

performance

Modes Land • Could be released to land following the disposal of ashes from furnaces

of Air • Could enter the atmosphere in gaseous furnace wastes during burning


Speciation

Lanthanum is a rare earth element that shows anoxidation state of +3.

As such, lanthanum forms compounds withhydrogen, oxygen and the halides. It also formsstable complexes.

Analogue species


Analogies with other members and higheractinides such as Am can be useful.

L





Terrestrial

La-140 is highly particlereactive, and hence wouldremain bound to soil particlesand on the surfaces of plants.


Aquatic

La-140 is highly particlereactive. It is likely to bind tosuspended sediments andwould migrate from the watercolumn to bottom sediments bydeposition.

Atmospheric

If La-140 was released to theatmosphere, it would be as anaerosol.

Environmental sink

The very short half-life and highparticle reactivity of La-140mean that it is likely to decayclose to its site of deposition interrestrial environments.



Intake by terrestrial animals is likely to be mainly the ingestion of La-140 present on the exterior surfaces of plants or deposited on soil.

La-140 is not very bioavailable to animals. The fractionalgastrointestinal absorption is typically <0.1 %. Any La-140 that isabsorbed is mainly deposited in the liver and skeleton.




La-140 emits energetic gamma photons.

Because of its low bioavailability and very shorthalf-life, external irradiation is more likely to beimportant than internal exposure.


In mammals and birds, the walls of thegastrointestinal tract are likely to receivesubstantially higher doses than other organs andtissues.

L


Name


Parent

Manganese-54

313 days

N/A

Symbol

Principal decaymode

Daughter

Mn-54

EC

Cr-54

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production• Produced by irradiating stable isotopes with neutrons or protons in a nuclear

reactor or cyclotron

Uses• Used to predict the behaviour of heavy metal components in effluents from

mining waste water


of Air • Could enter groundwater following mining water experiments

release Water • Not generally released to air

Speciation

Manganese is a transition element of Group VIIthat can show a wide range of oxidation states.

Oxidation states +2 and +3 show the widest rangeof compounds.

Manganese forms a range of oxides, includinglower oxides (e.g. MnO) and higher oxides(manganates, e.g. MnO4

-)

Analogue species

Although Mn has some chemical, biochemical andbiogeochemical affinities with Cr, Fe and Tc, itshigh concentrations in the environment and itsimportance as an essential trace element meanthat it is not appropriate to consider it as ananalogue of any other element.

M





Terrestrial

Mn-54 is moderately particlereactive in soils and sediments.

It also tends to react withorganic matter.

Mn distributes relativelyuniformly throughout planttissues.

Aquatic

Mn-54 is highly particle reactivein aquatic environments.

It will rapidly associate withsuspended sediments.

Atmospheric

If Mn-54 was released toatmosphere, it would be as anaerosol.

MnO2 is the most likely form.

Environmental sink

As Mn-54 has a half-life of only313 days and is moderatelyparticle reactive, it can beexpected to be retained interrestrial soils and sediments,and to decay in situ.

In the aquatic environment,Mn-54 will decay in bottomsediments close to its point ofdeposition.


Mn distributes relatively uniformly throughout plant tissues.

Plant concentrations are similar to soil concentrations on a dry massbasis.

Mn is moderately bioavailable to animals, with a fractionalgastrointestinal absorption of ~5 %. However, it is well retained inthe body, concentrating in the liver and bone.

Very high concentration ratios relative to water are observed in allclasses of marine organisms, ranging up to 10,000 or more.

Concentration ratios in freshwater fish are rather lower, ranging upto about 500.


The main emission from Mn-54 is an energeticgamma ray.

Plants will be irradiated relatively uniformly fromexternal and internal deposits of Mn-54.

In animals, the long range of the emitted photonand significant uptake in other tissues means thatmost organs and tissues receive similar radiationdoses.



M


Name


Parent

Manganese-56

2.6 hours

N/A

Symbol

Principal decaymode

Daughter

Mn-56

Beta [gamma]

Fe-56

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production • Neutron activation of stable manganese present in reactor structures

Uses • Occasionally as a radiotracer




Speciation

Manganese is a transition element of Group VIIthat can show a wide range of oxidation states.

Oxidation states +2 and +3 show the widest rangeof compounds.

Manganese forms a range of oxides, includinglower oxides (e.g. MnO) and higher oxides(manganates, e.g. MnO4

-)

Analogue species

Although Mn has some chemical, biochemical andbiogeochemical affinities with Cr, Fe and Tc, itshigh concentrations in the environment and itsimportance as an essential trace element meanthat it is not appropriate to consider it as ananalogue of any other element.

M





Terrestrial

Mn-56 is moderately particlereactive in soils and sediments.

It also tends to react withorganic matter.

Mn distributes relativelyuniformly throughout planttissues.

Aquatic

Mn-56 is highly particle reactivein aquatic environments.


Atmospheric

If Mn-56 was released toatmosphere, it would be as anaerosol.

MnO2 is the most likely form.

Environmental sink

Mn-56 deposited in theterrestrial environment wouldbe expected to decay close toits point of deposition.

Mn-56 in aquatic dischargeswould decay during transit tothe surface water environmentor shortly after discharge, eitherin the water column or indeposited sediments.


The very short half-life of Mn-56 means that it has little opportunityfor uptake by either plants or animals.


Mn-56 is a beta-gamma emitter.

The main consideration with Mn-56 in theterrestrial environment is external irradiation.

In the aquatic environment, high external doserates could occur due to trapping in depositedsediments close to the point of discharge.


No species-specific considerations, as the shorthalf-life of Mn-56 means that there will be littleopportunity for organisms to accumulate theradionuclide.

M


Name


Parent

Molybdenum-99

66 hours

N/A

Symbol

Principal decaymode

Daughter

Mo-99

Beta

Tc-99m [R],Tc-99 [R]

Origin

Grouping

Detection

Fission

Artificial

In situ


Decay modes


Production • During the fission process in a nuclear reactor

Uses • To produce technetium-99 for medical applications

Modes Land• During treatment and disposal of spent fuel• Sewage sludge application to land, but would probably decay away before

this can occur

ofAir

• Not generally released to air - some possible during treatment and disposalof spent fuel

releaseWater

• Not generally released to water - some possible during treatment and disposalof spent fuel

• Hospital releases to sewers

Speciation

Molybdenum is a transition metal that shows alloxidation states from -2 through to +6.

Molybdenum forms compounds with thehalogens, oxygen and sulphur.

It readily forms complexes with a wide range ofatoms, most notably oxygen and sulphur.

Analogue species

Molybdenum is an essential trace element.

It exhibits distinctive chemical and biochemicalbehaviour and it is inappropriate to identify ananalogue.

M





Terrestrial

Mo-99 is moderately particlereactive. Some transfer throughthe terrestrial environment canbe expected in surface andgroundwaters, but much willremain in situ.

Mo-99 deposited on plants willbe subject to a limited degree offoliar absorption.

Aquatic

Molybdenum in freshwaters ismainly present as dissolvedspecies.

In seawater, both dissolved andadsorbed Mo-99 could bepresent in similar quantities.

In acid waters, Mo-99 mayattach to colloidal particles ofiron hydroxides.

Atmospheric

If Mo-99 is released toatmosphere, it is likely to be as aliquid or solid aerosol.

Environmental sink

In the terrestrial environment,Mo-99 will decay close to itspoint of deposition.

In the aquatic environment, itwill decay in the water column.


Although foliar absorption is thought to occur readily, the short half-life of Mo-99 will limit the degree to which it takes place.

Mo-99 is highly available to animals, with a fractional gastrointestinalabsorption of ~80 %.

Although there is some preferential uptake in the skeleton, most Mo-99 will be relatively uniformly distributed throughout soft tissues.

Concentration ratios for Mo relative to water are 10-100 in marineplants, around 1,000 in freshwater plants, from 1 to 100 in marinemolluscs and around 10 in marine and freshwater fish.


Mo-99 will be present with Tc-99m in theenvironment.

Beta and gamma emissions from these tworadionuclides will generally give rise to relativelyuniform internal whole-body exposures of all typesof biota.

External exposures from deposited Mo-99 andassociated Tc-99m may also be of somesignificance in the terrestrial environment.


Tc-99m produced from Mo-99 decaying in thebodies of mammals and birds may have atendency to translocate to the thyroid, followingpathways of iodine metabolism.

However, its short half-life and the inability of thethyroid to utilise it for hormone production willlimit the significance of this pathway.

M


Name


Parent

Sodium-22

2.6 years

N/A

Symbol

Principal decaymode

Daughter

Na-22

Beta [gamma]

Ne-22

Origin

Grouping

Detection

Cosmogenic

Natural

In situ


Decay modes



Uses • In medicine as a radiotracer and for diagnostic purposes




Speciation

Sodium is an alkali metal whose chemicalbehaviour is determined by the properties of theNa+ ion.

Most of the compounds of sodium are ionic innature, although more complex species can beformed.

Sodium reacts extremely vigorously with water,oxygen and halogens.

Analogue species

Na is an essential element for animals, but is lessimportant for plants.

Its chemistry, biochemistry and biogeochemistryare distinct from those of the other alkali metals(e.g. K) and it is inappropriate to consider it byanalogy.

N





Terrestrial

Sodium is moderately particlereactive.

Therefore, it can be expected toremain largely in situ, althoughsome dispersion through theterrestrial environment willoccur.

Aquatic

The dominant form of sodiumin waters is Na+, but a limiteddegree of sorption to suspendedsediments may occur.

Nevertheless, Na-22 would beexpected to behaveconservatively in aquaticsystems.

Atmospheric

If Na-22 was released to theatmosphere, it would be in theform of an aerosol.

Environmental sink

Na-22 will migrate to someextent in the soil column andfrom terrestrial deposits tosurface water bodies beforedecaying.

However, the degree ofmovement will differsubstantially in Na-rich and Na-deficient soils.

In aquatic systems, Na-22 willdecay mainly in the watercolumn.


In terrestrial environments, high concentrations will occur in plantsfrom active uptake.

High concentrations may also occur in animals following ingestion ofcontaminated plant material or drinking water.

Gastrointestinal absorption is virtually complete.

Concentrations of Na-22 in plants and animals will tend to be higherin Na-deficient than in Na-rich conditions.

A relatively high degree of uptake is expected in freshwaterorganisms, but not in marine organisms.


Na-22 is a positron emitter. Thus, it emitsannihilation gamma rays of energy 0.511 MeV, aswell as a gamma ray of energy 1.275 MeV.

These gamma rays mean that Na-22 can give riseto significant external exposure.

However, its high bioavailability in terrestrial andfreshwater environments means that internalexposures are likely to be more important.


Terrestrial plants and animals living in Na-deficientconditions need to be given special consideration.

Freshwater organisms in environments in whichthe Na-22 is not rapidly dispersed and dilutedshould also be given special consideration.

N


Name


Parent

Sodium-24

15 hours

N/A

Symbol

Principal decaymode

Daughter

Na-24

Beta [gamma]

Mg-24

Origin

Grouping

Detection

Cosmogenic

Natural

In situ


Decay modes



Uses • In medicine as a radiotracer and for diagnostic purposes




Speciation

Sodium is an alkali metal whose chemicalbehaviour is determined by the properties of theNa+ ion.

Most of the compounds of sodium are ionic innature, although more complex species can beformed.

Sodium reacts extremely vigorously with water,oxygen and halogens.

Analogue species



N





Terrestrial

Sodium is moderately particlereactive.

Therefore, it can be expected toremain largely in situ, althoughsome dispersion through theterrestrial environment willoccur.

Aquatic

The dominant form of sodiumin waters is Na+, but a limiteddegree of sorption to suspendedsediments may occur.

Nevertheless, Na-24 would beexpected to behaveconservatively in aquaticsystems.

Atmospheric

If Na-24 was released to theatmosphere, it would be in theform of an aerosol.

Environmental sink

Na-24 will migrate to someextent in the soil column andfrom terrestrial deposits tosurface water bodies beforedecaying.

However, the very short half-lifeof Na-24 will limit the degree ofmigration.

In aquatic systems, Na-24 willdecay mainly in the watercolumn.


In terrestrial environments, high concentrations will occur in plantsfrom active uptake.

High concentrations may also occur in animals following ingestion ofcontaminated plant material or drinking water.

Gastrointestinal absorption is virtually complete.

Concentrations of Na-24 in plants and animals will tend to be higherin Na-deficient than in Na-rich conditions.

A relatively high degree of uptake is expected in freshwaterorganisms, but not in marine organisms.


Na-24 emits a beta particle and gamma rays withenergies of 1.37 and 2.75 MeV.

These gamma rays mean that Na-24 can give riseto significant external exposure.

Because of its very short half-life, externalexposure may be of more significance thaninternal exposure.

However, the high bioavailability of Na-24 meansthat internal exposures must not be neglected.


Terrestrial plants and animals living in Na-deficientconditions need to be given special consideration.

Freshwater organisms in environments in whichthe Na-24 is not rapidly dispersed and dilutedshould also be given special consideration.

N


Name


Parent

Niobium-94

2.03 x 104 years

N/A

Symbol

Principal decaymode

Daughter

Nb-94

Beta [gamma]

Mo-94

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production • Neutron irradiation of niobium-93 present in reactor components

Uses • As a laboratory source of gamma rays




Speciation

The chemistry of niobium is dominated by the +5oxidation state.

It forms halide compounds that hydrolyse easily toform niobium oxide, Nb2O5.

The niobate ion (NbO3-) can also be formed by

reducing niobium oxide.

Niobium can also take part in the formation ofcolloids and organic complexes.

Analogue species



N





Terrestrial

Nb-94 is moderately particlereactive in terrestrial soils. It isstrongly excluded from plants.

The little Nb-94 that is taken upby roots is mainly retained thereand not translocated to aboveground tissues.

Aquatic

Nb-94 is highly particle reactivein aquatic sediments.


Atmospheric

If Nb-94 is released toatmosphere, it is likely to be asan aerosol.

Environmental sink

In terrestrial environments, Nb-94 will mainly be retained inthe soil column.

In aquatic environments, mostNb-94 is likely to becomeadsorbed to suspendedsediments and hence migrate tobottom sediments.


Nb-94 is not very bioavailable to plants.

Animal intakes are likely to result mainly from the ingestion of soil orof contaminated drinking water.

The fractional gastrointestinal absorption is ~0.2 %, except in pre-weaned animals. Much of the uptake is deposited in mineral bone,with the remainder widely dispersed amongst soft tissues.

Concentration ratios relative to water are ~30 for freshwater andmarine fish. Concentration ratios for marine molluscs and crustaceansare typically ~200 and ~1,000, respectively. Concentration ratios formarine plants are also ~1,000.


Nb-94 is a beta-gamma emitter.

External exposure is likely to be of greaterimportance than internal exposure in manycontexts, notably in the terrestrial environment.


Special consideration should be given to marinemolluscs, crustaceans and plants in view of theconcentration ratios for these species.

N


Name


Parent

Niobium-95

35 days

Zr-95

Symbol

Principal decaymode

Daughter

Nb-95

Beta [gamma]

Mo-95

Origin

Grouping

Detection

Radiogenic

Artificial

In situ


Decay modes


Production• Produced during fission in a nuclear reactor• From the decay of Zr-95, also an important fission product


ModesLand • During treatment and disposal of spent fuel

ofAir • Not generally released to air

release Water• During treatment and disposal of spent fuel• Liquid discharges from nuclear facilities

Speciation

The chemistry of niobium is dominated by the +5oxidation state.

It forms halide compounds that hydrolyse easily toform niobium oxide, Nb2O5.

The niobate ion (NbO3-) can also be formed by

reducing niobium oxide.

Niobium can also take part in the formation ofcolloids and organic complexes.

Analogue species

Zr and Nb have been quite extensively studied.

They exhibit considerable similarities in theirenvironmental behaviour.

N





Terrestrial

Nb-95 is moderately particlereactive in terrestrial soils. It isstrongly excluded from plants.

The little Nb-95 that is taken upby roots is mainly retained thereand not translocated to aboveground tissues.

Aquatic

Nb-95 is highly particle reactivein aquatic sediments.


Atmospheric

If Nb-95 is released toatmosphere, it is likely to be asan aerosol.

Environmental sink

In terrestrial environments, Nb-95 will mainly be retained inthe soil column.

In aquatic environments, mostNb-95 is likely to becomeadsorbed to suspendedsediments and hence migrate tobottom sediments.


Nb-95 is not very bioavailable to plants.

Animal intakes are likely to result mainly from the ingestion of soil orof contaminated drinking water.

The fractional gastrointestinal absorption is ~0.2 %, except in pre-weaned animals. Much of the uptake is deposited in mineral bone,with the remainder widely dispersed amongst soft tissues.

Concentration ratios relative to water are ~30 for freshwater andmarine fish. Concentration ratios for marine molluscs and crustaceansare typically ~200 and ~1,000, respectively. Concentration ratios formarine plants are also ~1,000.


Nb-95 is a beta-gamma emitter.

External exposure is likely to be of greaterimportance than internal exposure in manycontexts, notably in the terrestrial environment.


Because of its low bioavailability and theimportance of external irradiation, there are nomajor species-specific considerations.

However, special consideration should be given tobenthic aquatic organisms located close to sourcesof aquatic release, as these may be exposed tohigh Nb-95 concentrations in depositedsediments.

N


Name


Parent

Nickel-59

7.6 x 104 years

N/A

Symbol

Principal decaymode

Daughter

Ni-59

Beta

Co-59

Origin

Grouping

Detection

Cosmogenic

Natural

Laboratory


Decay modes


Production

• Fission neutron irradiation of metallic nuclear reactor components(e.g. Cr, Mn, Fe, Co, Ni)

• Cosmic ray interactions in the upper atmosphere


ModesLand • Treatment and disposal of spent fuel hardware

of Air• Treatment and disposal of spent fuel hardware• Trace amounts due to fallout from weapons testing

releaseWater • Treatment and disposal of spent fuel hardware

Speciation

Nickel is a transition metal that can exist in anumber of oxidation states.

The +2 state is the most stable in terms of theproperties of the compounds for variations in pHand Eh.

Such compounds include the halides, hydroxideand carbonate.

Analogue species

There are chemical, biochemical andbiogeochemical similarities amongst a number ofthe transition metals.

However, Ni is an essential trace element in somespecies and its environmental behaviour has beenextensively studied.

Therefore, it is not necessary or appropriate to relyon analogues.

N





Terrestrial

Ni is moderately particlereactive in soils and is unlikelyto be available for uptake byplants.

Aquatic

Ni is highly particle reactive inboth freshwaters and marineenvironments.

Significant migration todeposited sediments is likely tooccur in both types ofenvironment.

Atmospheric

If Ni-59 is released to theatmosphere, it is likely to be asan aerosol.

Environmental sink

Although Ni-59 will bemoderately well retained insoils, its long half-life meansthat there will eventually besignificant transfer to aquaticenvironments by leaching anderosive processes.

In the aquatic environment,most Ni-59 is likely toeventually be present indeposited sediments, which iswhere it will mainly decay.


Ni-59 is not particularly bioavailable to plants.

Intakes by animals in terrestrial environments will be of Ni-59incorporated in plants, bound to soil and in drinking water.

Ni is not very bioavailable to animals, with a fractionalgastrointestinal absorption of ~5 %.

That which is not rapidly excreted becomes uniformly distributed inthe body and tenaciously retained.

Concentration ratios relative to water are typically ~100 forfreshwater and marine fish, and ~1,000 for marine plants, molluscsand crustaceans.


Ni-59 emits low energy X-rays and electrons.

This means that external irradiation is of littleimportance.

Ni-59 incorporated into organisms is distributedrelatively uniformly throughout them. Doses toindividual organs and tissues will thus be of similarmagnitude to average whole-body doses.


No major species-specific considerations have beenidentified.

However, special consideration should be given tobenthic organisms located close to sources ofaquatic release, as these may be exposed to highNi-59 concentrations in aquatic sediments andtake up Ni-59 from those sediments.

N


Name


Parent

Nickel-63

100 years

N/A

Symbol

Principal decaymode

Daughter

Ni-63

Beta

Cu-63

Origin

Grouping

Detection

Activation

Artificial

Laboratory


Decay modes


Production• Fission neutron irradiation of metallic nuclear reactor components

(e.g. Cr, Mn, Fe, Co, Ni)


ModesLand • Treatment and disposal of spent fuel hardware

of Air• Treatment and disposal of spent fuel hardware• Trace amounts due to fallout from weapons testing

releaseWater • Treatment and disposal of spent fuel hardware

Speciation

Nickel is a transition metal that can exist in anumber of oxidation states.

The +2 state is the most stable in terms of theproperties of the compounds for variations in pHand Eh.

Such compounds include the halides, hydroxideand carbonate.

Analogue species

There are chemical, biochemical andbiogeochemical similarities amongst a number ofthe transition metals.

However, Ni is an essential trace element in somespecies and its environmental behaviour has beenextensively studied.

Therefore, it is not necessary or appropriate to relyon analogues.

N





Terrestrial

Ni is moderately particlereactive in soils and little addedNi-63 is likely to remainavailable for uptake by plants.

Aquatic

Ni is highly particle reactive inboth freshwaters and marineenvironments.

Significant migration todeposited sediments is likely tooccur in both types ofenvironment.

Atmospheric

If Ni-63 is released to theatmosphere, it is likely to be asan aerosol.

Environmental sink

Although Ni-63 will bemoderately well retained insoils, its long half-life meansthat there will eventually besignificant transfer to aquaticenvironments by leaching anderosive processes.

In the aquatic environment,most Ni-63 is likely toeventually be present indeposited sediments, which iswhere it will mainly decay.


Ni-63 is not particularly bioavailable to plants.

Intakes by animals in terrestrial environments will be of Ni-63incorporated in plants, bound to soil and in drinking water.

Ni is not very bioavailable to animals, with a fractionalgastrointestinal absorption of around 5 %.

That which is not rapidly excreted becomes uniformly distributed inthe body and tenaciously retained.

Concentration ratios relative to water are typically ~100 forfreshwater and marine fish, and ~1,000 for marine plants, molluscsand crustaceans.


Ni-63 emits low-energy beta particles.






N


Name


Parent

Neptunium-237

2.1 x 106 years

Am-241

Symbol

Principal decaymode

Daughter

Np-237

Alpha

Pa-233 [R]

Origin

Grouping

Detection

Breeding

Artificial

Laboratory


Decay modes


Production• Trace quantities found in nature• Decay of americium-241 produced in a nuclear reactor

Uses • Sometimes used in neutron detection equipment

Modes Land • Treatment and disposal of spent fuel


release Water • Treatment and disposal of spent fuel

Speciation

Neptunium can exist in a number of oxidationstates, but only the +4 and +5 states are importantin environmental systems.

A variety of species in aqueous solution can beformed, depending on Eh and pH.

Analogue species

There are chemical similarities between Np and U,and also between Np and Pu.

However, the chemistry, biochemistry andbiogeochemistry of Np are complex, and neither Unor Pu can be relied upon as quantitativeanalogues for its behaviour in the environment.

N





Terrestrial

Np-237 is moderately particlereactive in terrestrial soils andsediments.

Most Np-237 will thereforeremain in situ.

Aquatic

Np-237 is highly particlereactive in the aquaticenvironment and thereforetends to migrate to bottomsediments.

Atmospheric

Np-237 would be expected todisperse as an aerosol.

Environmental sink

Np-237 deposited in theterrestrial environment willmainly be transferred to soils,where it will tend to remain.

In aquatic systems, bottomsediments are the most likelyenvironmental sink and Np-237migration will be closelyassociated with sedimenttransport.


Np-237 is quite strongly excluded from plants. Much of the Np-237content of plants is likely to be due to surface contamination.

Ingestion of contaminated soil or sediment and inhalation couldcompete with ingestion of contaminated plant material as importantroutes of intake by animals.

Uptake from the gastrointestinal tract is limited (typically ~0.001),although enhanced concentrations of Np-237 may occur in the liver,kidneys and skeleton.

Concentration ratios of between 10 and 100 are typical for marineand freshwater species.


Ni-63 emits low-energy beta particles.






N


Name


Parent

Oxygen-15

122 seconds

N/A

Symbol

Principal decaymode

Daughter

O-15

Beta

N-15

Origin

Grouping

Detection

Activation

Artificial

Laboratory


Decay modes


Production • Produced by irradiating stable precursors in a cyclotron

Uses • Used in positron emission tomography to study brain physiology and pathology


of Air • Could be released to air, but the very short half-life mitigates any adverse impact


Speciation

The predominant oxidation state for oxygen is -2.

It is an extremely reactive gas and is capable offorming compounds with most other elements,usually forming one or more oxides of thoseelements.

Analogue species

Oxygen is a ubiquitous element in theenvironment and is involved in a wide variety ofbiological, biochemical and biogeochemicalprocesses.

There is no appropriate analogue, but theenvironmental behaviour of the stable element hasbeen extensively studied.

O





Terrestrial

The half-life of O-15 is too shortfor significant transport in theterrestrial environment to occur.

Aquatic

The half-life of O-15 is too shortfor significant transport in theaquatic environment to occur.

Atmospheric

O-15 has a radioactive half-lifeof only 122 seconds. Therefore,the only potentially relevantpathway is atmospheric releaseand exposure from thedispersing plume.

Dispersion distances before theactivity is substantially depletedby radioactive decay will be nomore than a few kilometres.

Environmental sink

O-15 released to theatmosphere will decay as itdisperses.


The main uptake mechanism for O-15 is inhalation, although any O-15 that is absorbed by organisms will decay rapidly.


The 0.511 MeV photons from O-15 will give riseto whole-body exposure from external irradiation.

Positron emissions can also give rise to superficialexposures to organisms, but this is likely to be asecondary consideration.




O


Name


Parent

Phosphorus-32

14.3 days

N/A

Symbol

Principal decaymode

Daughter

P-32

Beta

S-32

Origin

Grouping

Detection

Activation

Artificial

Laboratory


Decay modes


Production • Produced by irradiating stable precursors in a cyclotron

Uses • Used in positron emission tomography to study brain physiology and pathology


of Air • Could be released to air, but the very short half-life mitigates any adverse impact


Speciation

Phosphorus is a Group V element that shows twostable oxidation states, +3 and +5.

Phosphorus forms compounds with the halides,hydrogen, oxygen and sulphur, and forms a rangeof organic acids.

Phosphorus can be obtained in a number ofallotropic forms, of which white phosphorus is themost reactive.

Analogue species

Oxygen is a ubiquitous element in theenvironment and is involved in a wide variety ofbiological, biochemical and biogeochemicalprocesses.

There is no appropriate analogue, but theenvironmental behaviour of the stable element hasbeen extensively studied.

P





Terrestrial

Phosphorus shows only limitedparticle reactivity, and so can beexpected to move freelythrough the terrestrialenvironment, rather thanremaining in situ.

Aquatic

In aquatic ecosystems,phosphorus is present asparticulate organic phosphorus,dissolved inorganic phosphatesand dissolved organicphosphorus.

In most aquatic environments,particulate phosphorus is ingreatest abundance.

Atmospheric

If P-32 were released to theatmosphere, it would probablybe in the form of an aerosol.

Environmental sink

P-32 is sufficiently short-livedthat it will decay close to its siteof deposition in the terrestrialenvironment.

In the aquatic environment, P-32 is likely to decay mainly inthe water column, either insolution or incorporated inorganic particles.


P-32 deposited on land is likely to be highly available to plants, assoils typically contain only 0.65 ppm but plants contain about 1,000ppm.

It is highly available to animals, with gastrointestinal absorptionbeing almost complete.

In the short-term, phosphorus is widely distributed throughout alltissues. In the long-term, calcified tissues are the main reservoir.

In aquatic environments, very rapid uptake by organisms can beexpected, leading to concentration ratios relative to water of 10,000or more.


P-32 is a pure beta emitter.

Because of this and its high bioavailability, internalexposures will be of principal importance.

Although there may be some degree ofpreferential irradiation of calcified tissues, theeffect will be limited by the short half-life of theradionuclide.



P


Name


Parent

Phosphorus-33

25.3 days

N/A

Symbol

Principal decaymode

Daughter

P-33

Beta

S-33

Origin

Grouping

Detection

Activation

Natural

Laboratory


Decay modes


Production • Neutron bombardment of stable sulphur-33 in a cyclotron

Uses • In medicine as a radiotracer




Speciation

Phosphorus is a Group V element that shows twostable oxidation states, +3 and +5.

Phosphorus forms compounds with the halides,hydrogen, oxygen and sulphur, and forms a rangeof organic acids.

Phosphorus can be obtained in a number ofallotropic forms, of which white phosphorus is themost reactive.

Analogue species

Phosphorus as phosphate is essential to all livingcells and is a component of DNA.

For this reason, it is appropriately considered in itsown right, rather than as an analogue of any otherelement.

P





Terrestrial

Phosphorus shows only limitedparticle reactivity, and so can beexpected to move freelythrough the terrestrialenvironment, rather thanremaining in situ.

Aquatic

In aquatic ecosystems,phosphorus is present asparticulate organic phosphorus,dissolved inorganic phosphatesand dissolved organicphosphorus.

In most aquatic environments,particulate phosphorus is ingreatest abundance.

Atmospheric

If P-33 were released to theatmosphere, it would probablybe in the form of an aerosol.

Environmental sink

P-33 is sufficiently short-livedthat it will decay close to its siteof deposition in the terrestrialenvironment.

In the aquatic environment, P-33 is likely to decay mainly inthe water column, either insolution or incorporated inorganic particles.


P-33 deposited on land is likely to be highly available to plants, assoils typically contain only 0.65 ppm but plants contain about 1,000ppm.

It is highly available to animals, with gastrointestinal absorptionbeing almost complete.

In the short-term, phosphorus is widely distributed throughout alltissues. In the long-term, calcified tissues are the main reservoir.

In aquatic environments, very rapid uptake by organisms can beexpected, leading to concentration ratios relative to water of 10,000or more.


P-33 is a pure beta emitter.

Because of this and its high bioavailability, internalexposures will be of principal importance.

Although there may be some degree ofpreferential irradiation of calcified tissues, theeffect will be limited by the short half-life of theradionuclide.



P


Name


Parent

Protactinium-234m

1.2 minutes

Th-234

Symbol

Principal decaymode

Daughter

Pa-234m

Beta

U-234 [R]

Origin

Grouping

Detection

Radiogenic

Natural

Laboratory


Decay modes


Production • Naturally in all environmental media from the decay of U-238


Modes Land • Disposed uranium mill tailings

of Air • Only in circumstances where U-238/Th-234 is present in air

release Water • Only in circumstances where U-238/Th-234 is present in water

Speciation

Protactinium exists in aqueous solution in twooxidation states, +4 and +5, although the +5 statetends to be predominant.

Protactinium compounds tend to hydrolyse insolution.

Pa is not usually found in solution as a singlespecies, but appears as a mixture of complexesand hydrolysed species.

Analogue species

Pa-234m has a half-life of only 1.2 minutes andwill have little time to exhibit its environmentalchemistry.

Therefore, there is no need to identify analoguespecies.

P





Terrestrial

Pa-234m would be expected tobe present at close to the sameactivity equilibrium as its parentTh-234.

Aquatic

Pa-234m would be expected tobe present at close to the sameactivity concentration as itsparent Th-234. Th is particlereactive.

Atmospheric

Pa-234m would be expected tobe present in aerosols at close tothe same activity concentrationas its parent Th-234.

Environmental sink

Pa-234m would be expected todecay close to its site ofproduction.


Because of its very short half-life, Pa-234m would be present in biotaat close to the same activity concentration as its parent Th-234.

Therefore, intake and uptake of Pa-234m are of little relevancecompared with intake and uptake of its parent, Th-234.


Pa-234m is mainly a beta emitter, although thereis also a small amount of gamma emission.

Therefore, it is mainly of interest as an internallyincorporated radionuclide, as it will deliver moredose than its parent Th-234.



P


Name


Parent

Lead-210

22.3 years

Po-214

Symbol

Principal decaymode

Daughter

Pb-210

Beta

Bi-210 [R]

Origin

Grouping

Detection

Radiogenic

Natural

Laboratory


Decay modes


Production• Naturally in all environmental media from the decay of U-238• By product of uranium mining and milling

Uses • Determination of the age of lake and ocean sediments

ModesLand • Fallout from atmosphere following the decay of Rn-222

of Air• From burning coal• From decay in the atmosphere of Rn-222

releaseWater • Fallout from atmosphere following the decay of Rn-222

Speciation

Lead is found predominantly in the +2 oxidationstate in environmental waters.

It exists primarily as carbonato-, hydroxy- andchloro- complexes.

Lead also forms compounds with oxygen, thehalides and various organic molecules.

Analogue species

There are similarities between the chemistry andbiochemistry of Pb and Ca.

These can be useful mainly for interpretation ofspecific observations on Pb, rather than treating Pbas behaving in a generally analogous manner toCa throughout the environment.

P





Terrestrial

Pb-210 shows a very high levelof particle reactivity, and so canbe expected to remain in situ,rather than moving freelythrough the terrestrialenvironment.

Aquatic

Pb-210 is produced in aquaticsystems from the decay of Ra-226 via Rn-222 and its short-lived progeny.

Owing to its particle reactivity, itwill tend to bind to sediments.

Atmospheric

Pb-210 is produced in theatmosphere mainly from theprogeny of Rn-222. It is thensubject to deposition.

Environmental sink

In terrestrial systems, Pb-210typically decays close to its siteof production.

In aquatic systems, Pb-210tends to accumulate in bottomsediments


Pb-210 accumulates mainly on the external surfaces of plants, as itexhibits only a limited degree of bioavailability.

Lichens have very large surface areas per unit area of ground and canbe a major source of Pb-210 to grazing animals.

It is quite highly bioavailable to animals, with a fractionalgastrointestinal absorption ~20 % and is accumulated mainly incalcified tissues.

Aquatic biota exhibit concentration ratios relative to water of ~200 inboth marine and freshwater fish, and ~1,000 in marine molluscs,crustaceans and seaweed.


Pb-210 emits low-energy beta particles togetherwith a small amount of low energy photons.

Its short-lived daughter, Bi-210, is a pure betaemitter..

However, this then decays to Po-210, which is analpha emitter and is often a more importantcontributor to internal dose than is its ancestor Pb-210.


Naturally occurring Pb-210 is highly accumulatedin marine organisms and in organisms such asreindeer that graze on plants with a high surfacearea per unit area of land such as lichens.

P


Name


Parent

Promethium-147

2.6 years

N/A

Symbol

Principal decaymode

Daughter

Pm-147

Beta

Sm-147 [R]

Origin

Grouping

Detection

Fission

Artificial

Laboratory


Decay modes



Uses• As a beta source for thickness gauges• As a coating for self-luminous watch dials• Potentially as a heat source for space probes and satellites




Speciation

Promethium is a rare earth element that shows anoxidation state of +3, and whose compounds aretypical of other rare earth compounds.

As such, promethium forms compounds withhydrogen, oxygen and the halides.

It also forms stable complexes.

Analogue species

There are considerable similarities in the chemistry,biochemistry and biogeochemistry of all thelanthanide elements.

In particular, Ce, Sm and Eu are moderatelyextensively studied elements that are analogous toPm.

P





Terrestrial

Pm-147 is highly particlereactive, and hence wouldremain bound to soil particlesand on the surfaces of plants.


Aquatic

Pm-147 is highly particlereactive in the aquaticenvironment.

It is likely to bind to suspendedsediments close to its point ofdischarge and migrate lost fromthe water column by depositionof those sediments.

Atmospheric

If Pm-147 was released to theatmosphere, it would be as anaerosol and probably in oxideform.

Environmental sink

The high particle reactivity ofPm-147 mean that it is likely todecay close to its site ofdeposition in terrestrialenvironments.



Pm-147 is not very bioavailable to animals. The fractionalgastrointestinal absorption is typically <0.001. Any Pm-147 that isabsorbed is mainly deposited in the liver and skeleton.

Intake by terrestrial animals is likely to be mainly the ingestion of Pm-147 present on the exterior surfaces of plants or deposited onsoil.


In the aquatic environment uptake by fish and invertebrates is mainlydirect from the water rather than food. Uptake by aquatic plants islikely to be by surface adsorption.


Pm-147 is almost exclusively an emitter of low-energy beta particles.

External deposits of Pm-147 on plants and animalswill only result in irradiation of superficial outertissues, which are often unsensitive to radiationexposure.

Internal exposure will be limited by the lowbioavailability of Pm-147.


The high uptakes in molluscs, crustaceans andaquatic plants could be important.

P


Name


Parent

Polonium-210

138 days

Bi-210

Symbol

Principal decaymode

Daughter

Po-210

Alpha

Pb-206

Origin

Grouping

Detection

Radiogenic

Natural

Laboratory


Decay modes


Production• Naturally in all environmental media from the decay of U-238• By product of uranium mining and milling

Uses • Source of electric power for space vehicles

ModesLand • Disposed uranium mill tailings

of Air• From burning coal• During treatment of spent fuel

releaseWater • During treatment of spent fuel

Speciation

Polonium is a Group VI element that formscompounds with the halogens, hydrogen, andoxygen to produce a range of oxides.

All polonium compounds hydrolyse in water.

Analogue species

Po-210 is the daughter of Pb-210.

Its environmental behaviour is stronglyconditioned by that of its parent.

As extensive environmental studies have beenundertaken relating to Pb-210 and Po-210, it isnot appropriate to rely on analogues.

P





Terrestrial

Po-210 is formed in theterrestrial environment fromdeposited Pb-210.

Po-210 is highly particlereactive, so will tend to remainin situ rather than migrating insurface or groundwaters.

Aquatic

Po-210 is produced in aquaticsystems from the decay of Pb-210.

Owing to its particle reactivity, itwill tend to bind to sediments.

Atmospheric

Po-210 can be formed from Pb-210 in the atmosphere.

However, as the mean residencetime of dust suspended in thetroposphere is only about 15days, there is little time for itsingrowth in the atmosphere.

Environmental sink

Pb-210 typically decays close toits site of production from Pb-210.


Po-210 is not very available to plants.

The fractional gastrointestinal absorption of Po-210 in mammals istypically ~10 %.

Po-210 entering the systemic circulation is widely distributed in softtissues. Although it has no particular affinity for bone, it is oftenfound there in higher concentrations than in other tissues, havingbeen produced by decay of Pb-210.

Concentrations of Po-210 in aquatic foods are typically similar to, orrather higher than, those of Pb-210.

For fish products, UNSCEAR (2000) gives reference concentrations forPo-210 of 2 Bq/kg.


Po-210 is primarily an alpha emitter.


Therefore, Po-210 is of greatest potentialsignificance when internally incorporated inorgans and tissues that are susceptible to theeffects of alpha radiation.


No species-specific considerationsP


Name


Parent

Plutonium-238

87.7 years

Cm-242

Symbol

Principal decaymode

Daughter

Pu-238

Alpha

U-234 [R]

Origin

Grouping

Detection

Breeding

Artificial

Laboratory


Decay modes


Production• Formed by neutron activation of uranium in a nuclear reactor, followed by

decay of the activation products

Uses• As a power source for satellites and other space equipment• As a power source for heart pacemakers

ModesLand

• Deposition to soils as a result of weapons testing• Releases from nuclear reactors or experimental facilities

ofAir

• Releases due to weapons testing• Releases from nuclear reactors or experimental facilities

releaseWater • Releases from nuclear reactors or experimental facilities

Speciation

In aqueous solution, plutonium can exhibit any offour oxidation states.

The stable oxidation state(s) in any solution are afunction of environmental conditions such as pHand Eh.

Plutonium reacts slowly with water and rapidlywith dilute acids.

It forms halide and oxide compounds.

Analogue species

There are chemical, biochemical andbiogeochemical similarities between Pu andvarious other actinides, notably Np, Am and Cm.

However, the environmental behaviour of Pu hasbeen studied more extensively than those otheractinides, so there is little merit in using them asanalogues for Pu.

P





Terrestrial

Pu-238 is highly particle reactiveand therefore binds strongly tosoils and sediments.


Aquatic

Pu-238 is also highly particlereactive in the aquaticenvironment and thereforetends to bind to suspendedsediments and hence migrate tobottom sediments.

Atmospheric

Pu-238 would be expected todisperse as an aerosol.


Environmental sink

Because of its high particlereactivity, Pu-238 will tend toremain in such soil systems untilit decays.

In aquatic systems, bottomsediments are the most likelyenvironmental sink.


Pu-238 is strongly excluded from plants and is mainly present ontheir surfaces as external contamination.


Uptake from the gastrointestinal tract is limited (<0.1 %), althoughenhanced concentrations of Pu-238 may occur in the liver andskeleton.

Concentrations in marine and freshwater fish are only about a factor30 higher than concentrations in water. However, concentrations inmolluscs, crustaceans and aquatic plants can be a factor of 300 ormore higher than the surrounding water.


Pu-238 is primarily an alpha emitter.


Therefore, Pu-238 is of greatest potentialsignificance when internally incorporated inorgans and tissues that are susceptible to theeffects of alpha radiation.




Name


Parent

Plutonium-239

2.4 x 104 years

Np-239

Symbol

Principal decaymode

Daughter

Pu-239

Alpha

U-235 [R]

Origin

Grouping

Detection

Breeding

Artificial

Laboratory


Decay modes


Production• Formed by neutron activation of uranium in a nuclear reactor, followed by decay

of the activation products

Uses• As the basic fuel for fast breeder reactors• The source of explosive power in nuclear weapons

ModesLand

• Deposition to soils as a result of weapons testing• Releases from nuclear reactors or experimental facilities

ofAir



Speciation





Analogue species



P





Terrestrial



Aquatic


Atmospheric



Environmental sink

Because of its high particlereactivity, Pu-239 will tend toremain in such soil systems.














Name


Parent

Plutonium-240

6,537 years

Cm-244

Symbol

Principal decaymode

Daughter

Pu-240

Alpha

U-236 [R]

Origin

Grouping

Detection

Breeding

Artificial

Laboratory


Decay modesChemical properties/characteristics



Uses • No significant commercial uses

Modes Land• Deposition to soils as a result of weapons testing• Releases from nuclear reactors or experimental facilities

ofAir


releaseWater • Releases from nuclear reactors or experimental facilities

Speciation





Analogue species



P





Terrestrial



Aquatic


Atmospheric

Pu-240 would be expected todisperse as an aerosol. The mostlikely chemical form would bean oxide, but other forms, e.g.nitrate, might also arise.

Environmental sink















Name


Parent

Plutonium-241

14.4 years

Cm-245

Symbol

Principal decaymode

Daughter

Pu-241

Beta

Am-241 [R]

Origin

Grouping

Detection

Breeding

Artificial

Laboratory


Decay modesChemical properties/characteristics



Uses • No significant commercial uses

Modes Land• Deposition to soils as a result of weapons testing• Releases from nuclear reactors or experimental facilities

ofAir



Speciation





Analogue species



P





Terrestrial



Aquatic


Atmospheric



Environmental sink









Pu-241 is primarily an emitter of very low energybeta particles.

Therefore, Pu-241 is of greatest potentialsignificance when internally incorporated.

Internally incorporated Pu-241 may be lessimportant dosimetrically than its decay productAm-241 because of the intense alpha emissions ofthe latter.




Name


Parent

Radium-226

1,600 years

Th-230

Symbol

Principal decaymode

Daughter

Ra-226

Alpha

Rn-222 [R]

Origin

Grouping

Detection

Radiogenic

Natural

In situ


Decay modes


Production• Naturally in all environmental media through the decay of U-238• By product of uranium mining and milling

Uses• In sealed sources for the treatment of cancer• Historically, used as a component of luminous paint and in lightening conductors

Modes Land• Disposed uranium mill tailings• Disposal of luminising waste (past practices)

ofAir

• From burning coal• As part of spent fuel

releaseWater • As part of spent fuel

Speciation

Radium is an alkaline earth element and, as aconsequence, the most important species is theRa2+ ion.

Isotopes of radium can therefore be expected totake part in a number of precipitation andsubstitution reactions.

Precipitation as sulphate, carbonate or hydroxideis possible.

Analogue species

The alkaline earth elements Ca, Sr, Ba and Raexhibit close chemical, biochemical andbiogeochemical analogies.

However, Ra has been studied extensively in itsown right, so it is not necessary to rely onanalogies with the other alkaline earths.

R





Terrestrial

Ra-226 is widely dispersed insoils due to the presence of U-238. It mainly decays in situ,as it is incorporated in themineral phase.

Ra-226 is strongly excludedfrom plants.

Aquatic

The Ra-226 content of surfacewaters is low and it has only alimited tendency to bind withsediments.

However, highly insoluble Ba/Rasulphates may be precipitated inthe context of uraniumprocessing.

Atmospheric

Ra-226 is not generally of greatinterest in the context ofatmospheric releases, althoughit could be dispersed fromfacilities where uranium oreshave been processed.

Environmental sink

Most Ra-226 decays local to itspoint of production from decayof primordial U-238.

However, Ra-226 enteringsurface waters may either decayin the water column or betransferred to sediments.

High concentrations of Ra-226may accumulate in tailingsponds at uranium oreprocessing facilities.


Ra-226 is strongly excluded from plants.

Its fractional gastrointestinal absorption in mammals is typically only~3 %.

Ra-226 entering the systemic circulation is mainly accumulated inmineral bone.

Ra-226 exhibits concentration ratios relative to water of about 50 inboth marine and freshwater fish. It accumulates in the bone, scalesand fins.

Concentration ratios in marine invertebrates range from 3 to 7,000.Typical values are 100 for molluscs and 1,000 for crustaceans.


Ra-226 is primarily an alpha emitter.


Thus, Ra-226 is of greatest potential significancewhen internally incorporated in organs and tissuesthat are susceptible to the effects of alpharadiation.

Ra-226 decays to Rn-222. Although much of thisRn-222 diffuses out of the body, some remainstrapped and decays in situ.



R


Name


Parent

Rubidium-81

4.6 hours

N/A

Symbol

Principal decaymode

Daughter

Rb-81

EC

Kr-81 [R]

Origin

Grouping

Detection

Fission

Artificial

In situ


Decay modes


Production • By irradiation of stable precursors in a cyclotron or nuclear reactor

Uses • In the production of krypton-81 (the decay product)



release Water • Hospital releases to sewers, but would probably decay away before this can occur

Speciation

Rubidium is an alkali metal whose chemicalbehaviour is determined by the properties of theRb+ ion.

Most of the compounds of rubidium are ionic innature, although more complex species can beformed.

Analogue species

Rb has no known biological role, but it is a closechemical analogue for K and can substitute for it,to some degree, in biota.

In terms of binding to soils and sediments, both Kand Cs are useful analogues.

R





Terrestrial

Rubidium is moderately particlereactive and so a substantialproportion will remain in situ.

A limited amount will betransported around theterrestrial environment insurface and groundwaters.

Aquatic

Freshwater sediments mayabsorb Rb-81 significantly. But islikely to behave conservativelyin the marine environment.

Atmospheric

It is likely to be released as anaerosol, but its very short half-life will limit the amount ofdeposition to plants and groundsurfaces

Environmental sink

Because of its short half-life Rb-81 in the terrestrialenvironment will decay close toits point of deposition.

In aquatic environments, Rb-81will mainly decay in the watercolumn as it disperses, orpossibly in deposited freshwatersediments.


The very short radioactive half-life of Rb-81 will preclude substantialuptake by plants.

Rb-81 is highly bioavailable to animals and would be efficientlyabsorbed by animals grazing on externally contaminated vegetation.

It would rapidly become relatively uniformly distributed throughoutthe bodies of those animals.

Concentration ratios relative to water are likely to be much higher infreshwater than marine organisms, although the very short half-life ofRb-81 would limit the extent of accumulation.


Rb-81 is a positron emitter. Therefore, there is astrong 0.511 MeV gamma ray emission.

External exposure will therefore be an importantexposure pathway.

Rb-81 taken up by biota would be relativelyuniformly distributed throughout their tissues, soindividual organ and tissue doses would be ofsimilar magnitude to the average whole-bodydose.


As Rb-81 is a chemical analogue for K, which is anessential element for almost all biota, there are nomajor species-specific considerations.

R


Name


Parent

Rubidium-86

18.7 days

N/A

Symbol

Principal decaymode

Daughter

Rb-86

Beta

Sr-86

Origin

Grouping

Detection

Fission

Artificial

In situ


Decay modes



Uses • In medicine for the determination and treatment of electrolyte disorders




Speciation

Rubidium is an alkali metal whose chemicalbehaviour is determined by the properties of theRb+ ion.

Most of the compounds of rubidium are ionic innature, although more complex species can beformed.

Analogue species

Rb has no known biological role, but it is a closechemical analogue for K and can substitute for it,to some degree, in biota.

In terms of binding to soils and sediments, both Kand Cs are useful analogues.

R





Terrestrial

Rubidium is moderately particlereactive and so a substantialproportion will remain in situ.

A limited amount will betransported around theterrestrial environment insurface and groundwaters.

Aquatic

Freshwater sediments mayabsorb Rb-86 significantly. But islikely to behave conservativelyin the marine environment.

Atmospheric

Rb-86 is likely to be released asan aerosol and may bedeposited on plants and soils bywet and dry depositionprocesses.

Environmental sink

Because of its short half-life, Rb-86 in the terrestrialenvironment will decay close toits point of deposition.

In aquatic environments, Rb-86will mainly decay in the watercolumn as it disperses, orpossibly in deposited freshwatersediments.


Significant rapid, metabolically active foliar absorption of Rb-86deposited on plants is likely to occur.

Rb-86 is highly bioavailable to animals and would be efficientlyabsorbed by animals grazing on externally contaminated vegetation.

It would rapidly become relatively uniformly distributed throughoutthe bodies of those animals.

Concentration ratios relative to water are likely to be much higher infreshwater than marine organisms. For freshwater organisms, valuesof a few hundred are typical.


Rb-86 taken up by biota would be relativelyuniformly distributed throughout their tissues, soindividual organ and tissue doses would be ofsimilar magnitude to the average whole-bodydose.


As Rb-86 is a chemical analogue for K, which is anessential element for almost all biota, there are nomajor species-specific considerations.

R


Name


Parent

Rhenium-186

3.7 days

N/A

Symbol

Principal decaymode

Daughter

Re-186

Beta

Os-186 [R]

Origin

Grouping

Detection

Activation

Artificial

Laboratory


Decay modes


Production • Produced by irradiation of stable precursors in a cyclotron or nuclear reactor

Uses• To provide pain relief from bone cancer• In the treatment of rheumatoid arthritis

Modes Land• Sewage sludge application to land, but would probably decay substantially




Speciation

Rhenium is a Group VII element that can showoxidation states from -1 through to +7.

It forms compounds with the halogens andoxygen, and can form an extensive range ofcomplexes, of which many contain bonds withoxygen or nitrogen.

Analogue species

Almost nothing is known about the environmentalbehaviour of Re.

Although there are chemical similarities with Tc,both elements have complex, redox-dependentchemistries and it would not be appropriate to relyon Tc as an environmental analogue for Re.

R





Terrestrial

Re-186 is most likely to enterthe terrestrial environment byatmospheric deposition.

It is likely to exhibit only limitedparticle reactivity in oxicconditions.

Aquatic

As for the terrestrialenvironment, Re-186 is likely toexhibit only limited particlereactivity in oxic conditions.

Atmospheric

If Re-186 were released to theatmosphere, it would disperse asan aerosol.

Environmental sink

In the terrestrial environment,Re-186 is likely to decay close toits site of deposition.

In the aquatic environment, it islikely to decay as it disperses inthe water column.


Foliar uptake of Re-186 could occur, but its short half-life means thatit will mainly be present on the external surfaces of plants.

Re-186 ingested by animals is likely to be highly bioavailable andwidely dispersed throughout soft tissues.

Re-186 may exhibit high concentration ratios relative to water inmarine invertebrates and seaweed.

However, its short half-life may prevent such ratios being achieved.


Re-186 is mainly a beta emitter.

However, a small amount of gamma emission alsooccurs.

Because of its potentially high bioavailability, thepathway of greatest interest may possibly beinternal exposure of animals.


Insufficient information is available to permit anycomment to be made.

R


Name


Parent

Radon-222

3.8 days

Ra-226

Symbol

Principal decaymode

Daughter

Rn-222

Alpha

Po-218 [R]

Origin

Grouping

Detection

Radiogenic

Natural

In situ


Decay modes


Production • From the decay of radium-226 in the uranium-238 decay chain

Uses • Sometimes used in sealed tubes in the treatment of cancer

Modes Land • Naturally present in soil and rock pores containing uranium

of Air • Emitted from soils and rocks containing uranium

release Water • Naturally present in waters containing radioactive precursors

Speciation

Radon is a noble gas and, as such, forms only alimited number of chemical compounds due to itslack of reactivity.

One such example is RnF2.

Analogue species

There are broad similarities in the behaviour of allthe noble gases (Ne, Ar, Kr, Xe, Rn).

However, Rn-222 is characterised by various short-lived, chemically reactive and radioactive progeny.

As it has been studied extensively in its own right,there is no need to resort to analogies.

R





Terrestrial

Rn-222 is not deposited to asignificant degree in terrestrialenvironments.

Its short-lived descendants dodeposit to surfaces, but this ismainly relevant in mitigatinginhalation exposures (dosesfrom Rn-222 inhalation aredominated by the decay ofshort-lived descendants).

Aquatic

Rn-222 is produced from Ra-226 in aquatic environments,but is of little radiologicalsignificance compared with itslong-lived descendants, Pb-210and Po-210.

Atmospheric

Rn-222 is produced from Ra-226present in soils and sedimentsand is subsequently released tothe atmosphere.

Outdoor concentrations vary byabout a factor of 100,depending on the geographicalcontext and near-surfaceuranium concentrations.

Concentrations are higher inenclosed spaces, e.g. burrows.

Environmental sink

Rn-222 released from soils andsediments decays mainly in theatmosphere.

However, much of the Rn-222produced in soils and sedimentsdecays in situ.

Rn-222 produced at depths ofmore than about 0.3 m haslittle chance of escaping fromthe soil surface.


The main intake route for Rn-222 and its short-lived progeny isinhalation.

Being a noble gas, very little radon is retained in the body.

However, short-lived descendants can settle and attach themselves tothe lung surface.


Rn-222 and its short-lived progeny emit a mixtureof alpha, beta and gamma radiation.

In animals, short-lived progeny of Rn-222 depositon, and preferentially irradiate, the surfaces of thetrachea and bronchi.


Rn-222 is mainly of interest in respect of terrestrialanimals.

Exposures of burrow-dwelling animals are ofparticular importance.

R


Name


Parent

Ruthenium-106

373.6 days

N/A

Symbol

Principal decaymode

Daughter

Ru-106

Beta

Rh-106 [R]

Origin

Grouping

Detection

Fission

Artificial

Laboratory


Decay modes


Production • Produced as a result of fission processes in a nuclear reactor

Uses • Sometimes used in medical research and diagnostics

ModesLand • Reaches surface soils as a result of sewage sludge applied to land

ofAir • Sometimes released from nuclear reactors, hospitals and research facilities

release Water• Sometimes released from nuclear reactors, hospitals and research facilities• Liquid discharges from nuclear facilities

Speciation

Ruthenium is a platinum metal that showsoxidation states from -2 through to +8; theprincipal ones are +2 and +3.

Ruthenium forms compounds with the halogensand oxygen.

It can also form various complexes, of which thoseinvolving bonding to nitrogen are the most stable.

Analogue species

There are broad similarities in the behaviour of allthe noble gases (Ne, Ar, Kr, Xe, Rn).

However, Rn-222 is characterised by various short-lived, chemically reactive and radioactive progeny.

As it has been studied extensively in its own right,there is no need to resort to analogies.

R





Terrestrial

Ru-106 is moderately adsorbedin mineral soils, but is stronglyadsorbed in organic soils.

In mineral soils, cationic formsadsorb much more stronglythan anionic forms.

Nitrogen-ruthenium complexesare only poorly adsorbed andare available for plant uptake.

Aquatic

Ru-106 is highly particlereactive, although the degree ofsorption to freshwatersediments is much less than tomarine sediments.

In seawater, almost no Ru ispresent in ionic form.Particulate-bound and colloidalRu are dominant.

Atmospheric

If Ru-106 were to be released toatmosphere, it would be as anaerosol.

Environmental sink


In terrestrial environments, Ru-106 can be expected to decayclose to its site of deposition.

In freshwater environments, itmay be transported as ionic orcolloidal forms.

In the marine environment,decay will occur in the watercolumn or deposited sediments.


In terrestrial environments, uptake to plants from foliar absorption islikely to be more important than root uptake in the first season afterdeposition.

The fractional gastrointestinal absorption of Ru in mammals is <10 %.

Ru-106 entering the systemic circulation becomes relatively uniformlydistributed and is well retained.

Concentration ratios relative to water are <10 for the soft tissues ofcrustaceans, but ~100 for whole animals. For molluscs, soft tissueand whole body ratios are 500 and 2,000, respectively. In fish, wholebody ratios are typically between 10 to 100.


Ru-106 is a soft beta emitter.

However, it decays to the very short-lived Rh-106,which emits energetic beta particles andmoderately energetic gamma rays.

Internal and external exposures from Ru-106/Rh-106 should be taken into account.


Molluscs and crustaceans accumulate Ru-106 intheir guts and external organs.

Uptake to the shell can be particularly important.

R


Name


Parent

Sulphur-35

87.3 days

P-35

Symbol

Principal decaymode

Daughter

S-35

Beta

Cl-35

Origin

Grouping

Detection

Activation

Artificial

Laboratory


Decay modes


Production• By irradiation of stable isotopes of sulphur and carbon with neutrons in a nuclear

reactor or cyclotron

Uses • Used in research as a radiotracer

ModesLand • Deposition from air onto surface soils

ofAir • Released from gas-cooled nuclear reactors

release Water• Release to sewers• Leaching to groundwater from surface soils

Speciation

Sulphur can exhibit oxidation states of -2, 0, +2,+4 and +6.

It can thus form a wide range of compounds,particularly with the halogens.

Sulphur also has a great tendency towardscatenation (the formation of element-elementbonds).

Analogue species

Sulphur is an essential element for all livingorganisms.

There are extensive studies of its behaviour in theenvironment and it is inappropriate to consider itby analogy with any other element.

S





Terrestrial

S-35 is likely to enter theterrestrial environment bydeposition from theatmosphere.

S-35 as SO2 is strongly taken upby plants through foliarabsorption and is reduced toorganic sulphur compounds.

The mechanism of depositionand uptake is affected byseasonal factors.

Aquatic

The majority of sulphur inseawater is present as sulphateand little is thought to bepresent as particulates.

Concentrations of sulphur infreshwaters are generally muchlower than those in marinewaters.

Atmospheric

S-35 is likely to be released tothe atmosphere as the gasesCOS or SO2.

However, it could also bereleased as a particulate aerosol,e.g. sulphate.

Environmental sink

S-35 is mainly of interest in theterrestrial environment.

It will mainly be accumulatedby plants and soils and willdecay in situ.


S-35 will be rapidly and efficiently taken up in plants by foliarabsorption.

It is highly available to animals, gastrointestinal absorption beingvirtually complete.

S-35 entering the systemic circulation from diet is uniformlydistributed in the body and is well retained.

Concentration ratios in aquatic organisms relative to water are ~0.5and 100 for marine and freshwater organisms, respectively.


S-35 is a pure beta emitter and is only of interestin the context of internal irradiation.

As it is relatively uniformly distributed in plantsand animals, doses to individual organs and tissueswill be of similar magnitude to average whole-body doses.



S


Name


Parent

Antimony-125

2.8 years

N/A

Symbol

Principal decaymode

Daughter

Sb-125

Beta [gamma]

Te-125m [R],Te-125

Origin

Grouping

Detection

Fission

Artificial

In situ


Decay modes







Speciation

Antimony is a metalloid of Group V, whosechemistry is dominated by the +3 and +5oxidation states.

Antimony forms compounds with hydrogen,oxygen, sulphur, halides and other elements.

It can form antimonyl compounds involvingantimony and oxygen (SbO)+.

Analogue species

Sb exhibits some chemical and biochemicalsimilarities to arsenic.

However, there are also considerable differencesand the environmental behaviour of Sb is besttreated without reference to potential analogues.

S





Terrestrial

In general, when Sb-125 isadded to soils in soluble form, itcan be expected to remainmobile as it is, at most,moderately particle reactive.

Sb-125 is not very available toplants.

Aquatic

Sb-125 is likely to be present inboth fresh and marine watersmainly in ionic form.

However, a substantial fractionmay become bound tosuspended and bottomsediments.

Atmospheric

If Sb-125 were released to theatmosphere, it would probablybe as an aerosol rather than thehighly toxic gas stibine (SbH3).

Environmental sink

In the terrestrial environment,some migration of Sb-125 inthe soil profile can be expectedbefore it decays.

In aquatic environments, decaywill occur mainly in the watercolumn and only to a limiteddegree in deposited sediments.


Sb-125 is not very available to plants and there is no evidence ofsubstantial foliar uptake.

The fractional gastrointestinal absorption in mammals is typically ~1 %.

Antimony is widely distributed in the soft tissues of mammals, butbone is the main long-term reservoir.

Concentration ratios of Sb-125 in aquatic organisms relative to waterare typically in the range 5 to 100.


Sb-125 is a mixed beta-gamma emitter.

Gamma emissions are of high yield and moderateenergy.

Because of the low bioavailability of Sb-125,external irradiation may be more important thaninternal irradiation in terrestrial environments.



S


Name


Parent

Selenium-75

120 days

N/A

Symbol

Principal decaymode

Daughter

Se-75

EC

As-75

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes



Uses• In medicine for diagnostic imaging• To investigate the production of digestive enzymes

ModesLand • Sewage sludge application to land

of Air• Not generally released to air, but some releases of volatile selenium compounds

may occur from sewage sludgerelease


Speciation

Selenium can exist in one of four oxidation states:-2 (selenide compounds), 0 (elemental selenium),+4 (selenite compounds) and +6 (selenatecompounds).

Selenide and elemental selenium are expected tobe present in reducing conditions, with seleniteand selenate species appearing as conditions movetowards oxidising.

Analogue species

There are considerable similarities between thechemistry and biochemistry of Se and S, and Secan substitute for S in a number of contexts.

However, Se is an essential trace element in itsown right, so this analogy should be usedcautiously.

S





Terrestrial

The chemistry of Se in soils iscomplex, but it can bindstrongly to clay minerals. Theproportion of available Se insoils can vary from <1 % to 30 %.

There are strong distinctionsbetween normal and Se-deficient soils.

Selenate is likely to be muchmore available than selenite.

Aquatic

Se-75 in aquatic systems ismoderately particle reactive.

Binding to sediments dependson the acidity and the Fe, Mnand clay contents of thesediments.

Atmospheric

Se-75 could be released toatmosphere either as an aerosolor as a gas, e.g. dimethylselenide.

Environmental sink

Se-75 deposited in theterrestrial environment is likelyto be strongly retained in theplant-soil system and decayclose to its point of deposition.

In aquatic systems, it may decayeither in the water column or inbottom sediments, dependingon the chemical form.


Se-75 is very highly bioavailable to both terrestrial plants and animals(especially as selenate) and is likely to be substantially accumulated,particularly in Se-deficient conditions.

Both foliar uptake and root absorption are likely to be important inplants.

Se is widely distributed in animal tissues and is well retained.

Concentration ratios relative to water are ~100 for most aquaticorganisms.


Se-75 is predominantly a gamma-emittingradionuclide.

However, because of its high bioavailability andrelatively long half-life, internal irradiation is likelyto be more important than external irradiation,especially for small organisms.



However, Se-deficient terrestrial environments arelikely to be associated with an exceptionally highdegree of bioavailability of Se-75.

S


Name


Parent

Samarium-153

46.7 hours

N/A

Symbol

Principal decaymode

Daughter

Sm-153

Beta

Eu-153

Origin

Grouping

Detection

Activation

Artificial

Laboratory


Decay modes


Production• Produced during fission in a nuclear reactor• By irradiating stable precursors in a cyclotron

Uses• In medicine for relieving pain from secondary bone cancers• For diagnostic imaging and radioimmunotherapy




Speciation

Samarium is a rare earth element that showsoxidation states of +2 and +3, and whosecompounds are typical of other rare earthcompounds.

As such, samarium forms compounds withhydrogen, oxygen and the halides. It also formsstable complexes.

Analogue species

There are considerable similarities in the chemistry,biochemistry and biogeochemistry of all thelanthanide elements.

In particular, Ce and Eu are moderately extensivelystudied elements that are analogous to Sm.

S





Terrestrial

Sm-153 is highly particlereactive, and hence wouldremain bound to soil particlesand on the surfaces of plants.


Aquatic

Sm-153 is highly particlereactive in the aquaticenvironment.

It is likely to bind to suspendedsediments close to its point ofdischarge, and deposit from thewater column to bottomsediments.

Atmospheric

If Sm-153 was released to theatmosphere, it would be as anaerosol and probably in oxideform.

Environmental sink

The short half-life and highparticle reactivity of Sm-153mean that it is likely to decayclose to its site of deposition interrestrial environments.



Intake by terrestrial animals is likely to be mainly the ingestion of Sm-153 present on the exterior surfaces of plants or deposited on soil.

Sm-153 is not very bioavailable to animals. The fractionalgastrointestinal absorption is typically <0.1 %.

Any Sm-153 that is absorbed is mainly deposited in the liver andskeleton.



Sm-153 is mainly an emitter of low-energy betaparticles.

External deposits of Sm-153 on plants and animalswill mainly result in irradiation of superficial outertissues, which are often insensitive to radiationexposure.

Internal exposure will be limited by the lowbioavailability of Sm-153.


The high uptakes in molluscs, crustaceans andaquatic plants could be important.

S


Name


Parent

Strontium-89

50.5 days

N/A

Symbol

Principal decaymode

Daughter

Sr-89

Beta

Y-89

Origin

Grouping

Detection

Fission

Artificial

Laboratory


Decay modes


Production• Produced as a fission product in a nuclear reactor• In a cyclotron for medical purposes

Uses • Used in medicine to treat metastases in bone cancer




Speciation

Strontium is an alkaline earth element and thusthe most important species is the Sr2+ ion.

Isotopes of strontium can therefore be expected totake part in a number of precipitation andsubstitution reactions.


Analogue species

The alkaline earths Ca, Sr, Ba and Ra exhibitconsiderable chemical, biochemical andbiogeochemical similarities.

Ratios of Sr-90 to stable Ca have often been usedto characterise the environmental behaviour of theradionuclide.

S





Terrestrial

Sr-89 is only weakly tomoderately particle reactive insoils.

However, its degree of mobilityis limited by its short half-life.

Foliar uptake of Sr-89 uptakecan be significant.

Aquatic

Sr-89 has only a limitedtendency to bind to sedimentsin either freshwater or marinesystems.

Atmospheric

Sr-89 would be expected todisperse as an aerosol.

Environmental sink

Although Sr-89 is relativelymobile, its short half-life meansit will largely decay in situ interrestrial environments.

However, in freshwater andmarine environments, it may bewidely dispersed beforedecaying, largely in the watercolumn.


Sr-89 is moderately bioavailable to plants. Foliar uptake can besignificant.

Strontium is moderately bioavailable to animals, with a fractionalgastrointestinal absorption of ~20 %.

There is considerable early retention in soft tissues. However, thelong-term reservoir for accumulation is bone.

It is only very weakly accumulated by aquatic organisms, typicallyexhibiting concentration ratios relative to water in the range 1 to 5.


Sr-89 is almost a pure beta emitter.

Therefore, externally deposited Sr-89 onlyirradiates superficial tissues, which are not alwaysvery radiosensitive.

However, the radionuclide is relatively highlybioavailable, so internal irradiation is likely to bethe dominant consideration in animals.

In plants, either external or internal irradiationmay be more important, depending on themorphology and physiology of the plant, and thecharacteristics of the deposit.


Accumulation in terrestrial animals seems likely tobe of greater interest than uptake in terrestrialplants or aquatic organisms.

S


Name


Parent

Strontium-90

29.1 years

N/A

Symbol

Principal decaymode

Daughter

Sr-90

Beta

Y-90 [R]

Origin

Grouping

Detection

Fission

Artificial

Laboratory


Decay modes



Uses • As an energy source for powering remote machinery e.g. satellites• In medicine for the treatment of cancer

Modes Land • Deposition onto soils from weapons testing or nuclear accidents

of Air • As a result of a nuclear accident or historic weapons testing

release Water • Liquid discharges from nuclear facilities

Speciation

Strontium is an alkaline earth element and thusthe most important species is the Sr2+ ion.

Isotopes of strontium can therefore be expected totake part in a number of precipitation andsubstitution reactions.


Analogue species

The alkaline earths Ca, Sr, Ba and Ra exhibitconsiderable chemical, biochemical andbiogeochemical similarities.

Ratios of Sr-90 to stable Ca have often been usedto characterise the environmental behaviour of theradionuclide.

S





Terrestrial

Sr-90 is only weakly tomoderately particle reactive insoils.

Foliar uptake of Sr-90 uptakecan be significant, but theradionuclide tends to remain inthe plant part where it wasdeposited and does not becomewidely translocated.

Aquatic

Sr-90 has only a limitedtendency to bind to sedimentsin either freshwater or marinesystems.

Atmospheric


Environmental sink

Although Sr-90 is relativelymobile, it can often remain insoils and sediments close to itspoint of deposition until itdecays.

However, in freshwater andmarine environments, it may bewidely dispersed beforedecaying in the water columnand bottom sediments.


Sr-90 is moderately bioavailable to plants.

Strontium is moderately bioavailable to animals, with a fractionalgastrointestinal absorption of ~20 %.

There is considerable early retention in soft tissues. However, thelong-term reservoir for accumulation is bone.

It is only very weakly accumulated by aquatic organisms, typicallyexhibiting concentration ratios relative to water in the range 1 to 5.


Sr-90 and its short-lived daughter Y-90 are almostpure beta emitters.

However, the beta particles from Y-90 areparticularly energetic, so more penetration ofsuperficial tissues from external deposits occursthan with most beta emitters.

However, Sr-90 is relatively highly bioavailable andlong-lived, so internal irradiation is likely to be thedominant consideration in both plants andanimals.


Accumulation in terrestrial animals seems likely tobe of greater interest than uptake in terrestrialplants or aquatic organisms.

S


Name


Parent

Technetium-99

2.1 x 105 years

Mo-99, Tc-99m

Symbol

Principal decaymode

Daughter

Tc-99

Beta

Ru-99

Origin

Grouping

Detection

Fission

Artificial

Laboratory


Decay modes



Uses • Sometimes used to reduce corrosion of steels

Modes Land • Present in soils due to fallout from weapons testing

of Air • Discharged to air from operating nuclear reactors

release Water • Liquid discharges from nuclear facilities

Speciation

Technetium can exist in a number of oxidationstates, although +7 and +4 are the most stableforms in solution.

In oxidising conditions, the pertechnetate ion(TcO4

-) is the most stable form. It gives rise to saltsthat are stable in the pH range 0 to 14, and whichare generally very soluble.

In reducing conditions, oxides of technetium arethe dominant form of the element.

Analogue species

Technetium exhibits complex chemical,biochemical and biogeochemical interactions.

It is, therefore, strongly recommended thatanalogies be used only with extreme caution whenattempting to characterise the environmentalbehaviour of technetium.

T





Terrestrial

Tc-99 could be stronglyaccumulated in stronglyreducing soils and sediments.

In oxic conditions, however, it islikely to be present as thepertechnetate and to be highlymobile.

Aquatic

Tc-99 reacts only weakly withparticulate matter in oxidisingconditions, but can be highlyparticle reactive in reducingconditions.

Discharges to freshwater,estuarine or marineenvironments would beexpected to disperse widely,mixing throughout the worldísoceans in the long term.

Atmospheric


Environmental sink

Because of its redox-sensitivecharacteristics, highly reducedsoils and sediments can be asink for Tc-99.

However, if the Tc remains inoxic form, it is likely to behighly mobile.

In the marine environment, itwill largely remain present inthe water column until itdecays.


In oxic conditions, Tc-99 is highly available to plants andconsiderable accumulation can occur.

Tc can be highly available to animals, with fractional gastrointestinalvalues approaching 100 %.

Tc entering the systemic circulation is widely distributed throughoutsoft tissues, but is not well retained.

Concentration ratios relative to water for Tc are about 30 forfreshwater and marine fish, but are about 1,000 for molluscs,crustaceans and seaweed.


Tc-99 is a soft beta emitter.

Therefore, external irradiation is not aconsideration.

As Tc-99 distributes relatively uniformlythroughout body tissues, doses to individualorgans and tissues will be of the same order ofmagnitude as average whole-body doses.


The high concentration ratios exhibited bymolluscs, crustaceans and seaweed mean thatthese species should be given specialconsideration.

Lettuce and spinach have also been observed toexhibit particularly high concentration ratios.

T


Name


Parent

Technetium-99m

6.02 hours

Mo-99

Symbol

Principal decaymode

Daughter

Tc-99m

IT

Tc-99 [R]

Origin

Grouping

Detection

Fission

Artificial

In situ


Decay modes


Production • Irradiation of molybdenum with neutrons in a nuclear reactor or cyclotron

Uses• In medicine for diagnostic purposes• Assessing the results of surgery and medical treatment




Speciation

Technetium can exist in a number of oxidationstates, although +7 and +4 are the most stableforms in solution.

In oxidising conditions, the pertechnetate ion(TcO4

-) is the most stable form. It gives rise to saltsthat are stable in the pH range 0 to 14, and whichare generally very soluble.

In reducing conditions, oxides of technetium arethe dominant form of the element.

Analogue species

Technetium exhibits complex chemical,biochemical and biogeochemical interactions.

It is, therefore, strongly recommended thatanalogies be used only with extreme caution whenattempting to characterise the environmentalbehaviour of technetium.

T





Terrestrial

Tc-99m could be stronglyaccumulated in stronglyreducing soils and sediments.

In oxic conditions, however, it islikely to be present as thepertechnetate and to be highlymobile.

In oxic conditions, Tc-99 ishighly available to plants

Aquatic

Tc-99m reacts only weakly withparticulate matter in oxidisingconditions, but can be highlyparticle reactive in reducingconditions.

Discharges to freshwater,estuarine or marineenvironments would beexpected to disperse widely.

Atmospheric

If Tc-99m were released to theatmosphere, it would be as anaerosol.

Environmental sink

The very short half-life meansthat Tc-99m will decay in situ inthe terrestrial environment.

In aquatic environments, it maydisperse a few kilometres beforedecaying in the water column.


The very short half-life of Tc-99m means that it will have littleopportunity to be transferred to terrestrial animals or aquaticorganisms.

However, following a release to air, Tc-99m would be present on thesurfaces of plants and could be subject to some foliar absorption.


Tc-99m is mainly a gamma emitter.

Therefore, external exposure following depositionin a terrestrial environment may be of greatersignificance than internal exposure, given thelimited time for plant or animal uptake.


The high concentration ratios exhibited bymolluscs, crustaceans and seaweed mean thatthese species should be given specialconsideration.

Lettuce and spinach have also been observed toexhibit particularly high concentration ratios.

T


Name


Parent

Thorium-227

18.7 days

Ac-227

Symbol

Principal decaymode

Daughter

Th-227

Alpha

Ra-223 [R]

Origin

Grouping

Detection

Radiogenic

Natural

In situ


Decay modes


Production • From the decay of Ac-227, arising from the decay of U-235

Uses • No specific uses for Th-227

Modes Land• From the decay of naturally occurring U-235 in soils and rocks• Reprocessing of spent fuel

ofAir

• Treatment, reprocessing and disposal of spent fuel• From burning coal

releaseWater • Treatment and disposal of spent fuel

Speciation

The chemistry of thorium is determinedpredominantly by the properties of the +4oxidation state.

Thorium salts tend to hydrolyse in water.

Thorium forms oxide, chloride, nitrate andsulphate compounds, and can also participate inthe formation of organic complexes.

Analogue species

There are similarities between the chemical,biochemical and biogeochemical properties of Thand those of Pu.

However, a considerable amount is known aboutthe environmental behaviour of Th, so it is bestconsidered in its own right.

T





Terrestrial

Thorium is very highly particlereactive in terrestrialenvironments and is stronglyadsorbed to all soil types.

It is very strongly excluded fromplants.

Aquatic

Thorium is very highly particlereactive in aquatic environmentsand may tend to adsorb tosuspended sediments.

It would migrate to bottomsediments by deposition.

Atmospheric

If Th-227 were released to theatmosphere, it would be as anaerosol.

Environmental sink

Th-227 will decay close to itssite of production in terrestrialenvironments.

In aquatic environments, it willeither decay in the watercolumn or in depositedsediments.


Thorium is very strongly excluded from plants.

The main route of intake by animals is likely to be ingestion of soil orsediment.

Thorium is also of very limited bioavailability in animals. Thefractional gastrointestinal absorption is typically <0.1 %.

The Th-227 that does enter the systemic circulation is mainlydeposited in bone, with the liver and kidneys as secondary sites ofdeposition.

It is relatively highly accumulated in aquatic organisms. Thesetypically exhibit concentration ratios relative to water of around1,000 in both freshwater and marine environments.


Th-227 is primarily an alpha emitter.


Therefore, Th-227 is of greatest potentialsignificance when internally incorporated inorgans and tissues that are susceptible to theeffects of alpha radiation.



T


Name


Parent

Thorium-228

1.9 years

Ac-228

Symbol

Principal decaymode

Daughter

Th-228

Alpha

Ra-224 [R]

Origin

Grouping

Detection

Radiogenic

Natural

In situ


Decay modes


Production • From the decay of Ac-228 arising from naturally occurring Th-232


ModesLand • From the decay of naturally occurring Th-232 in soils and rocks

of Air• Treatment and disposal of spent fuel• From burning coal


Speciation




Analogue species



T





Terrestrial



Aquatic

Thorium is very highly particlereactive in aquatic environmentsand would tend to adsorb tosuspended sediments.


Atmospheric


Environmental sink















T


Name


Parent

Thorium-230

7.7 x 104 years

U-234

Symbol

Principal decaymode

Daughter

Th-230

Alpha

Ra-226 [R]

Origin

Grouping

Detection

Radiogenic

Natural

In situ


Decay modes


Production • From the decay of U-234 in nature and in nuclear reactors


ModesLand • From the decay of U-234 in soils and rocks



Speciation




Analogue species



T





Terrestrial



Aquatic



Atmospheric


Environmental sink

The distribution of Th-230 inthe environment will usually besimilar to that of uranium.

However, when Th-230 isproduced from U-234 insolution, e.g. in groundwaters,it will be preferentially lost tosolids by adsorption.

Th-230 originating in, oradsorbed to, solids willgenerally decay in situ.













T


Name


Parent

Thorium-231

25.5 hours

U-235

Symbol

Principal decaymode

Daughter

Th-231

Beta

Pa-231 [R]

Origin

Grouping

Detection

Radiogenic

Natural

In situ


Decay modes


Production • From the decay of U-235


ModesLand • From the decay of U-235 in soils and rocks



Speciation




Analogue species



T





Terrestrial



Aquatic



Atmospheric


Environmental sink










As a short-lived radionuclide emitting primarilylow energy beta particles and gamma rays, Th-231is of little environmental significance in its ownright.

It is mainly of interest as the immediate parent ofPa-231.



T


Name


Parent

Thorium-232

1.41 x 1010 yrs

U-236

Symbol

Principal decaymode

Daughter

Th-232

Alpha

Th-228 [R]

Origin

Grouping

Detection

Primordial

Natural

In situ


Decay modes


Production• Naturally during the formation of the Universe• From the decay of U-236

Uses• Manufacture of gas mantles (Thorium oxide)• As a basis for production of fissionable U-233

ModesLand • From naturally occurring Th-232 in soils and rocks



Speciation




Analogue species



T





Terrestrial



Aquatic



Atmospheric


Environmental sink

Th-232 is widely distributed inthe environment.

However, it is largelyincorporated in minerals andtends to be very immobile.













T


Name


Parent

Thorium-234

24.1 days

U-238

Symbol

Principal decaymode

Daughter

Th-234

Beta

Pa-234m [R]

Origin

Grouping

Detection

Radiogenic

Natural

In situ


Decay modes


Production • From the decay of U-238


Modes Land• Disposed uranium mill tailings and debris• From naturally occurring U-238 in soil and rocks

ofAir

• Treatment and disposal of spent fuel• From burning coal


Speciation




Analogue species



T





Terrestrial



Aquatic



Atmospheric


Environmental sink

The distribution of Th-234 inthe environment will usually besimilar to that of U-238.

However, when Th-230 isproduced from U-234 insolution, e.g. in groundwaters,it will be preferentially lost tosolids by adsorption.

Th-234 originating in, oradsorbed to, solids willgenerally decay in situ.








Th-234 is a short-lived beta-gamma emitter.

It is of little dosimetric significance compared withits progeny, notably U-234.



T


Name


Parent

Thallium-201

3.04 days

N/A

Symbol

Principal decaymode

Daughter

Tl-201

EC

Hg-201

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes



Uses • Sometimes used in medical research and diagnostics

Modes Land• Sewage sludge application to land, but would probably decay substantially




Speciation

Thallium is a Group III element whose dominantoxidation states are +1 and +3.

Both states can form oxides, nitrates, sulphatesand halides.

The +3 oxidation state can readily formcomplexes.

Analogue species

Biochemically, Tl mimics K, which it resembles insize and ionic charge.

In mammals, it is an insidious poison because itaffects K-activated enzymes in the brain, musclesand skin.

T





Terrestrial

Tl-201 is likely to bind stronglyto the clay fraction of soils.However, because of its shorthalf-life, it is likely to be mainlyof interest in terms of foliardeposition.

Aquatic

By analogy with K, Tl-201would be expected to be readilyavailable to aquatic organisms.

Atmospheric

If Tl-201 were released toatmosphere, it would be as anaerosol.

Environmental sink

Tl-201 in the terrestrialenvironment is likely to decay insitu.

Dispersion in aquaticenvironments will be limited byits short half-life and it willdecay mainly in the watercolumn


Some uptake of foliar-deposited Tl-201 may occur, but this has notbeen measured.

Tl-201 is highly bioavailable to animals.

It is completely absorbed from the gastrointestinal tract in mammalsand becomes relatively uniformly distributed throughout the body.

It is likely to be concentrated in the muscle of freshwater fish.


Tl-201 is primarily a gamma-emitting radionuclide.

Because of its short half-life, external irradiation interrestrial environments may be more importantthan internal irradiation.



T


Name


Parent

Total alpha

Various

Various

Symbol

Principal decaymode

Daughter

Total alpha

Various

Various

Origin

Grouping

Detection

Various

Various

Various






Production• Neutron irradiation of uranium and plutonium (post-actinides)• Decay of post-actinides or naturally occurring isotopes

Uses • Various

Modes Land • Various, e.g. treatment of spent fuel

of Air • Various, e.g. treatment of spent fuel

release Water • Various, e.g. treatment of spent fuel

Speciation

The compounds formed by the different types ofalpha emitter will depend on the species underconsideration. More information can be foundunder the individual radionuclide entries.

Analogue species

Alpha emitters arise mainly in the actinide series,so they exhibit a number of chemical similarities toeach other. However, the range of elements(including Po, Rn, Ra, Th, U, Np, Pu, Am and Cm)is too wide for any general statement to be madeconcerning analogues.

The behaviour of alpha emitters in the environment is most appropriately discussed in the context ofindividual radioisotopes of Po, Rn, Ra, Th, U, Np, Pu, Am and Cm.

Environmental sink

As above


As above. Also, most alpha emitters exhibit low bioavailability in bothterrestrial plants and animals. However, alpha emitters oftenaccumulate strongly in marine invertebrates and seaweed.



Unless alpha emitters also emit substantialamounts of gamma radiation, which is unusual,they are almost exclusively of relevance in thecontext of internal irradiation.


As above

T



Name


Parent

Total beta

Various

Various

Symbol

Principal decaymode

Daughter

Total beta

Various

Various

Origin

Grouping

Detection

Various

Various

Various






Production • Various, e.g. activation and fission

Uses • Various, including medical and engineering applications

Modes Land • Various

of Air • Various

release Water • Various

Speciation

The compounds formed by the different types ofbeta emitter will depend on the species underconsideration. More information can be foundunder the individual radionuclide entries.

Analogue species

Beta emitters comprise radioisotopes of elementswith a very wide range of chemical, biochemicaland geochemical characteristics. Therefore, nogeneralisations can be made.

Environmental sink

See above


See above



See above. It should be remembered that manybeta emitters are also strong gamma emitters.


See above

T

In some circumstances, enquiry can establish that total beta actually relates to a limited number ofradionuclides. If this is the case, reference can be made to radionuclide-specific datasheets. The generalcategory of total beta without further characterisation is of little utility.



Name


Parent

Uranium-234

2.45 x 105 yrs

Pa-234m,Pu-238

Symbol

Principal decaymode

Daughter

U-234

Alpha

Th-230 [R]

Origin

Grouping

Detection

Primordial

Natural

In situ


Decay modes


Production• From the decay of Pu-238• From the decay of Pa-234m in the U-238 chain

Uses • Mainly for research purposes

Modes Land• Disposed uranium mill tailings and debris;• From naturally occurring U-234 in soil and rocks• Treatment, reprocessing and disposal of spent fuel

ofAir


releaseWater • Treatment, reprocessing and disposal of spent fuel

Speciation


Uranium forms a wide range of halide and oxidecompounds.

The hydroxide and carbonate are also known anduranium can participate in the formation oforganic complexes.

Analogue species

The chemical, biochemical and biogeochemicalproperties of uranium are quite distinct from thoseof the other actinide elements and there is a greatdeal of information on its environmentalbehaviour.

For this reason, there is no requirement to identifyanalogue elements.

U





Terrestrial



In general, it is stronglyexcluded from plants

Aquatic



Atmospheric


Chemical forms could includeUO2, U3O8 and UF4. In addition,the toxic gas UF6 could bereleased.

Environmental sink

U-234 is produced in theenvironment from U-238.Almost all of this uraniumremains at its site of productionuntil it decays.

However, U-234 entering theenvironment due to humanactivities may be more mobile,migrating with groundwatersand surface waters until itreaches the aqueousenvironment.


In general, uranium is strongly excluded from plants, although cerealcrops can show a degree of accumulation of uranium.

Uranium is not very bioavailable to animals. The fractionalgastrointestinal absorption is typically 1%-2 %. Mineral bone is theprincipal site of accumulation.



U-234 is primarily an alpha emitter.


Therefore, U-234 is of greatest potentialsignificance when internally incorporated inorgans and tissues that are susceptible to theeffects of alpha radiation.

Note that uranium is chemically toxic as well asposing a radiation hazard.



U


Name


Parent

Uranium-235

7.04 x 108 yrs

Pu-239

Symbol

Principal decaymode

Daughter

U-235

Alpha

Th-231 [R]

Origin

Grouping

Detection

Primordial

Natural

In situ


Decay modes


Production • Naturally during the formation of the Universe

Uses • As a basic fuel for nuclear fission reactors

ModesLand • Treatment and disposal of spent fuel



Speciation




Analogue species



U





Terrestrial



Aquatic



Atmospheric



Environmental sink

U-235 is a primordialradionuclide widely distributedin rocks, soils and sediments.

As it is incorporated in themineral phase, it tends toremain in situ.

U-235 entering theenvironment due to humanactivities may be more mobile.












U


Name


Parent

Uranium-238

4.47 x 1010 yrs

Pu-242

Symbol

Principal decaymode

Daughter

U-238

Alpha

Th-234 [R]

Origin

Grouping

Detection

Natural

Primordial

In situ


Decay modes


Production • Naturally during the formation of the Universe

Uses• As the starting point for production of Pu-239• For the production of armour-piercing munitions

Modes Land• Disposed uranium mill tailings and debris• From naturally occurring U-238 in soil and rocks• Treatment, reprocessing and disposal of spent fuel

ofAir


releaseWater • Treatment, reprocessing and disposal of spent fuel

Speciation




Analogue species



U





Terrestrial



In general, it is stronglyexcluded from plants

Aquatic



Atmospheric



Environmental sink

U-238 is a primordialradionuclide widely distributedin rocks, soils and sediments.

As it is incorporated in themineral phase, it tends toremain in situ.

U-238 entering theenvironment due to humanactivities may be more mobile.












U


Name


Parent

Vanadium-48

16.2 days

N/A

Symbol

Principal decaymode

Daughter

V-48

EC

Ti-48

Origin

Grouping

Detection

Activation

Artificial

In situ


Decay modes


Production • Irradiation of non-radioactive precursors in a cyclotron or nuclear reactor

Uses• Certain medical applications, for example delivering radiation doses to arteries

inside a stent (mesh container)




Speciation

Vanadium is a transition metal that can showoxidation states from -1 through to +5.

It forms sulphate, oxide and halide compounds.

Because of the ability to hold different oxidationstates, there are several different forms ofsulphate, oxide and halide compounds.

Analogue species

There have been extensive studies on thedistribution and transport of vanadium in theenvironment.

Therefore, it is not appropriate to identify anyanalogues.

V





Terrestrial

Relative to other metals, V isfairly mobile in neutral oralkaline soils, but its mobility islower in acid soils.

Mobility is much higher inoxidising than in reducingconditions.

Aquatic

In freshwater, V-48 is likely to bepresent as V4+ under reducingconditions and V5+ underoxidising conditions.

Both species are known to bindstrongly to mineral or biogenicsurfaces.

In the oceans, most V isremoved from the water columnby deposition.

Atmospheric

If V-48 is released toatmosphere, it will be in theform of an aerosol.

Environmental sink

Because of its short half-life, V-48 in terrestrial environmentsis likely to decay in situ.

In aquatic systems, V-48 willdecay both in the water columnand in deposited sediments.


V-48 in the terrestrial environment is likely to be present mainly onthe external surfaces of plants following deposition from theatmosphere.

Vanadium is of limited bioavailability to animals and the fractionalgastrointestinal absorption is ~1 %.

Vanadium entering the systemic circulation is preferentially depositedin the skeleton of mammals.

Marine plants and invertebrates contain higher concentrations ofvanadium than terrestrial plants and animals.


V-48 emits energetic gamma rays.

Because of its short half-life and limitedbioavailability to many plants and animals interrestrial environments, external irradiation maybe of greater significance than internal irradiation.

Similarly, external irradiation from materialadsorbed to external surfaces of organisms may beimportant in the aquatic environment.


There are specific species of higher plants andfungi that accumulate stable V. These may alsoaccumulate V-48.

V


Name


Parent

Xenon-133

5.2 days

N/A

Symbol

Principal decaymode

Daughter

Xe-133

Beta

Cs-133

Origin

Grouping

Detection

Fission

Artificial

Laboratory


Decay modes



Uses • Occasionally used in medicine for diagnostic imaging




Speciation

Xenon is a noble gas and, as such, forms only alimited number of chemical compounds due to itslack of reactivity.

One such example is XeF2.

Analogue species



Rn is therefore not an appropriate analogue for Xe.

X





Terrestrial

Xe-133 is not transferredsignificantly to the terrestrialenvironment.

Aquatic

Xe-133 is not transferredsignificantly to the aquaticenvironment.

Atmospheric

Xe-133 is almost exclusivelyreleased to the atmosphere.

Its short radioactive half-life andlow reactivity means that itdecays almost entirely duringatmospheric transport and is nottransferred significantly to otherenvironmental media.

Environmental sink

No major sink, owing to its lackof reactivity and short half-life.


Xe-133 is sparingly soluble in body tissues, notably those with a highfat content. However, it is not metabolised.

Some Xe-133 will be present in the lungs in inhaled air.


Xe-133 emits beta particles and low energygamma rays.

Radiation doses to organisms arise mainly due toexternal beta and gamma irradiation, irradiation ofthe lungs of animals from contained gas andinternal irradiation from gas dissolved in tissues.


Because Xe-133 is not metabolised to anysignificant degree, there are no major species-dependent considerations.

X


Name


Parent

Yttrium-90

64 hours

Sr-90

Symbol

Principal decaymode

Daughter

Y-90

Beta

Zr-90

Origin

Grouping

Detection

Radiogenic

Artificial

Laboratory


Decay modes


Production• Produced during fission in a nuclear reactor• From decay of strontium-90, another important fission isotope

Uses • In medicine for the treatment of cancer and arthritis




Speciation

Yttrium is a transition metal that only formscompounds in the +3 oxidation state.

The chemistry of yttrium is very similar to that ofthe rare earths.

As such, yttrium forms compounds withhydrogen, oxygen and the halides. It also forms anumber of stable complexes.

Analogue species

Ce is the most studied of the rare earths andprovides a good analogue for the behaviour of Y-90.

However, in the environment, Y-90 is usuallypresent as a result of the decay of Sr-90 and itsbehaviour is often determined by that of itsparent.

Y





Terrestrial

Y-90 is highly particle reactiveand would tend to bind tosurfaces when produced.

Aquatic

In aquatic environments, Y-90produced from Sr-90 wouldtend to be particle reactive andwould, therefore, tend tomigrate from the water columnby deposition

Atmospheric

If Y-90 were released to theatmosphere, it would be in theform of an aerosol.

Environmental sink

In general, the short half-lifeand limited mobility of Y-90 willmean that it decays close to itspoint of production.


In plants and animals, Y-90 is likely to be present in concentrationsthat are close to secular equilibrium with those of Sr-90.

With the assumption of secular equilibrium, intake and uptake routesfor Y-90 are of limited importance.

As with Sr-90, high concentrations are likely to be found in theskeleton.


Y-90 is a pure beta emitter.

Under the assumption of secular equilibrium, aconvenient approach to dosimetry is to assign theY-90 beta energy to its parent Sr-90.


As for Sr-90

Y


Name


Parent

Zirconium-95

64 days

N/A

Symbol

Principal decaymode

Daughter

Zr-95

Beta [gamma]

Nb-95 [R]

Origin

Grouping

Detection

Fission

Artificial

In situ


Decay modes


Production• Produced during fission in a nuclear reactor• Irradiation of zirconium cladding with neutrons in a nuclear reactor

Uses • No specific uses outsides research activities

ModesLand • During treatment and disposal of spent fuel

ofAir • During treatment and disposal of spent fuel

release Water• During treatment and disposal of spent fuel• Liquid discharges from nuclear facilities

Speciation

The most important oxidation state for zirconiumin aqueous solution is +4.

However, the Zr4+ ion is only soluble in strong(laboratory) acid solutions (pH <1).

In water, zirconium hydrolyses very easily to formhydroxo complexes, unless in the form of the verystable fluoride.

Analogue species

There are chemical, biochemical andbiogeochemical similarities between Zr and Nb.

However, both elements have been studied to asimilar degree and there is little merit in treatingZr as an analogue of Nb or vice versa.

Z





Terrestrial

Zr-95 is highly particle reactive.

It will therefore tend to remainin situ, rather than migratingthrough the terrestrialenvironment in surface orgroundwaters.

Aquatic

Zr-95 is highly particle reactivein marine systems.

In freshwater systems, it hasmoderate to high particlereactivity.

However, even in marinesystems, a significant fraction ofthe Zr-95 may be associatedwith colloids or dissolvedorganic matter complexes.

Atmospheric

If Zr-95 were released to theatmosphere, it would disperse asan aerosol.

Environmental sink

Zr-95 will generally decay closeto its point of deposition in theterrestrial environment.

In aquatic systems, Zr-95 willinteract with mineral sediments,colloids and dissolved organicmatter.

Some will be transferred tobottom sediments and decaywill occur there or in the watercolumn.


Zr-95 is strongly excluded from plants.

It is also not very bioavailable to animals, with a fractionalgastrointestinal absorption of ~0.2 %, although this may beincreased in pre-weaned juveniles.

Zr-95 that enters systemic circulation is widely dispersed in softtissues, but the main reservoir of uptake and long-term retention ismineral bone.

Concentration ratios relative to water are about 20 for freshwaterand marine fish, but can be >1,000 for marine invertebrates andseaweed.


Zr-95 has a high yield of energetic gamma rays.

Because of its low bioavailability in terrestrialenvironments, external irradiation is likely to be ofgreater significance than internal irradiation.

External irradiation may also be of greatestimportance in the aquatic environment.


The main species-specific consideration is thepartitioning of Zr-95 in marine invertebratesbetween adsorbed, unassimilated particulate andtissue uptake fractions.

Z

Glossary

This glossary defines some of the terms used in thispublication, but also replicates entries from theglossary found in Copplestone et al. (2001). Othersources, e.g. IAEA (2000), provide a more extensivelist of definitions.

AberrationDeparture from normal.

Absorbed doseQuantity of energy imparted by ionising radiationto unit mass of matter such as tissue. Unit Gray,symbol Gy. 1Gy = 1 joule per kilogram.

ActinidesA group of 15 elements with atomic number fromthat of actinum (89) to lawrencium (103) inclusiveand analogous to the so-called lanthanide series ofrare earth metals. All are radioactive. In general,the actinides are highly particle reactive and arenot taken up easily by plants or animals.Nevertheless, they are generally very radiotoxic.

ActivationThe process in which non-radioactive elements areconverted to radioactive elements as a result ofexposure to radiation in a nuclear reactor orweapon explosion. An example is the formation oftechetium-99m for medical purposes fromirradiation of molydenum-99.

ActivityAttribute of an amount of a radionuclide.Describes the rate at which transformations occurin it. Unit Becquerel, symbol Bq. 1Bq = 1 transformation per second.

Acute exposureExposure received within a short period of time.Normally used to refer to exposure of sufficientlyshort duration that the resulting dose can betreated as instantaneous (e.g. less than an hour).Usually contrasted with chronic and transitoryexposure.

AdsorbUsually a solid holding molecules (of a gas orliquid, etc.) to its surface, forming a thin film.


Advanced gas cooled reactorA development of the Magnox reactor, usingenriched uranium oxide fuel in stainless steelcladding.

AerosolA suspension of fine solid or liquid particles in gas.Smoke, fog, and mist are examples of aerosols.

Alpha particleA particle consisting of two protons plus twoneutrons, i.e. fast-moving helium nuclei (atomicmass of 4 and atomic number 2). Emitted by aradionuclide.

AllotropyThe ability of certain elements and compounds(e.g. phosphorus) to show two or more distinctphysical forms in the same physical state (e.g.solid).

AntineutrinoA particle without mass or charge that is emittedfrom the nucleus, along with an electron, duringbeta decay.

ApoptosisApoptosis or programmed cell death occursnaturally during the development andmaintenance of animal tissues and organs. Duringthese processes, more cells are produced than arerequired for building tissues and organs. Theunwanted cells are programmed to die eitherbecause the chemical signals that direct them togo on living are suppressed or because they receivea specific signal to die.

AtomThe smallest portion of an element that cancombine chemically with other atoms.

Atomic massThe mass of an atomic nucleus, usually denoted bythe symbol A.

Atomic numberThe number of protons within an atomic nucleus,usually denoted by the symbol Z.

Auger electronA low-energy electron ejected from an atomfollowing the transition of another electron from ahigher to lower energy state.

AuthorisationThe granting by a regulatory body or othergovernmental body of written permission for anoperator to perform specified activities.

BackgroundThe dose or dose rate (or an observed measurerelated to the dose or dose rate), attributable to allsources other than the one(s) specified.

Becquerel (Bq)See activity.

Benthic invertebrateAquatic invertebrate living on or in sediment.

BenthosSynonym for community of benthic invertebrate.

Beta particleA negatively charged (electron) or positivelycharged (positron) particle emitted from thenucleus of an atom during radioactive decay.Often loosely assumed to be the negativelycharged particle.

BioavailabilityThe degree and rate at which a substance isabsorbed into a living system or is made availableat the site of physiological activity.

BiomarkerA biological response to an environmentalpollutant, which gives a measure of exposure. Theresponse may be molecular, cellular or wholeorganism.

BiotaA collective term for the flora and fauna.

Breeding (in radiation term)The production of one radionuclide from anotherdue to the action of incident atomic particles, e.g.the production of plutonium-239 from uranium-238.

ChromatidWhen a chromosome becomes shorter and thickerduring the first stage of mitosis it is seen tobecome a double thread. Each thread is achromatid.


Chromosome translocationSporadic and random fusion of part of onechromosome onto part of another.

ChromosomesRod-shaped bodies found in the nucleus of cells inthe body. They contain the genes or hereditaryconstituents. Each chromosome has acharacteristic length and banding pattern.

Chronic exposureExposure persisting in time. Normally used to referto continuous exposures to low concentrations ofpollutants. See also transitory and acute exposure.

Concentration factor (CF)Ratio of element or nuclide in the consumer (or aspecific tissue or organ etc.), to that in what isconsumed, or to that in the environmentalmedium.

Cosmic radiationHigh energy ionising radiation from outer space.

CosmogenicDenoting radionuclides produced in the upperatmosphere due to the action of cosmic rays.

Critical groupSub-group of the public most affected by a givenrelease of radioactivity.

Critical organThe organ or tissue the irradiation of whichpresents the greatest threat to the health of theindividual.

Critical pathwayThe pathway that leads to the greatest dose ofradiation. An example would be the air-grass-cow-milk pathway, important for iodine isotopesreleased into the air.

CyclotronAn apparatus for producing high-energy atomicparticles.

Cytogenetic damageDamage to chromosomes that can be detected onthe microscopic level. Examples of damageinclude deletions, translocations and micronuclei.

DecayThe process of spontaneous transformation of aradionuclide. The decrease in the activity of aradioactive substance.

Decay productA nuclide or radionuclide produced by decay. Itmay be formed directly from a radionuclide or as aresult of a series of successive decays throughseveral radionuclides.

DecommissioningThe process of closing down a nuclear reactor,removing the spent fuel, dismantling some of theother components, and preparing them fordisposal. Term may also be applied to other majornuclear facilities.

DepositionThe settling of particles from the atmosphere tothe ground or plant surfaces. Deposition can bewet (e.g. through rainfall) or dry.

Deterministic effectA radiation effect for which generally a thresholdlevel of dose exists above which the severity of theeffect is greater for a higher dose.

DisposalIn relation to radioactive waste, dispersal oremplacement in any medium without the intentionof retrieval.

DNADeoxyribonucleic acid. The compound thatcontrols the structure and function of cells and isthe material of inheritance.

DoseGeneral term for quantity of ionising radiation.See absorbed dose, equivalent dose and effectivedose. Frequently used for effective dose.

Dose assessmentAssessment of the dose(s) to an individual or groupof people.

Dose rateDose released over a specified unit of time.

Effective doseThe quantity obtained by multiplying theequivalent dose to various tissues and organs by aweighting factor appropriate to each and summingthe products. Unit Sievert, symbol Sv. Frequentlyabbreviated to dose.

Electromagnetic radiationRadiation consisting of electric and magnetic wavesthat travel at the speed of light. Examples: light,radio waves, gamma rays, x-rays.


ElectronThe electron is a small atomic particle with 1 unitof negative electric charge and a mass of 1/1836 of aproton. Every atom consists of one nucleus andone or more electrons in orbit around the nucleus.Positively charged electrons, called positrons, alsoexist. See also beta particle.

Electron capture (EC)A form of radioactive decay in which the nucleuscaptures an orbiting electron, converting a protonto a neutron, the energy being released as X-rays(or Auger electrons).

Electron voltUnit of energy employed in radiation physics.Equal to the energy gained by an electron inpassing through a potential difference of 1 volt.Symbol eV. 1eV = ~1.6 x 10-19 joule.

Embryo (in animals)The stage of development between the time thatthe fertilised egg begins to divide and thedeveloping animal hatches or is born.

Embryo (in plants)The part of a seed which develops into the root(radicle) and shoot (plumule) of a plant.

EmbryogenesisThe processes leading to the development of anembryo.

Endpoint1. The final stage of a process, especially the pointat which an effect is observed.2. A radiological or other measure of protection orsafety that is the calculated result of an analysis orassessment.

Enriched uraniumUranium in which the content of the isotopeuranium-235 has been increased above its naturalvalue of 0.7 % by weight.

Equivalent doseThe quantity obtained by multiplying the absorbeddose by a weighting factor (radiation weightingfactor) to allow for the different effectiveness of thevarious ionising radiation in causing harm to tissue.Unit Sievert, symbol Sv.

FalloutThe transfer of radionuclides produced by nuclearweapons from the atmosphere to earth; thematerial transferred.

FecundityThe number of viable offspring produced by anorganism; mature seeds produced, eggs laid, orlive offspring delivered, excluding fertilisedembryos that have failed to develop.

FertilityIn sexually reproducing plants and animals, it is thenumber of fertilised eggs produced in a given time.

FissionNuclear fission. A process in which a nucleus splitsinto two or more nuclei and energy is released.Frequently refers to the splitting of a nucleus ofuranium-235 into two approximately equal partsby a thermal neutron with emission of one or moreneutrons and the release of energy.

Fission productsThe atoms formed as a result of nuclear fission, e.g.caesium-137, iodine-131, strontium-90, cerium-144.

FoetusThe developing embryo is known as a foetus onceit can be recognised as a species.

Free radicalA grouping of atoms that normally exists incombination with other atoms but can sometimesexist independently. Generally very reactive in achemical sense.

GametesThe sex cells which fuse together at fertilisation toform the zygote. In animals, the gametes are thesperm in males and the ovum (egg) in females. Inplants, the gametes are the pollen in the male andthe ovules in the female.

GametogenesisProcess leading to the production of gametes.

Gamma radiationVery penetrating electromagnetic radiation,without mass or charge, frequently emitted fromthe nucleus of an atom during radioactive decay.Emitted by a radionuclide.

GenesThe biological units of heredity. They are arrangedalong the length of chromosomes.

GenotoxicityAbility to cause damage to genetic material. Suchdamage may be mutagenic and/or carcinogenic.


Germ cellCell specialised to produce gametes. The germ cellline is often formed very early in embryonicdevelopment.

GestationThe process of being carried in the womb, fromconception to birth.

Gray (Gy)See absorbed dose.

High level waste (HLW)The radioactive liquid containing most of thefission products and actinides present in spent fuel,which forms the residue from the first solventextraction cycle in reprocessing, and some of theassociated waste streams. The term is also usedfor: this material following solidification; spent fuel(if it is declared a waste); or any other waste withsimilar radiological characteristics.

ImplantationWhen an embryo passes from the oviduct to theuterus, it becomes attached to the uterine wall.

Indicator speciesA species that only thrives under certainenvironmental conditions and whose presenceshows that these conditions are present.

Inert gasA member of the family of gaseous chemicalelements characterised by their extreme lack ofreactivity. The inert gases are: helium, neon,argon, krypton, xenon and radon.

IonAn atom or group of atoms that carries a netelectrical charge - either positive or negative.

IonisationThe process by which a neutral atom or moleculeacquires or loses an electric charge. Theproduction of ions.

Ionising radiationRadiation that produces ionisation in matter.Examples are alpha particles, gamma rays, X-raysand neutrons. When these pass through thetissues of the body, they have sufficient energy todamage DNA.

IrradiationExposed to radiation.

Isomeric transformation (IT)A form of radioactive decay in which a metastablenucleus decays with the release of energy asgamma rays.

IsomersIn this context, nuclides having the same numberof protons and neutrons in their nucleus but indifferent energy states.

IsotopeNuclides with the same number of protons butdifferent numbers of neutrons. Not a synonym fornuclide.

KaryotypeThe complete set of chromosomes of a cell ororganism.

LanthanidesThe group of elements with atomic numbersbetween Z = 57 and Z = 70. They have similarchemical properties and are highly particlereactive.

LD50

The dose that causes mortality in 50 % of theorganisms tested.

Linear energy transfer (LET)A measure of how, as a function of distance,energy is transferred from radiation to the exposedmatter. Radiation with high LET is normallyassumed to comprise of protons, neutrons andalpha particles (or other particles of similar orgreater mass). Radiation with low LET is assumedto comprise of photons (including X-rays andgamma rays), electrons and positrons.

Low and intermediate level waste (LLW and ILW)Radioactive waste with radiological characteristicsbetween those of exempt waste and high levelwaste. These may be long-lived waste (LILW-LL) orshort-lived waste (LILW-SL).

Magnox reactorA thermal reactor named after the magnesiumalloy in which the uranium metal fuel is contained.The moderator is graphite and the coolant iscarbon dioxide gas.

MeiosisA form of nuclear division in which each daughtercell receives only one of each homologouschromosome pair. Meiosis occurs during theformation of gametes.


MetabolismThe chemical changes in living cells by whichenergy is provided for vital processes and activitiesand new material is assimilated.

MitosisA type of cell division by which two daughter cellsare produced from one parent cell, with no changein the number of chromosomes.

ModeratorA material used in nuclear reactors to reduce theenergy and speed of the neutrons produced as aresult of fission.

MoleculeThe smallest portion of a substance that can existby itself and retain the properties of the substance.

MorbidityThe state of being diseased.

MorphogenesisThe process of ëshape formationí: the processesthat are responsible for producing the complexshapes of adults from the simple ball of cells thatderives from division of the fertilised egg.

MutationA change in the genetic material of an organism.This can be spontaneous or induced by chemicalsor radiation.

Naturally occurring radionuclidesRadionuclides that occur naturally in significantquantities on Earth.

NeutrinoA particle without mass or charge that is emittedfrom the nucleus, along with a positron, duringbeta decay.

NeutronA fundamental nuclear particle of mass 1 and zeroelectric charge.

Non-ionising radiationRadiation that does not produce ionisation inmatter. Examples are ultraviolet radiation, light,infrared radiation and radio-frequency radiation.When these radiation pass through the tissues ofthe body, they do not have sufficient energy todamage DNA directly.

Non-nuclear licensed siteA non-nuclear licensed site (or non-nuclear site) iswhere the handling, use and discharge ofradioactive substances may occur but not as themain activity. This includes research institutions,hospitals, defence establishments, etc.

Nuclear fuel cycleThe stages in which the fuel for nuclear reactors isfirst prepared, then used, and later reprocessed forpossible use again. Waste management is alsoconsidered part of the cycle.

Nuclear licensed siteA nuclear licensed site (or nuclear site) holds anoperating licence under the Nuclear InstallationsAct 1965; the handling or use of radioactivematerials is the main activity.

Nuclear powerPower obtained from the operation of a nuclearreactor.

Nuclear reactorA device in which nuclear fission can be sustainedin a self-supporting chain reaction involvingneutrons. In thermal reactors, fission is broughtabout by thermal neutrons.

Nuclear weaponExplosive device deriving its power from fission orfusion of nuclei or from both.

Nucleus (of atom)The core of an atom, occupying little of thevolume, containing most of the mass, and bearingpositive electric charge.

Nucleus (of cell)The central part of a cell containing chromosomesand the genetic information bound in DNA.

NuclideA species of atom distinguished by its particularnumber of protons and number of neutrons.

OocyteThe developing female gamete before maturationand release.

OrganogenesisThe process of formation of specific organs in aplant or animal involving morphogenesis anddifferentiation.


OrganometallicAn organic compound that contains a metal ormetalloid element bonded directly to carbon.

Oxidation numberThe number of electrons that must be added to apositive ion, or removed from a negative ion, toproduce a neutral atom. Thus, for example, forvanadium in an oxidation state of +5, five electronsmust be added to produce neutral vanadium.

Pelagic biotaAquatic organisms living in the water column of abody of water, rather than along the shore or inthe bottom sediments.

PhotonA quantum of electromagnetic radiation.

PhotosynthesisThe formation of carbohydrates from carbondioxide and a source of hydrogen (e.g. water) inthe chlorophyll-containing tissues of plantsexposed to light.

PositronA positively charged beta+ particle. Positronsrapidly interact with negatively charged electrons,releasing two gamma ray photons.

Pressurised water reactor (PWR)A thermal reactor using water as both a moderatorand coolant. Uses enriched uranium oxide fuel.

Primordial radionuclidesRadionuclides left over from the creation of theuniverse. They necessarily have very long half-lives, e.g. uranium-238 and thorium-232.

ProgenyAtomic nuclei produced from the radioactive decayof parent nuclei. Same as ëdaughtersí.

ProtonA fundamental nuclear particle with mass of1.672614 x 10-27 kg and positive electric charge of1. The proton is in effect a hydrogen nucleus.

RadiationThe emission and propagation of energy throughspace or through a material medium in the form ofwaves. The term may be extended to includestreams of sub-atomic particles such as alpha andbeta particles as well as electromagnetic radiation.Frequently used for ionising radiation, except whenit is necessary to avoid confusion with non-ionisingradiation.

Radiation weighting factor (wr)wr values (radiation weighting factors) representthe relative biological effectiveness of the differentradiation types, relative to X- or gamma rays, inproducing endpoints of ecological significance.

RadioactiveThe term used to describe an element thatundergoes radioactive decay.

Radioactive half-lifeThe time taken for half of the atoms of aradioactive element to decay. Each radioisotopehas a unique half-life. The half-life is a constantwhich is unaffected by any physical conditionssuch as temperature or pressure. Symbol T1/2.

Radioactive wasteUseless material containing radionuclides.Frequently categorised in the nuclear powerindustry according to activity and other criteria, aslow level, intermediate level, and high level waste.

RadiobiologyThe study of the effects of ionising radiation onliving things.

RadiogenicA term applied to radionuclides that arise from thedecay of other radionuclides.

Radiological protectionThe science and practice of limiting the harm tohuman beings from radiation.

RadionuclideAn unstable nuclide that emits ionising radiation.

Regulatory bodyAn authority or a system of authorities designatedby the government of a state as having legalauthority for conducting the regulatory process,including issuing authorisations and therebyregulating nuclear processes, radiation, radioactivewaste and transport safety.


Relative Biological Effectiveness (RBE)A relative measure of the effectiveness of differentradiation types at inducing a specified healtheffect, expressed as the inverse ratio of theabsorbed doses of two different radiation typesthat would produce the same degree of a definedbiological endpoint.

ReprocessingA process or operation, the purpose of which is toextract radioactive isotopes from spent fuel forfurther use.

RespirationThe process by which organic compounds ofcarbon in plant and animal tissue are broken downto carbon dioxide and water, at the same timereleasing energy.

RiskA measure of the probability and extent of harm.

SievertSee effective dose.

Somatic cellsSoma, from the Greek meaning body. All bodycells except the gametes and the cells from whichthe gametes develop.

Spent fuelNuclear fuel removed from a reactor followingirradiation, which is no longer useable in itspresent form because of depletion of fissilematerial, poison build-up or radiation damage.

SpermatocytesCells of the male reproductive system.

Stem cellA cell that upon division produces dissimilardaughters, one replacing the original stem cell, theother differentiating further (e.g. meristems ofplants).

Stochastic effectA radiation-induced health effect, the probability ofoccurrence of which is greater for a higherradiation dose and the severity of, which (if itoccurs) is independent of dose.

Taxon (taxa)A member of a formal classification of plants andanimals according to their presumed naturalrelationships.

TelomereThe end of a chromosome.

Transitory exposureExposure that is too protracted to be described asacute exposure, but does not persist for manyyears, is sometimes described as transitoryexposure.

Transuranic elementElements of atomic number greater than that ofuranium (atomic number 92). Examples areneptunium, plutonium, curium and americium

Wash-offThe removal of radionuclides from plant surfaces tothe ground through the action of precipitation.

X-rayA discrete quantity of electromagnetic energywithout mass or charge, with less energy thangamma rays. They can be produced by the actionof an electron beam on a metal target. They areemitted by some processes in radioactive decay.


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