Health, Safety and Environmentwww.hse.ubc.ca

Radiation Basics 101

Atomic Structure

Nuclear Formula

A 29-38 X SulphurZ 16

A = Mass Number (P+N)

Z = Atomic Number (P)

Hydrogen - +

Deuterium - +

Tritium - +

XA

ZH

11

H1

2

H1

3

_

Nuclear Stability• Stability related to the ratio of protons to

neutrons:Name: Protons / Neutrons Stability

Hydrogen 1/0

Deuterium 1/1

Tritium 1/2

Carbon-12 6/6

Carbon-13 6/7

Caron-14 6/8

Radioactivity

Spontaneous nuclear transformationsthat result in the formation of atoms

of a different element.During the decay process

energy and/or particles are emittedthat are capable of ionizing matter

Radioactive Decay• Unstable isotopes undergo a spontaneous

decay of the nucleus which improves proton to neutron ratio = more stable

• Particle decay:

• Alpha (α++)

• Beta (β-)

• Positron (β+)

• Electron Capture

Alpha Decay

• Nuclear Fragment ~ Helium nucleus

• 2 Protons and 2 Neutrons

A A-4

X Y + ++

Z Z-2

Alpha Decay

• External Exposure:Not significant hazard

• Internal Exposure:Very hazardous- highly ionizing

e.g. Polonium 210

AlexanderLitvinenko

Polonium 210poisoning

Ingested 2GBq(50 mCi ~10ug)

~200x med. lethal dose

(Click on photo for story)

(November 2006)

238 Pu Uranium 94 234 U + ++

92

Alpha Decay

Plutonium

e.g. Plutonium 238

Click on photo for a video on alpha decay

Beta Decay

• Negative Electron• Very Small Mass

A A

X Y + ß-

Z Z+1

32 P -15 32 S 16 14 C - 6 14 N 7

1.71 MeV

0.156 MeV

Max. Energy

eg. Cl-36

Beta Decay

Beta Decay• A.K.A:

Click on photo for a video on beta decay

Beta Decay Internal Exposure:

Can result in high internal exposure depending on isotope and activity

External Exposure: Can give high dose to skin : erythemaCan damage eyesSecondary radiations can be penetrating

Bremsstrahlung

Bremsstrahlung

Produces X-rays

Dental X-ray Unit

Inside a Dental X-Ray Tube

Positron Decay

Positive ElectronSame mass as negative electronAnnihilation radiation 511 keV

Positron DecayA A

X Y + ß+

Z Z-1

22

Na ß+ 22

11 Ne 10

ßß--511 keV511 keV

*

Positron Decay

• Positrons are not hazardous

– Immediately disappear upon emission. The secondary x-ray ‘annihilation radiations’ are hazardous.

•Internal Exposure:–Can result in high internal dose.

•External Exposure: –Can give equally high dose to skin and deep body core.

PET Scan

Electron Capture

Electron falls into nucleus + proton=Neutron

Releases daughter related gamma radiation

Photons – Ionizing Radiation

• No Mass• No Charge

• Gamma- originate from within nucleus

• X-ray- originate from outside nucleus

(Bremsstrahlung)

Photons•Internal and External Exposure:Internal and External Exposure:

•Can give equally high dose to skin and Can give equally high dose to skin and

deep body core.deep body core.

•Highly PenetratingHighly Penetrating•function of photon energyfunction of photon energy•Shielding efficacy is mass dependentShielding efficacy is mass dependent

eg. Cs-137

• Temperature drop60o C - 37o C280 joules

absorbed energy

X-rays• LD/50/60

– 280 joules absorbed energy

COFFEE

Click on photo for a video on gamma rays

Linear Energy Transfer

Air Tissue

β

* * * * * * * * *

* * * * * * * * ** * * * * * *

********

* * * * * * *

Ionizing Radiation:

Any radiation capable of displacing electrons from atoms or molecules, thereby producing ions.

Examples include alpha particles, beta particles, gamma rays or x rays, and cosmic rays.

The minimum energy of ionizing radiation is a few electron volts (eV).

1010 1024 10-16

108 1022 10-14

106 1020 10-12

104 1018 10-10

102 1016 10-8

10 1014 10-6

10-2 1012 10-4

10-4 1010 10-2

10-6 108 1010-8 106 102

10-10 104 104

10-12 102 106

Energy (eV) Frequency (Hz)Wavelength (m)

12.4 eV

IR

UVVIS

Penetration

-Radioisotope produced by absorption of a neutron

-The resulting radioisotope is unstable and may emit a proton, alpha particle,beta particle, gamma ray or a combination

Mo-99* Tc-99m*

T1/2 = 66h T1/2 = 6h

MDS-Nordion

Neutron Activation

1 n0

+ U-235 U-236*

fission

heat

Fissionfragments

neutrons

Radiopharmaceuticals

Questions?• An unstable isotope has a shortage of

neutrons (too many protons), what type of particles might be emitted?– Alpha, positron

• For the same isotope, what kind of shielding would be most useful?– Alpha – anything thin– Positron – lead due to production of gamma

radiation

Questions?• An unstable isotope has a shortage of

protons (too many neutrons), what type of particles might be emitted?– Beta particle

• For the same isotope, what kind of shielding would be most useful?– Beta particle = plexiglass

So…Something to think about…• Current debates:

– Use of UV light to sterilize water?– Use of ionizing radiation to kill pathogens on

food?

• What do you think?