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Radioactivity:Unstable atomic nuclei will spontaneously decompose to form nuclei with a higher stability. The decomposition process is called radioactivity.

The energy and particles which are released during the decomposition process are called radiation. When unstable nuclei decompose in

nature, the process is referred to as natural radioactivity. When the unstable nuclei are prepared in the laboratory, the decomposition is

called induced radioactivity.

The curie (symbol Ci) is a non-SIunit ofradioactivity, named afterMarieandPierre Curie.[1][2]It is defined as

1 Ci = 3.7 1010decayspersecond.

1 Ci = 3.7 1010

Bq = 37 GBq

Absorbed dose:Absorbed dose (also known as total ionizing dose, TID) is a measure of the energy deposited in a medium byionizing radiationper unit

mass. It is equal to the energy deposited per unit mass of medium, which may be measured as joules per k ilogram and represented by the

equivalent SI unit,gray(Gy), or the antiquatedCGSunits,radandrep. The absorbed dose depends not only on the incident radiation but

also on the absorbing material: a soft X-ray beam may deposit four times more dose in bone than in air, or none at all in a vacuum. The

absorbed dose alone is not an adequate indicator of the likely health effects in humans. Consideration must also be given to the type of

radiation, the dose rate, the affected tissues, and other factors. For example, 1 Gy ofalpharadiation would carry a much greater risk of

cancer than 1 Gy ofphotonradiation. Further calculation can be performed to find theequivalent dosefor whole body external exposure,

theeffective dosefor partial body external exposure, or thecommitted dosefor internal exposures. These adjusted doses, measured in units

ofsievert(Sv) orrem, are much more representative of the stochastic risks to human health.

One gray is the absorption of onejouleof energy, in the form ofionizing radiation, perkilogramofmatter.

Effective doseThe Effective Dose is obtained by taking theEquivalent Dose(Dose Equivalent ) and multiplying by aTissue Weighting Factorwhich relates to theorgans / tissues under consideration. Effective Dose can therefore also be considered a doubly weightedAbsorbed Dosesince it takes into account the

type of radiation (radiation weighting factor) and the target organ / tissue. The quantity can be used to expressDetrimentto the whole body as a

summation of several different doses of radiation with varying radiation weighting factors (radiation type) and targets.

Equivalent DoseEquivalent Dose (can be refererd to asDose Equivalent ) is a quantity which takes into effect 'radiation quality', which relates to the degree to which a

type ofIonising Radiationwill produce biological damage. Equivalent Dose is obtained by multiplying theAbsorbed Doseby aRadiation Weighting

FactororQuality Factorif Dose Equivalent is used . The resulting quantity can then be expressed numerically inSieverts(Sv) or in the old units

ofRem. The quantity is independent of the absorbing material (i.e. tissue).

Radiation Energy WR (formerly Q)

x-rays,gamma rays,

beta rays,muons1

neutrons < 1 MeV 2.5 + 18.2e-[ln(E)]/6

http://en.wikipedia.org/wiki/SIhttp://en.wikipedia.org/wiki/SIhttp://en.wikipedia.org/wiki/SIhttp://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Marie_Curiehttp://en.wikipedia.org/wiki/Marie_Curiehttp://en.wikipedia.org/wiki/Marie_Curiehttp://en.wikipedia.org/wiki/Pierre_Curiehttp://en.wikipedia.org/wiki/Pierre_Curiehttp://en.wikipedia.org/wiki/Curie#cite_note-0http://en.wikipedia.org/wiki/Curie#cite_note-0http://en.wikipedia.org/wiki/Curie#cite_note-0http://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Radioactive_decayhttp://en.wikipedia.org/wiki/Secondhttp://en.wikipedia.org/wiki/Secondhttp://en.wikipedia.org/wiki/Secondhttp://en.wikipedia.org/wiki/Ionizing_radiationhttp://en.wikipedia.org/wiki/Ionizing_radiationhttp://en.wikipedia.org/wiki/Ionizing_radiationhttp://en.wikipedia.org/wiki/Gray_(unit)http://en.wikipedia.org/wiki/Gray_(unit)http://en.wikipedia.org/wiki/Gray_(unit)http://en.wikipedia.org/wiki/Centimetre_gram_second_system_of_unitshttp://en.wikipedia.org/wiki/Centimetre_gram_second_system_of_unitshttp://en.wikipedia.org/wiki/Centimetre_gram_second_system_of_unitshttp://en.wikipedia.org/wiki/Rad_(unit)http://en.wikipedia.org/wiki/Rad_(unit)http://en.wikipedia.org/wiki/Rad_(unit)http://en.wikipedia.org/wiki/Roentgen_equivalent_physicalhttp://en.wikipedia.org/wiki/Roentgen_equivalent_physicalhttp://en.wikipedia.org/wiki/Roentgen_equivalent_physicalhttp://en.wikipedia.org/wiki/Alpha_particlehttp://en.wikipedia.org/wiki/Alpha_particlehttp://en.wikipedia.org/wiki/Alpha_particlehttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Photonhttp://en.wikipedia.org/wiki/Equivalent_dosehttp://en.wikipedia.org/wiki/Equivalent_dosehttp://en.wikipedia.org/wiki/Equivalent_dosehttp://en.wikipedia.org/wiki/Effective_dose_(radiation)http://en.wikipedia.org/wiki/Effective_dose_(radiation)http://en.wikipedia.org/wiki/Effective_dose_(radiation)http://en.wikipedia.org/wiki/Committed_dosehttp://en.wikipedia.org/wiki/Committed_dosehttp://en.wikipedia.org/wiki/Committed_dosehttp://en.wikipedia.org/wiki/Sieverthttp://en.wikipedia.org/wiki/Sieverthttp://en.wikipedia.org/wiki/Sieverthttp://en.wikipedia.org/wiki/Rem_(unit)http://en.wikipedia.org/wiki/Rem_(unit)http://en.wikipedia.org/wiki/Rem_(unit)http://en.wikipedia.org/wiki/Joulehttp://en.wikipedia.org/wiki/Joulehttp://en.wikipedia.org/wiki/Joulehttp://en.wikipedia.org/wiki/Ionizing_radiationhttp://en.wikipedia.org/wiki/Ionizing_radiationhttp://en.wikipedia.org/wiki/Ionizing_radiationhttp://en.wikipedia.org/wiki/Kilogramhttp://en.wikipedia.org/wiki/Kilogramhttp://en.wikipedia.org/wiki/Kilogramhttp://en.wikipedia.org/wiki/Matterhttp://en.wikipedia.org/wiki/Matterhttp://en.wikipedia.org/wiki/Matterhttp://www.ionactive.co.uk/glossary/Equivalent_Dose.htmlhttp://www.ionactive.co.uk/glossary/Equivalent_Dose.htmlhttp://www.ionactive.co.uk/glossary/Equivalent_Dose.htmlhttp://www.ionactive.co.uk/glossary/Dose_Equivalent.htmlhttp://www.ionactive.co.uk/glossary/Dose_Equivalent.htmlhttp://www.ionactive.co.uk/glossary/Dose_Equivalent.htmlhttp://www.ionactive.co.uk/glossary/Tissue_Weighting_Factor.htmlhttp://www.ionactive.co.uk/glossary/Tissue_Weighting_Factor.htmlhttp://www.ionactive.co.uk/glossary/Tissue_Weighting_Factor.htmlhttp://www.ionactive.co.uk/glossary/Absorbed_Dose.htmlhttp://www.ionactive.co.uk/glossary/Absorbed_Dose.htmlhttp://www.ionactive.co.uk/glossary/Absorbed_Dose.htmlhttp://www.ionactive.co.uk/glossary/Detriment_Radiation.htmlhttp://www.ionactive.co.uk/glossary/Detriment_Radiation.htmlhttp://www.ionactive.co.uk/glossary/Detriment_Radiation.htmlhttp://www.ionactive.co.uk/glossary/Dose_Equivalent.htmlhttp://www.ionactive.co.uk/glossary/Dose_Equivalent.htmlhttp://www.ionactive.co.uk/glossary/Dose_Equivalent.htmlhttp://www.ionactive.co.uk/glossary/Ionising_Radiation.htmlhttp://www.ionactive.co.uk/glossary/Ionising_Radiation.htmlhttp://www.ionactive.co.uk/glossary/Ionising_Radiation.htmlhttp://www.ionactive.co.uk/glossary/Absorbed_Dose.htmlhttp://www.ionactive.co.uk/glossary/Absorbed_Dose.htmlhttp://www.ionactive.co.uk/glossary/Absorbed_Dose.htmlhttp://www.ionactive.co.uk/glossary/Radiation_Weighting_Factor.htmlhttp://www.ionactive.co.uk/glossary/Radiation_Weighting_Factor.htmlhttp://www.ionactive.co.uk/glossary/Radiation_Weighting_Factor.htmlhttp://www.ionactive.co.uk/glossary/Radiation_Weighting_Factor.htmlhttp://www.ionactive.co.uk/glossary/Quality_Factor.htmlhttp://www.ionactive.co.uk/glossary/Quality_Factor.htmlhttp://www.ionactive.co.uk/glossary/Quality_Factor.htmlhttp://www.ionactive.co.uk/glossary/Sieverts.htmlhttp://www.ionactive.co.uk/glossary/Sieverts.htmlhttp://www.ionactive.co.uk/glossary/Sieverts.htmlhttp://www.ionactive.co.uk/glossary/Rem.htmlhttp://www.ionactive.co.uk/glossary/Rem.htmlhttp://www.ionactive.co.uk/glossary/Rem.htmlhtt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1 MeV - 50 MeV 5.0 + 17.0e-[ln(2E)]/6

> 50 MeV 2.5 + 3.25e-[ln(0.04E)]/6

protons, chargedpions 2

alpha rays,

Nuclear fission products,

heavynuclei

20

where

HT is the equivalent dose absorbed by tissue T

DT,R is the absorbed dose in tissue T by radiation type R

WR is the radiation weighting factor defined by regulation

Thus for example, an absorbed dose of 1 Gy by alpha particles will lead to an equivalent dose of 20 Sv.

http://en.wikipedia.org/wiki/Protonhttp://en.wikipedia.org/wiki/Protonhttp://en.wikipedia.org/wiki/Pionhttp://en.wikipedia.org/wiki/Pionhttp://en.wikipedia.org/wiki/Pionhttp://en.wikipedia.org/wiki/Alpha_rayhttp://en.wikipedia.org/wiki/Alpha_rayhttp://en.wikipedia.org/wiki/Nuclear_fission_producthttp://en.wikipedia.org/wiki/Nuclear_fission_producthttp://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Atomic_nucleushttp://en.wikipedia.org/wiki/Nuclear_fission_producthttp://en.wikipedia.org/wiki/Alpha_rayhttp://en.wikipedia.org/wiki/Pionhttp://en.wikipedia.org/wiki/Proton