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Radiation_exposure.pptx - DOSES AND SOURCES OF RADIATION...

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DOSES AND SOURCESOF RADIATION EXPOSURE
DOSE CONCEPTS,QUANTITIES AND UNITS
Radiation exposureFor X and gamma rays, exposure is precisely definedin terms of the amount of ionization produced in air bythe radiation sourceRadiation exposure is a measure of the intensity of the radiation field
Units of exposed doseThe SI unit:coulombs per kilogram (C/kg)Traditional (old) unit:Roentgen (R)1 R = 2.58 x 10-4coulomb/kg
Absorbed dose (D)Energy imparted to matterfrom any type of radiationD = E/mD -absorbed dose,E -energy absorbed by material of mass ‘m’
Units of absorbed doseThe SI unit:joule/kilogram or gray (Gy)1 Gy = 1 J/kgTraditional (old) unit:rad(radiation absorbed dose)1 Gy=100 rad
Variants of radiation exposureLocal irradiationTotal irradiationAcute irradiationProlonged irradiationChronic irradiationFractioned irradiationExternal irradiationInternal irradiation
Equivalent dose (HT)Accounts for biological effectper unit doseradiation weightingabsorbedfactor ( WR)dose (D)HT= WRx DX
Radiation weighting factors (WR)
Unit of equivalent doseThe SI unit:sievert (Sv)HT(Sv) = WRx D (Gy)Traditional (old) unit:rem(roentgen equivalent man)HT(rem) = WRx D (rad)1 Sv = 100 rem
Effective dose (E)Risk related parameter, taking relativeradiosensitivityof each organ and tissueinto accountE =ΣT(WTx HT)WT-tissue weighting factor for organ THT-equivalent dose received by organ or tissue TThe SI unit of effective dose:sievert (Sv)
Tissue weighting factors (WT)
Collective effective dose(S)Total radiation dose incurred bypopulationS =Σi(Eix Ni)Ei-average effective dose in the population subgroup iNi-number of individuals in subgroup iThe SI unit of collective effective dose:man-sievert (man-Sv)
Conversion between unitsused in radiation protection
Sources and levelsof radiation exposureto population
Sources of radiation exposureto people population
BackgroundradiationTerrestrial radioactivityCosmic radiationInternal radioactivity
Terrestrial radiation:external and internal exposureU-238Ra-222Th-232Ra-220
High background areas
Cosmic radiation

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Term
Fall
Professor
N/A
Tags
Ionizing radiation, ht, Sievert

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