Radiation Protection-Quantities and Units-Lecture Slides, Slides of Radiation Quantities and Units

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Lecture 3 Radiation Protection Standards docsity.com Hazards Led to Safety Rules  Hazards became apparent immediately after the discovery of X-rays  Skin burns and loss of hairs of a man exposed to X- rays after diagnostic radiograph  Severe burns appeared on hands of a scientist who kept the cathode ray tube in his hands for long time  Ulcer on the skin of chest of Becquerel who kept a test tube containing Ra salt in his vest pocket  Reports of harmful radiation effects continued  Suggested radiation safety rules docsity.com Tolerance dose rate 1924  Introduction of the concept of a “tolerance” dose rate for radiation workers:  a dose rate that was considered to be one that could be tolerated indefinitely.  For purposes of application a safety factor of 10 was applied – one-hundredth of an erythema dose per month docsity.com Historical Introduction 1895  Roengten discovers x-rays –Era of bullets, bones & kidney stones. 1896  First reports of radiation damage (Thomas Edison, ..) WWI  Extensive use of x-rays on the battlefield implicated in anemia in returning soldiers. docsity.com Marie Curie’s fatal leukemia  possible result of wartime service in training military medics on use of x-ray equipment. 1921  1st Radiation Protection Committee created 1925  First Radiation Protection Standards proposed:  Limit of 1/100 of the erythema dose in 30 d (based on clinical experiences) docsity.com  ICRP has been recognized as the leading agency for providing guidance in all matters of radiation safety 1970/80’s  New radiation protection standards  based on studies of Japanese atomic bomb survivors (carcinogenic and hereditary effects) docsity.com 1991  Recommendations codified in CFR and embraced by military (e.g. 5 rem/yr for the whole body, …) . These remain as our radiation protection standards today. docsity.com Radiation Protection Agencies  Internal Agencies  US Nuclear Regulatory Programme  Pakistani Agencies docsity.com Radiation Protection Agencies cont’d Pakistani Agencies  PNRA: Pakistan Nuclear Regulatory Authority  PAEC: Pakistan Atomic Energy Commission 1. DoS: Directorate of Safety (Member fuel cycle) 2. DoS: (Member Technical) 3. DoS: (Member Power) docsity.com DEVELOPMENT OF RADIATION SAFETY 5 TA.HDARDIS: Achiov ing Inbernational Corsansus In Resgulabory Form National (lerce of Laval ler-atenal Ue ans Saori Losaraiasa a Lepiabtn aed [I # ao BEA bo pass ORCMEA Peary PAHD BEE es Pacices Merion Danie T= docsity.com ICRP Recommendations  ICRP recommendations are published in various publications  The system of dose limitation recommended by ICRP is founded on three basic tenets stated in its Publication 26 and reiterated in its Publication 60 1. Justification: No practice shall be adopted unless its introduction produces a net positive benefit. It should be pointed out that justification is societal decision, not a radiation decision. docsity.com ICRP Recemmendations Linear extrapolation ed ra Pe ee Incidence of excess cancer Cell killing “~~ possible (probable?) shape of curve op contd Fig. 9.6 Dose-response curves for acute radiation doses. Acute dose docsity.com ICRP Basic Radiation Safety Criteria  For purposes of radiations safety standards, the ICRP recognizes three categories of exposure: 1. Occupational exposure to adults who are exposed to ionizing radiation in the course of their work. Persons in this category may be called radiation workers. This category contains two subgroups a) Pregnant women b) All other radiation workers docsity.com ICRP Basic Radiation Safety Criteria cont’d 2. Members of general public 3. Medical exposures: This category deals with the intentional exposure of patients for diagnostic and therapeutic purposes by technically qualified medical and paramedical personnel. docsity.com ICRP – 26 Recommendations cont’d 2. To limit stochastic effects, the dose equivalent limit from uniform whole body irradiation was 50 mSv (5 rem) in 1 year. Medical Exposure  No specific dose limit was recommended by the ICRP for medical exposure. The commission, however, recommended that only necessary exposure should be made, that these exposures should be justified on the basis of benefits that would not otherwise have been received, and that the administrated doses should be limited to the minimum dose consistent with the medical benefit to the patient. docsity.com ICRP – 60 Recommendations Effective dose equivalent  The ICRP 60 recommendations are based on a combined concept of stochastic and non- stochastic effects. The two categories were considered together in a single index of harm called detriment, which includes consideration of both stochastic and non-stochastic effects.  The dose limits in ICRP 60 are based on a dose which, if exceeded, may lead to unacceptable consequences, be they either stochastic or non- stochastic for an individual. The dose limits are given in the following table. docsity.com ICRP – 60 Recommendations cont’d Application Occupational Public Whole body 20 mSv/year Effective dose • averaged over 5 years • maximum is 5 mSv/y 1 mSv in 1 year Annual equivalent dose to • Lens of the eye • Skin • Hands and feet 150 mSv 500 mSv 500 mSv 15 mSv 50 mSv  docsity.com ICRP – 60 Recommendations cont’d Exposure to individual in the general public cont’d  The ICRP points out that the average dose to members of the public would increase if the number of sources increase, even though the dose to no single individual exceeds the 1 mSv effective dose limit.  For this reason, the commission recommends that regional or national authorities should maintain surveillance over all the separate sources of exposure in order to control the collective total effective dose. docsity.com ICRP – 60 Recommendations cont’d Exposure of population  The ICRP made no specific recommendations for the dose limit to a population. Instead, it emphasized that each man-made contribution to the population dose must be justified by its benefits, and that limits for individual members of the population refer to the total effective dose from all sources. The dose limit to a population is thus considered to be the sum of several minimum necessary contributory doses rather than a single permissible total dose limit that is available for apportionment among several sources docsity.com Internal Exposure: ICRP–60 Criterion Annual Limit on Intake (ALI)  The annual intake (inhalation or ingestion) that would lead to an effective committed dose equivalent (a 50 year dose commitment) not exceeding 20 mSv per year.  It is that amount of activity of a radionuclide which would result in the maximum recommended dose if inhaled or ingested by “reference person”      T TT BqSvHw Sv ALI / 02.0 ,50 docsity.com Internal Exposure: ICRP–30 Criterion cont’d Annual Limit on Intake (ALI) cont’d  ALI was restricted by stochastic and non-stochastic effects      Sv/Bq H Sv 0.5 stochasticNon ALI T50,         T T50,T Sv/Bq Hw Sv 0.05 Stochastic ALI docsity.com TABLE 9.17 Annual limit on intake by workers of selected radionuclides, in microcuries.* Radionuclide Oral Inhalation 3H (tritiated water) 8.1 X 104 8.1, 10+ HOG 190 27 Sr Qf Te ice | 27 54 ICs 110 160 226Ra 1.9 0.54 235 14 0.054 239Py 5.4 0.0054 *From ICRP publication 30, 1979. ALI are rounded to two signifi- cant figures from ICRP values given in becquerels. @ docsity.com Internal Exposure: ICRP–30 Criterion cont’d Problem  Inhalation of 1 Bq of 239Pu in the form of relatively insoluble (class Y, very long pulmonary retention half-time) particle leads to the following committed dose equivalents, H50,T, from the 239Pu and its daughters in the respective target organs: lungs, 3.2  10-4 Sv; red marrow, 7.6x10-5; bone surface, 9.5x10-4; and liver, 2.1x10-4 Sv. Calculate the ALI for inhalation of this solubility class of 239Pu according to ICRP 30 criteria. [Example 8.3, p 298, Cember] docsity.com Dose conversion factor  Committed effective dose equivalent (CEDE) of a radionuclide intake can be calculated if dose conversion factor (DCF) and radio intake are known. CEDE = intake x DCF  Some of the DCFs are given in the following table docsity.com TABLE 8.9. Selected Dose Conversion Factors re contd Radionuclide/Class Intake Route Target DCESv/Bq 3H (water vapor) Inhalation Whole body (effective) 173x104 2p Ingestion Red marrow 8.09 x 10-9 oe Ingestion Whole body (effective) 237° x10? 0S r-Y/D Inhalation Bone surface F27 X1077 NS r-Y/D Inhalation Whole body (effective) 6.47 x 1078 87Cs/D Inhalation Whole body (effective) 8.63 x 10~° 37Gs Ingestion Whole body (effective) 1:35 X1078 226Ra Ingestion Bone surface 6.83 x 1076 239Pu/W Inhalation Bone surface 2.11 x 10-3 Source: From K. F, Eckerman, A. B. Wolbarst, and Allan C. B. Richardson: Limiting Values of Radionu- clide Intake and Air Concentration and Dose Conversion Factors for Inhalation, Submersion, and Inges- tion. Federal Guidance Report No. 11, EPA-520/1-88-020, 1988. @ docsity.com Dose conversion factor cont’d Problem  A worker at a heavy-water moderated nuclear reactor station accidentally inhaled 37 MBq 3H as tritiated water vapour. What is the committed effective dose equivalent (CEDE) from this exposure? [Example 8.5, p.309, Cember] docsity.com ICRP 2007 cont’d Radon  A strong correlation between residential radon exposure and risk of lung cancer as shown by the residential case-control studies (UNSCEAR- 2006)  National authorities to set national reference level for optimization of protection.  Retains the upper value of 10 mSv as individual dose reference level (ICRP-65) and corresponding activity concentration of 1500 Bq per cubic meter for workplaces and 600 Bq per cubic meter for residential dwellings docsity.com ICRP 2007 cont’d Radon cont’d  Optimized level for occupationally harmonized value = 1000 Bq per cubic meter (suggested by Commission)  Exposures to radon below the national reference level should not be regarded as part of the occupational exposure. docsity.com Excess Lung Cancer Risk  EPA estimates, based on the linear dose effect hypothesis, a one year exposure to 1 pCi/L (37 Bq/m3) of radon in equilibrium with its daughters (i.e. 0.01 WL) of lung cancer of 100 cases per million exposed individual docsity.com External and Internal Exposure cont’d Problem  During one year a radiation worker anticipates receiving a unit form external dose of 3 rem and simultaneously in haling some air borne 131I. How much of this radionuclide may the worker inhale if he is not to exceed recommended limits? Example 9.13 (Lamarsh) docsity.com ICRP 2007 Categories of exposure (Publications) 1990 recommendations and subsequent publications 2007 recommendations Planned exposure situations Individual dose limits * Public exposure (60) | mSv/vear | mSv/year Occupational exposure (60.68.75) including recovery operations (96) - lens of the eves - skin - hands and feet - intake of radionuclides - pregnant women, remainder of recegnancy 20 mSv/year average over detined periods of 5 years 150 mSy/year® 500 mSv/year > 500 mSv/year® 20 mSv/year © 2 mSvy to the surface of abdomen, | mSv to the fetus 20 mSv/year average over defined periods of 5 years 150 mSvy year? 500 mSv year? 500 mSv/vear® 20 mSv/year ° 1 mSv to the fetus docsity.com