Lecture 7-RADIATION PROTECTION

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Lecture 7-RADIATION PROTECTION

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Lecture 7-RADIATION PROTECTION

  1. 1. RADIATION PROTECTION Chapter 9 ORGANIZATIONS, STANDARDS, AND PHILOSOPHY Jump to first page
  2. 2. Objectives Identify key organizations that recommend dose limits Identify organizations that set standards Define the philosophy of radiation protection Know the occupational and public radiation protection limits Jump to first page
  3. 3. Key Scientific Organizations International Commission on Radiological Protection (ICRP) International Atomic Energy Agency (IAEA) International Commission on Radiological Units and Measurements (ICRU) National Council on Radiation Protection and Measurements (NCRP) Jump to first page
  4. 4. Other International Organizations United Nations: International Labor Organization World Health Organization Food and Agriculture Organization Issue recommended “safe practices” guidelines. They do not have authority to require adoption of their recommendations. Jump to first page
  5. 5. Organizations that Establish and Implement Radiation Protection Standards Environmental Protection Agency Radiation protection guidelines Environmental radiation standards and regulations Federal radiation council Surveillance of air, food and water Jump to first page
  6. 6. Organizations That Establish and Implement Radiation Protection Standards Nuclear Regulatory Commission regulates nuclear energy industry (commercial sector) power reactors fuel manufacturers spent-fuel processing waste management production and use of radioisotopes in research, medicine, industry issues regulations to comply with EPA standards. Jump to first page
  7. 7. Organizations that Establish and Implement Radiation Protection Standards U.S. Department of Energy Standards for Department of Energy Facilities 10 CFR 834, 835 Regulatory Authority Being Challenged Military ? Jump to first page
  8. 8. Organizations that Establish and Implement Radiation Protection Standards Food and Drug Administration Center for Devices and Radiological Health (CDRH) responsibility for developing safety standards for sources not controlled by NRC (e.g., naturally occurring or accelerator produced radionuclides) X-ray generators regulations apply to manufacturers do not have the force of law, but may be adopted by states Jump to first page
  9. 9. Organizations that Establish and Implement Radiation Protection Standards The States NRC can delegate certain health and safety responsibilities to states ~ 1/2 of states are “agreement” Municipalities large cities (e.g., New York) may have authority to regulate radiation sources Jump to first page
  10. 10. Organizations that Establish and Implement Radiation Protection Standards Department of Transportation regulations governing shipment of radioactive materials. NRC enforces Jump to first page
  11. 11. The Philosophy of Radiation Protection Justification Optimization Dose limitation Jump to first page
  12. 12. Categories of Exposure Occupational Exposure pregnant workers all other radiation workers Members of the General Public Medical Exposure Jump to first page
  13. 13. Dose Calculation Method How do you compare doses delivered to different parts of the body? Uniform whole body irradiation (Most likely) external source Gamma emitter Non uniform irradiation (Most likely) internal source α, β, γ, N, x-ray or other source Jump to first page
  14. 14. External Dose Jump to first page
  15. 15. Dose Equivalent (H) Biological response varies by radiations Radiation weighting factors used to provide a common scale: H T = ∑ wR DT , R R DT,R is absorbed dose T is tissue (organ) R is radiation type R WR is radiation weighting factor Jump to first page
  16. 16. Effective Dose Equivalent (HE) Different tissues respond differently to same radiation dose Tissue weighting factors used to provide a common scale: H E = ∑ wT H T T HE is the effective dose equivalent WT is the tissue weighting factor Jump to first page
  17. 17. Effective Dose Equivalent, continued Take dose equivalent for each organ Multiply by radiation risk factor, WT Sum to get “effective dose equivalent” for the entire body: H E = ∑ WT H T T Where HT is the tissue (organ) dose equivalent Jump to first page
  18. 18. Tissue Weighting Factors WT* Tissue or Organ Tissue Weighting Factor, WT Gonads 0.25 Bone Marrow (red) 0.12 Lung 0.12 Breast 0.15 Thyroid 0.03 Bone Surface 0.03 Remainder 0.30 From ICRP 20, ICRP-60 values and tissues are different * Jump to first page
  19. 19. So… Biological Dose Today Measure Exposure (X or roentgen) or Absorbed dose (rad, Gy) Calculate Dose equivalent for each effected organ (Gy*WR) Result expressed in rem, Sv Multiply Each organ dose by organ-specific radiation risk factor (Sv*WT) Sum “risk” weighted organ doses Result listed as “effective dose equivalent” (rem, Sv) Jump to first page
  20. 20. Occupational Exposure Limits To prevent nonstochastic effects: 0.15 Sv (15 rem) lens of the eye 0.5 Sv (50 rems) all other tissues To limit stochastic effects: Dose-equivalent limit from uniform whole body irradiation is 50 mSv (5 rem) in 1 year Effective dose-equivalent from nonuniform irradiation 50 mSv (5 rem) in 1 year Jump to first page
  21. 21. Exposure of General Public For routine releases from sites: 1 mSv (100 mrem) per year Occasional 5 mSv (500 mrem) per year if average < 1 mSv Remediated sites: 0.15 mSv (15 mrem) per year e.g., Decommissioned reactors, waste sites etc. Air emissions: 0.1msv (10 mrem) Jump to first page
  22. 22. Medical Exposure Limits None Exposures must be justifiable on the basis of benefits to the patient Jump to first page

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