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RADIATION PROTECTION PRINCIPLES

RADIATION PROTECTION PRINCIPLES. Objectives of Radiation Protection. Prevent the occurrence of the non-stochastic effect by restricting doses to individuals below the relevant thresholds . Reduce induction of stochastic effect. Principles used in Radiation Protection Systems.

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RADIATION PROTECTION PRINCIPLES

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  1. RADIATION PROTECTION PRINCIPLES

  2. Objectives of Radiation Protection • Prevent the occurrence of thenon-stochastic effectby restricting doses to individuals below the relevant thresholds. • Reduce induction ofstochastic effect

  3. Principles used in Radiation Protection Systems • Justification of Practice • Optimization of Protection and Safety • Recommendations (Dose Limit)

  4. Justification of Practice No exposure is permissible unless there is benefit associated with exposure Benefit may be to the exposed individuals or to society.

  5. Optimization of Protection and Safety Based on the principles of ALARA (As Low As Reasonably Achievable). For any given radiation source within a practice, the magnitude of doses, the number of people exposed should be kept to as low as reasonably achievable.

  6. DoseLimit • Used to apply controls on each individual’s accumulation of dose. • Dose limits do not include medical exposures and natural background radiation. • Annual Dose Limits (ADL) • There are different dose limits for : • radiation workers • female pregnant workers • members of the public

  7. ADL for Occupational Exposure • Whole body 5 rem • Eye 15 rem • Pregnant Worker (9 months) 0.5 rem • ADL For Exposure of Members of Public • General Public: 0.1 rem • Minor (18 years): 0.1 rem

  8. ALARA • ALWAYS KEEP RADIATION EXPOSURES AS LOW AS REASONABLY ACHIEVABLE • Can you think of ways to do this?

  9. TIME • The exposure is to be kept as short as possible because the exposure is directly proportional to time.

  10. TIME Dose = Dose rate x Time of exposure Example A researcher stands in an area where a survey meter reads 50 mrem/hr for a period of six hours. What is their total exposure as a result? 50 mrem/hr X 6 hr = 300 mrem

  11. DISTANCE DISTANCE • Distance from the radiation source should be kept as great as possible • Physical Law: • Inverse Square Law

  12. DISTANCE Doubling distance from a point source of radiation decreases dose rate to one quarter of what it was. The Inverse Square Law is: D1 X r12 = D2 X r22 Example: The dose rate one feet away from a point source is 100 mrem/hr. What is the dose rate after stepping back to a distance of two feet? D2 = (100 mrem/hr) X (1 ft)2/(2 ft)2 = 25mrem/hr

  13. Shielding • Shielding takes into consideration : • density and thickness of shielding materials, • type of radiation • types of radiation and shielding required

  14. Radiation protection principles are related to: Source Work environment Worker

  15. Source • Substitution • Isolation • Time • Place • Shielding • Removal at source

  16. Work environment • Good housekeeping • Regular monitoring • Maximum allowable dose

  17. Worker • Pre-employment examination • Periodic medical examination • Personal protective equipments • Laboratory coat • Overall or boiler suit • Rubber gloves • Overshoes • Rubber boots • Breathing apparatus

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