RADIATION PROTECTION PRINCIPLES
Prevent the occurrence of the non-stochastic effect by restricting doses to individuals below the relevant thresholds.
Reduce induction of stochastic effectObjectives of Radiation Protection
Justification of Practice
Optimization of Protection and Safety
Recommendations (Dose Limit)Principles used in Radiation Protection Systems
Justification of Practice
No exposure is permissible unless there is benefit associated with exposure
Benefit may be to the exposed individuals or to society.
Optimization of Protection and SafetyBased 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.
Dose LimitUsed to apply controls on each individuals 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
ADL for Occupational Exposure Whole body 5 remEye 15 remPregnant Worker (9 months) 0.5 rem
ADL For Exposure of Members of PublicGeneral Public: 0.1 remMinor (18 years): 0.1 rem
ALARAALWAYS KEEP RADIATION EXPOSURES AS LOW AS REASONABLY ACHIEVABLE
Can you think of ways to do this?
TIMEThe exposure is to be kept as short as possible because the exposure is directly proportional to time.
TIMEDose = 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
DISTANCEDistance from the radiation source should be kept as great as possible
Physical Law: Inverse Square Law
DISTANCE
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 = 25 mrem/hr
Shielding Shielding takes into consideration :density and thickness of shielding materials, type of radiation
types of radiation and shielding required
Radiation protection principles are related to:
Source
Work environment
Worker
Substitution
IsolationTime Place
Shielding Removal at source
Source
Good housekeeping
Regular monitoring
Maximum allowable doseWork environment
Pre-employment examinationPeriodic medical examinationPersonal protective equipmentsLaboratory coat Overall or boiler suit Rubber gloves Overshoes Rubber boots Breathing apparatusWorker