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