RADIATION PROTECTION RADIATION PROTECTION PRINCIPLESPRINCIPLES

Prevent the occurrence of the non-stochastic effect by restricting doses to individuals below the relevant thresholds.

Reduce induction of stochastic effect

Objectives of Radiation ProtectionObjectives of Radiation Protection

Justification of Practice

Optimization of Protection and Safety

Recommendations (Dose Limit)

Principles used in Radiation Principles used in Radiation Protection SystemsProtection Systems

Justification of PracticeJustification 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 Optimization of Protection and SafetySafety

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.

DoseDose LimitLimit

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

ADL for Occupational Exposure Whole body Whole body 5 rem 5 remEyeEye

15 rem 15 remPregnant Worker (Pregnant Worker (9 months9 months) 0.5 rem) 0.5 rem

ADL For Exposure of Members of PublicGeneral Public:General Public: 0.1 rem 0.1 remMinor (18 years): 0.1 remMinor (18 years): 0.1 rem

ALARA

ALWAYS KEEP RADIATION EXPOSURES AS LOW AS REASONABLY ACHIEVABLE

Can you think

of ways to do this?

TIME

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

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

DISTANCE

• Distance 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

ShieldingShielding • 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

• Isolation– Time – Place

• Shielding

• Removal at source

SourceSource

• Good housekeeping

• Regular monitoring

• Maximum allowable dose

Work environmentWork environment

• Pre-employment examination

• Periodic medical examination

• Personal protective equipments• Laboratory coat• Overall or boiler suit• Rubber gloves• Overshoes• Rubber boots• Breathing apparatus

WorkerWorker