Radiation Safety Series 3

8/14/2019 Radiation Safety Series 3

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Radiation Safety Series

Lesson 3

Units of Measure and Dose


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Units of Measurement

R Symbol for Roentgen, a unit of measure

for X-ray and Gamma ray

rad Symbol for Radiation Absorbed Dose

Q Quality factor or relative effectiveness

rem Roentgen Equivalent Man

rem = rad x Q


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R - Roentgen

Is a unit of measure of gamma or x-ray

radiation in air.

The amount of radiation that will produce

one electrostatic unit of charge in one cubic

meter of air at standard temperature (32o F)

and standard atmospheric pressure


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rad - Radiation Absorb Dose

Roentgen is based on ionization in air andtherefore it can not be used to measure

radiation dose in animal tissue Radiant energies interact differently in

animal tissues

rad applies to various types of radiationincluding alpha, beta, gamma, x-ray andneutron


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Q Quality Factor

For each type of radiation there is a

different biological effect for the same (rad)

The Quality factor formerly known a the

relative biological effect has been

established by the National Committee on

Radiation Protection for each radiation type


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SI Units of Measure

Standard International unit equivalents

Gray (Gy) is the unit of absorbed dose

1 grey = 1 joule/kilogram = 100 rad

1 rad = 100 ergs/gram

= 0.01 joules/kilogram

= 0.01 or 10-2 gray1 R = 2.85 x 10-2 Coulombs/kilograms air


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Basic Radiation Units

milli (m) = prefix for 1/1,000 (0.001)

1 roentgen (R) = 1,000 milliroentgen (mR)

1 rem = 1,000 millirem (mrem)


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Quality Factor / Biological Effect

Alpha exposures have

a much grater

biological effect Much more damaging

X-Ray and Gamma

Ray are not as

damaging as alpha


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Quality Factor Values

Radiation Type Q

X-Ray 1

Gamma Ray 1

Beta Particles 1

Thermal Neutrons 5Fast Neutrons 10

Alpha Particles 20


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Rem Calculations

Radiation Type rad x Q = rem

X-Ray 1 1 = 1

Gamma Ray 1 1 = 1

Beta Particles 1 1 = 1

Thermal Neutrons 1 5 = 5Fast Neutrons 1 10 = 10

Alpha Particles 1 20 = 20


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ALARA

Radiation Exposure Shall Be

As Low As is Reasonably Achievable

Considering the benefits derived from its use and the

consequences incurred from any exposure


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ALARA

Time Distance and Shielding

If the job takes two do not send ten

Use Common Sense


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Determination of Occupational

Dose DDE is the dose received from x-rays and

gamma rays

CEDE is a factor only if the radiographer

had some form of internal dose from

radioactive material (airborne)

TEDE = DDE + CEDETotal Effective Deep Dose Committed Effective

Dose Equivalent Equivalent Dose Equivalent

(External) (Internal)


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TEDE Radiation Dose Limits

Annual Dose Limits

Area of exposure Occupational* PSE* PSE*

Whole body Head 5 5 25And trunk (including

male gonads) arms

above the elbow and

The knees

Lens of the Eye 15 15 75

Extremities Hands, 50 50 250elbows, feet, or legs below the knee

* Dose in rems


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Minor & Embryo/Fetus Exposure

Minors:

Age < 18 years

Dose < 10% of Dose LimitsExamples: Whole body < 0.5 rem/year

Declared Pregnant Woman:

Dose < 0.5 during entire gestation period

Embryo/Fetus:

Dose < 0.5 rem


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Planned Special Exposure Conditions

1. Must be exceptional situation (source retrieval)

2. Requires prior written authority (approved procedure)

3. Individual informed and instructed

4. Dose from previous PSEs and doses in excess of annualdose limits determined

5. Must not exceed annual dose limits and lifetime PSEs

6. Records maintained of conduct of PSEs

7. Written report to NRC or regulator

8. PSE dose recorded

9. Individual informed of dose within 30 days


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http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/bio-effects-radiation.pdf


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Works Sited

Radiation Safety Training Series Part 1: Radiation, Rudarmel

Enterprises, inc. Lake Oswego, Oregon

http://www.nrc.gov/reading-rm/doc-collections/fact-

sheets/bio-effects-radiation.pdf

Documents

Radiation Safety Series 3