Radiation Safety Series 3
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Transcript of 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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http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/bio-effects-radiation.pdf
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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