Lecture 7-RADIATION PROTECTION

1. RADIATION
PROTECTION
Chapter 9
ORGANIZATIONS,
STANDARDS, AND
PHILOSOPHY
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2. Objectives
Identify key organizations
that recommend dose
limits
Identify organizations
that set standards
Define the philosophy of
radiation protection
Know the occupational
and public radiation
protection limits
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3. Key Scientific
Organizations
International Commission
on Radiological
Protection (ICRP)
International Atomic
Energy Agency (IAEA)
International Commission
on Radiological Units and
Measurements (ICRU)
National Council on
Radiation Protection and
Measurements (NCRP)
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4. Other
International
Organizations
United Nations:
International Labor
Organization
World Health
Organization
Food and Agriculture
Organization
Issue recommended
“safe practices”
guidelines. They do not
have authority to require
adoption of their
recommendations.
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5. Organizations that Establish
and Implement Radiation
Protection Standards
Environmental Protection
Agency
Radiation protection
guidelines
Environmental radiation
standards and regulations
Federal radiation council
Surveillance of air, food
and water
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6. Organizations That Establish
and Implement Radiation
Protection Standards
Nuclear Regulatory Commission
regulates nuclear energy industry
(commercial sector)
power reactors
fuel manufacturers
spent-fuel processing
waste management
production and use of
radioisotopes in research,
medicine, industry
issues regulations to comply with
EPA standards.
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7. Organizations that
Establish and Implement
Radiation Protection
Standards
U.S. Department of Energy
Standards for Department of
Energy Facilities
10 CFR 834, 835
Regulatory Authority Being
Challenged
Military
?
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8. Organizations that Establish
and Implement Radiation
Protection Standards
Food and Drug Administration
Center for Devices and
Radiological Health (CDRH)
responsibility for developing safety
standards for sources not
controlled by NRC (e.g., naturally
occurring or accelerator produced
radionuclides)
X-ray generators
regulations apply to manufacturers
do not have the force of law, but
may be adopted by states
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9. Organizations that Establish
and Implement Radiation
Protection Standards
The States
NRC can delegate certain health
and safety responsibilities to
states
~ 1/2 of states are “agreement”
Municipalities
large cities (e.g., New York) may
have authority to regulate
radiation sources
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10. Organizations that Establish
and Implement Radiation
Protection Standards
Department of Transportation
regulations governing
shipment of radioactive
materials.
NRC enforces
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11. The Philosophy of
Radiation Protection
Justification
Optimization
Dose limitation
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12. Categories of Exposure
Occupational Exposure
pregnant workers
all other radiation
workers
Members of the General
Public
Medical Exposure
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13. Dose Calculation
Method
How do you compare doses
delivered to different parts of
the body?
Uniform whole body irradiation
(Most likely) external source
Gamma emitter
Non uniform irradiation
(Most likely) internal source
α, β, γ, N, x-ray or other
source
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14. External
Dose
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15. Dose
Equivalent
(H)
Biological response
varies by radiations
Radiation weighting
factors used to
provide a common
scale:
H T = ∑ wR DT , R
R
DT,R is absorbed dose
T is tissue (organ)
R is radiation type R
WR is radiation
weighting factor
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16. Effective Dose
Equivalent
(HE)
Different tissues
respond
differently to
same radiation
dose
Tissue weighting
factors used to
provide a
common scale:
H E = ∑ wT H T
T
HE is the effective
dose equivalent
WT is the tissue
weighting factor
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17. Effective Dose
Equivalent, continued
Take dose equivalent for each
organ
Multiply by radiation risk
factor, WT
Sum to get “effective dose
equivalent” for the entire
body:
H E = ∑ WT H T
T
Where HT is the tissue (organ)
dose equivalent
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18. Tissue Weighting
Factors WT*
Tissue or
Organ
Tissue Weighting
Factor, WT
Gonads
0.25
Bone Marrow
(red)
0.12
Lung
0.12
Breast
0.15
Thyroid
0.03
Bone Surface
0.03
Remainder
0.30
From ICRP 20, ICRP-60 values and tissues
are different
*
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19. So… Biological Dose
Today
Measure
Exposure (X or roentgen) or
Absorbed dose (rad, Gy)
Calculate
Dose equivalent for each effected
organ (Gy*WR)
Result expressed in rem, Sv
Multiply
Each organ dose by organ-specific
radiation risk factor (Sv*WT)
Sum “risk” weighted organ doses
Result listed as “effective dose
equivalent” (rem, Sv)
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20. Occupational
Exposure Limits
To prevent nonstochastic
effects:
0.15 Sv (15 rem) lens of the eye
0.5 Sv (50 rems) all other
tissues
To limit stochastic effects:
Dose-equivalent limit from
uniform whole body irradiation is
50 mSv (5 rem) in 1 year
Effective dose-equivalent from
nonuniform irradiation 50 mSv
(5 rem) in 1 year
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21. Exposure of General
Public
For routine releases from sites:
1 mSv (100 mrem) per year
Occasional 5 mSv (500 mrem)
per year if average < 1 mSv
Remediated sites:
0.15 mSv (15 mrem) per year
e.g., Decommissioned reactors,
waste sites etc.
Air emissions:
0.1msv (10 mrem)
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22. Medical Exposure
Limits
None
Exposures must be justifiable
on the basis of benefits to the
patient
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