Radiation protection Fundamentals Educational for Nuclear Engineering Classes December 2023

1. Fundamentals of
Radiation Protection
Massimo Zucchetti
A.a. 2023/2024
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2. Atomic Definitions
• Isotope Identification
– or X-A
• Activity
– Number of disintegrations (decays) per unit
time
• Half-Life
– Time for half of the material to decay away
X
A
Z
2

3. Radiation Decay
( )
( )
( )
( ) ( )
t
A
t
N
N
t
N
T
A
t
A
t
t
=

=
=
=

−

−




exp
2
ln
exp
0
2
1
0
Isotope Half-Life
222Rn 4 days
131I 8 days
3H 12.3 years
14C 5730 years
239Pu 2.4x104 years
235U 7x108 years
238U 4.5x109 years
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4. Radiation Units
• Becquerel, Bq
– One disintegration per second
– Rate at which radiation of some
type is emitted from a collection
of isotopes
• Curie, Ci
– 3.7x1010 Bq
– Amount of radiation emitted from
1 g of Ra-226
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5. Common Radioactive Decay
• Alpha, a++
– Helium
Nucleus
(4 n, 2 p)
– Captures 2 e
• Beta, b−
– Electron
• Positron, b+
• Gamma, g
– Photon
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6. Decay Chains
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7. 3 Things to Reduce Radiation
• Distance
• Shielding
• Time
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8. Distance: Inverse Square Law
Surface area of a
sphere is 4pr2
r
( ) 2
4
)
(
r
S
r
r
I
p
p
 =
=
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9. Shielding: Attenuation
I(0) I(x)
dx
S
0 exp t
I I 
−
=
 is a function of radiation energy
and shielding material
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10. Shielding Radiation
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11. Time: Duration of Exposure
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12. The absorbed dose D of radiation in any kind of
material depends on the typical ionization energy
of the particular material.
The absorbed dose is defined in terms of the
absorbed radiation energy per mass.
It therefore clearly depends on the energy loss
behavior of the various kinds of radiation.
The unit for the absorbed dose is:
1 Gray = 1Gy = 1 J/kg ( = 104 erg/kg = 100 rad )
Absorbed dose

13. Dose equivalent
• A measure of the effective
damage of radiation to matter
• For living matter (humans):
• Dose (equivalent) is measured in Sv (Sievert)
• Everybody in the US still use Rem
1 Sv = 100 Rem = 1 Gy * Q
Q (Quality Factor) depends on the type of radiation and
on its energy; it depends strongly on the ionization power of
the various kinds of radiation per path length.
Q(g, X, b) 1. Q (α) = 20 Q (n) = 2 – 10
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14. 14

15. Effects of Radiation
• Mechanistic (deterministic) Effects
– Effects such as Acute Radiation Syndrome (ARS),
skin burns, etc. for which an effective threshold of
dose must be exceeded before the effect is induced
• Stochastic effects
– Malignant and hereditary disease for which the
probability of an effect occurring rather than its
severity is regarded as a function of dose without
threshold
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16. radon
55%
cosmic
8%
Rocks and
soil
8%
from
inside the
human
body
11%
medical x-
rays
11%
nuclear
medicine
4%
consumer
products
3%
other
0%
Average Annual Radiation dose to an
individual = 360 mRem = 3.6 mSv
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17. Radiation Exposure
• External
– Type of particle
– Energy of particles
– Exposure geometry
• Internal
– Type of particle
– Energy of particle
– Critical Organ
– Pathway of removal
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18. Internal dose
• Biological half-life - time required
for body to excrete the isotope
• Effective half life- combination of
radiological half life and biological
half life
• Dose commitment: the total dose
the organ will receive from intake
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19. • Basis for classification
– Half life
– Energy and type
– Localization in the body
– Rate of elimination
– Quantities used and mode of handling
Radioisotope Hazards Classification
1Ci 10 Ci 100 Ci 10 mCi 100 mCi 1 Ci
1 mCi
Na-24, Kr-85, As-77
H-3,C-14,P-32
Ca-45,Fe-55,Bi-210
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20. Critical Organs
• If a radioactive material reaches the
bloodstream it will follow the same path as the
stable isotope of the body
– H-3, C-14, I-131, K-40
• If the nuclide taken into the body is not one
usually found in the body the radioactive
material will often behave as a chemically
similar element normally present.
– Sr-90, Ra-226 follow calcium
– Cs-137 follows potassium
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21. P-32
Ra-226
Pu-239
Rn-222
Cr-51
Co-60
Tc-99m
Au-198
Ir-192
U-235
H-3
K-40
Cs-137
Critical Organs
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I-131
Thyroid

22. Radionuclides
in the Body
• Whole Body
– 3H
– 14C
– 24Na
– 60Co
• Submersion
– 41Ar
– 87Kr
• Lung
– 222Rn
• Bone
– 90Sr
– 137Cs
– 226Ra
– 235U
– 239Pu
• Thyroid
– 131I
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23. Environmental Pathways
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24. The Regulations
(ICRP = International Council
of Radiation Protection)
Maximum dose equivalent per year:
Population: 1 mSv (100 mRem)
Workers: 20 mSv (2 Rem)
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25. Agencies
 Internationally -International Atomic Energy
Agency (IAEA)
 U.S.- Civilian nuclear safety is regulated by the
Nuclear Regulatory Commission (NRC). BUT the
safety of nuclear plants and materials controlled by the
U.S. government for research, weapons production,
and those powering naval vessels, is not governed by
the NRC.
 Europe: EURATOM
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26. International Atomic Energy Agency (IAEA)
 Est. in 1957 as the world’s “Atoms for Peace” program
 Promote peaceful use of nuclear energy and inhibit use for
military purposes
 Est. the International Nuclear Events Scale
 144 member states
 In terms of safety and security, they oversee nuclear installations,
radioactive sources, radioactive materials in transport, and
radioactive waste.
 “A core element is setting and promoting the application of
international safety standards for the management and regulation of
activities involving nuclear and radioactive materials.”-IAEA
 “The focus is on helping States prevent, detect, and respond to
terrorist or other malicious acts - such as illegal possession, use,
transfer, and trafficking - and to protect nuclear installations and
transport against sabotage.”- IAEA
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27. Nuclear-Non Proliferation Treaty
 Signers: the five Nuclear Weapons States (NWS)
recognized by the NPT: the People's Republic of China,
France, Russian Federation, the UK, and the USA.
 Notable non-signers are Israel, Pakistan, and India (the
latter two have since tested nuclear weapons, while Israel is
considered by most to be an unacknowledged nuclear
weapons state).
 North Korea was once a signatory but withdrew in January
2003. The legality of North Korea's withdrawal is debatable
but as of October 9th, 2006, North Korea clearly possesses
the capability to make a nuclear explosive device.
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28. International Nuclear Events Scale
http://www-ns.iaea.org/tech-areas/emergency/ines.htm
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29. International Nuclear Events Scale (INES)
 Level 7
A large off-site impact, widespread health and environmental effects.
Example: Chernobyl disaster (former Soviet Union) in Ukraine - 1986. – Fukushima (2011)
 Level 6
Significant off-site release, likely to require full implementation of planned countermeasures.
Example: Mayak accident (former Soviet Union) - 1957.
 Level 5
Limited off-site release, likely to require partial implementation of planned countermeasure-
example: Windscale fire (1957); or severe damage to a reactor core: Three Mile Island accident
(1979).
 Level 4
Minor off-site impact resulting in public exposure of the order of the prescribed limits, or
significant damage to a reactor core/radiological barriers or the fatal exposure of a worker.
Examples: Sellafield (UK) - 5 incidents 1955 to 1979, Saint-Laurent Nuclear Power Plant – 1980,
Buenos Aires – 1983, and Tokaimura nuclear accident (Japan) - 1999.
 Level 3
A very small off-site impact, public exposure at levels below the prescribed limits, or severe spread
of contamination on-site and/or acute health effects to one or more workers, or it is a "near accident"
event, when no safety layers are remaining.
 Level 2
This is an incident with no off-site impact, a significant spread of contamination on-site may have
occurred, or overexposure of a worker, or incidents with significant failures in safety provisions.
 Level 1
This is an anomaly beyond the authorized operating regime.
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