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University of Illinois at ChicagoUniversity of Illinois at ChicagoRadiation Safety SectionRadiation Safety Section
Environmental Health and Safety OfficeEnvironmental Health and Safety Office
Physics 108, 244 Physics 108, 244
Radiation Safety Physics Lecture
Ionizing RadiationIonizing Radiation
Radiation that can cause ionization of the material through which it passes either directly or indirectly
Electromagnetic radiation
Particulate radiation
Electromagnetic RadiationElectromagnetic Radiation Electro-magnetic waves (uncharged packets of energy)
propagated through space or a material medium
Wavelength, m
Frequency, s-1
Energy of one photon, eV
E ~ ν ~ 1λ_
Particulate RadiationParticulate RadiationMatter that that is propagated through space
or through a material medium
Alpha ParticlesBeta Particles (Electrons, Positrons)Neutrons (uncharged)ProtonsHeavy IonsFission Fragments
Sources of Ionizing RadiationSources of Ionizing Radiation
Radioactive Materials H-3, C-14, P-32, S-35, I-125, etc.
Radiation Producing Machines X-Ray equipment Accelerators Computer Tomography, C.T. Fluoroscopy Mammography
Radioactive DecayRadioactive Decay
Atoms that have a neutron to proton ratio that is too high or too low undergo the process of radioactive decay
Radioactive decay is the spontaneous emission of matter and/or energy from the nucleus of the atom– Particles: Alpha and/or Beta Particles– Energy: Gamma Rays and X-Rays
As a result of radioactive decay the atom transforms into a different element, which can be either stable or also radioactive
Nature of Radioactive DecayNature of Radioactive DecayDecay is random, predicting when a
given atom will decay is impossible
In sufficient numbers, the probability of decay becomes well defined
Decay Constant (λ) = The probability that any one atom will decay
ActivityActivity Activity is the rate at which nuclear transformations
occur in a radioactive material (rate of decay):
A= λN Number of radioactive atoms and, as a result,
activity decreases exponentially with time:
N = N0exp(-λt)
A = A0exp(-λt)
Half-LifeTime required for a radioactive substance to lose 50% of its activity by radioactive decay
• ½ the activity • ½ the number of radioactive atoms• ½ the radiation intensity
λT1/2 =
ln2
T1/2 T1/2 T1/2
1/2
1/4
1/8
Units of ActivityUnits of ActivityModern SI Unit
– Becquerel (Bq)– 1 Bq = 1 decay per second
Traditional Unit– Curie (Ci)– The number of radioactive decays
occurring in one gram of pure Ra-226
1 Ci = 3.7 x 1010 Bq = 37 GBq
Modes of Radioactive DecayModes of Radioactive Decay
Alpha Decay– Lowers the n/p ratio– Usually occurs when atomic number is > 83
Beta Decay (- or +)– Negative Betas (Negatrons) - Lowers the n/p ratio– Positive Betas (Positrons) - Raises the n/p ratio
Electron Capture
– Raises the n/p ratio
Gamma EmissionGamma Emission
After decay, some nuclei (called isomers) are left in an excited state (extra energy)
Excitation energy may be emitted as a gamma ray
Gamma Decay (Cs-137)Gamma Decay (Cs-137)
Cs-137
T1/2 30 yr
Ba-137m
T1/2 2.55 min
Ba-137
STABLE
661 keV GammaBeta
Absorbed DoseAbsorbed DoseABSORBED DOSE - The amount of
energy imparted per unit mass at a given location within irradiated material
RAD (rad) - The traditional unit of dose, defined as the absorption of 100 ergs per gram (0.01 J / kg or 0.01 Gy)
GRAY (Gy) – The SI unit of dose, defined as the absorption of 1 joule per kilogram (100 rads)
1 Gy = 100 rad
ExposureExposure
A measurement of the amount of ionization created by X-rays or gamma rays in a volume of air
Roentgen = 2.58 × 10-4 Coulombs / kg air
Exposure to 1 R delivers a dose of 0.96 rad to tissue
Biological EffectivenessBiological Effectiveness
Equivalent Dose – A quantity that expresses the biological effect of exposure to the different types of radiation.
Radiation weighting factor (wR) - estimate of the effectiveness per unit dose of the given radiation relative a to low-LET standard (X-ray or gamma)
Equivalent Dose = Absorbed Dose × wR
Equivalent DoseEquivalent Dose
REM (rem) - The traditional unit of dose of any radiation which produces the same biological effect as a 1 rad of absorbed dose of x- or gamma-rays
Sievert (Sv) – The SI unit of dose of any radiation that produces the same biological effect as a 1Gy of absorbed dose of x- or gamma-rays
1 Sv = 100 rem
Radiation weighting factorsRadiation weighting factors
Type of Radiation wR
X-Rays 1
Gamma-Rays 1
Beta Particles 1
Alphas 20
Neutrons 2-20
Stochastic EffectsStochastic Effects
Cancer – Radiation is a weak carcinogen
Genetic– Magnitude thought to be very small
Stochastic RisksStochastic RisksThe PROBABILITY that an effect occurs
is related to the magnitude of the radiation dose
No relation between magnitude and severity of the effect – all or none response for an individual
Same effect can be seen in unexposed individuals
Radiation Risk EstimatesRadiation Risk Estimates
International Commission on Radiological Protection (ICRP) Publication 103 (2007)
Nominal Risk for Stochastic Effects After Exposure to 1 Sv at Low Dose Rates:
Cancer 5.5% (0.055% per 1 rem)
Heritable Effects 0.2% (0.002% per 1 rem)
For acute exposures a factor of 2 is used for risk estimates
U.S. Cancer death rate: 21.20% (40.6% total)
With exposure to 5 rem: 21.48%
Radiation Levels (mrem/year)
5,000,000
TYPICAL RADIATION THERAPY:
5,000 cGy =
5,000,000 mrem
TO SINGLE ORGAN
(delivered in series of exposures)
5,000,000
TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures)
500,000
LETHAL DOSE TO 50% OF HUMANS
400,000
Radiation Levels (mrem/year)
5,000,000
TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures)
500,000
LETHAL DOSE TO 50% OF HUMANS
400,000
50,000
FIRST DETECTABLE
PHYSIO-LOGICAL EFFECTS
25,000
SMOKING 30 CIGARETTES
PER DAY
16,000
SMOKING 30 CIGARETTES PER DAY:
16,000
mrem/year
Radiation Levels (mrem/year)
50,000
FIRST DETECTABLE
PHYSIO-LOGICAL EFFECTS
25,000
SMOKING 30 CIGARETTES
PER DAY
16,000
5,000,000
TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures)
500,000
LETHAL DOSE TO 50% OF HUMANS
400,000
5,000 PART OF BODY
OCCUPATIONAL EXPOSURE
ADULTS MINORS
WHOLE BODY
SKIN
EXTREMITIES
LENS OF EYE
5,000 mrem
50,000 mrem
50,000 mrem
15,000 mrem
500 mrem
5,000 mrem
5,000 mrem
1,500 mrem
EMBRYO/FETUS
(Declared Pregnancies)
500 mrem N/A
INDIVIDUAL MEMBERS OF THE PUBLIC - 100 mrem
Radiation Levels (mrem/year)
TOTAL AVERAGE ANNUAL RADIATION DOSE TO THE US RESIDENT:
620 mrem
MAXIMUM ALLOWED
ANNUAL DOSE TO WORKER
5,000
MAXIMUM ALLOWED
ANNUAL DOSE TO WORKER
5,000,000
TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures)
500,000
LETHAL DOSE TO 50% OF HUMANS
400,000
50050,000
FIRST DETECTABLE
PHYSIO-LOGICAL EFFECTS
25,000
SMOKING 30 CIGARETTES
PER DAY
16,000
620
AVERAGE ANNUAL
RADIATION EXPOSURE
TO U.S. RESIDENT
AVERAGE NATURAL BACKGRD
311310AVIATION
200RADON
28 mrem
Radiation Levels (mrem/year)
MEDICAL
300
X-RAY DIAGNOSTICS
223
NUCLEAR MEDICINE
77
CT 147
190NUCLEAR POWER
OCCU- PATIONAL
110
Cosmic 11.00%
Terrestrial 7.00%
Radon-220 5.00%
Potassium-40 5.00%
Th & U Series 4.00%
Other <0.01%
Radon-222 68%
NCRP Report No.160, 2009
Natural Background: 311 mrem (3.11 mSv)
EPA Map of Radon Zones
J.S.Duval et al, 2005, Terrestrial radioactivity and gamma-ray exposure in the
US and Canada: U.S.G.S. Open-File Report 2005-1413
Absorbed Gamma Dose Rate in Air
CT 49%
Nuclear Medicine 26%
InterventionalFluoroscopy 14%
ConventionalRadiography andFluoroscopy 11%
Medical Exposures: 300 mrem (3.0 mSv)
NCRP Report 160, 2009
Dental bitewing
Chest Radiograph
Mammogram
Head CT
Barium Enema
Chest or abdomen CT
Coronary CT angiography Abdomen and pelvis CT
Thallium myocardial perfusion
< 10 mrem
10-20 mrem
30-60 mrem
100-200 mrem
300-600 mrem
500-700 mrem
500-1200 mrem
800-1100 mrem
3500-4000 mrem
Aviation 310Nuclear
Power 190
Industry 80
Medical 80
Education, Research 70
Government, Military 60
NCRP Report 160, 2009
Occupational: 110 mrem (1.1 mSv)
Radiation Levels (mrem/year)
5,000,000
TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures)
500,000
LETHAL DOSE TO 50% OF HUMANS
400,000
5,000
MAXIMUM ALLOWED
ANNUAL DOSE TO WORKER
500 50
29
INTERNAL R/N
TERRESTRIAL
21
COSMIC
33
50,000
FIRST DETECTABLE
PHYSIO-LOGICAL EFFECTS
25,000
SMOKING 30 CIGARETTES
PER DAY
16,000
AVERAGE NATURAL BACKGRD
311310AVIATION
200RADON
MEDICAL
300
X-RAY DIAGNOSTICS
223
NUCLEAR MEDICINE
77
CT 147
190NUCLEAR POWER
OCCU- PATIONAL
110
K-40
C-14
Rb-87Po-210
Th-230
Rn-222 U-238
Ra-228
Ra-224
Th-232
Natural Radionuclides Contained In The Body:
29 mrem (0.29 mSv)
0.6% Road Construction
35%Tobacco
27%Building Materials
26%CommercialAir Travel 6% Mining and
Agriculture
2% Fossil Fuels
<0.03% Glass & Ceramics
3% Other
NCRP Report 160, 2009
Consumer Products: 13 mrem (0.13 mSv)
Cosmic Radiation: 33 mrem (0.33 mSv)
J.S.Duval et al, 2005, Terrestrial radioactivity and gamma-ray exposure in the US and Canada: U.S.G.S. Open-File Report 2005-1413
J.S.Duval et al, 2005, Terrestrial radioactivity and gamma-ray exposure in the US and Canada: U.S.G.S. Open-File Report 2005-1413
Terrestrial Radiation: 28 mrem (0.28 mSv)Terrestrial Radiation: 28 mrem (0.28 mSv)Terrestrial Radiation: 28 mrem (0.28 mSv)Terrestrial Radiation: 28 mrem (0.28 mSv)
CONSUMER PRODUCTS
13
TERRESTRIAL
21
29
INTERNAL RN
COSMIC
33
CT 147
500
AVERAGE NATURAL BACKGRD
311310AVIATION
200RADON
MEDICAL
300
X-RAY DIAGNOSTICS
223
NUCLEAR MEDICINE
77
190NUCLEAR POWER
OCCU- PATIONAL
110
5,000,000
TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures)
500,000
LETHAL DOSE TO 50% OF HUMANS
400,000
50,000
FIRST DETECTABLE
PHYSIO-LOGICAL EFFECTS
25,000
SMOKING 30 CIGARETTES
PER DAY
16,000
5,000
MAXIMUM ALLOWED
ANNUAL DOSE TO WORKER
50 5NATURAL GAS: 2
(especially residential use)
34
AVERAGE UIC OCCUPATIONAL
EXPOSURE (751 monitored)
2
NATURAL GAS (especially residential)
SLEEPING WITH ANOTHER HUMAN
0.1
0.75
WEAPONS FALLOUT
Radiation Levels (mrem/year)
FALLOUT FROM WEAPONS TESTING: 0.75
Average UIC occupational exposure (751 monitored)
34 mrem
Exposure Rate ConstantExposure Rate Constant How to calculate your radiation dose if you know How to calculate your radiation dose if you know
the isotope, the activity & the distance.the isotope, the activity & the distance.
δΓ2R cm
mCi h
Exposure Rate CalculationExposure Rate CalculationFrom a 10From a 10μμCi Cs-137 Point Source at 1 cmCi Cs-137 Point Source at 1 cm
(3.287 is the Exposure Rate Constant for Cs-137)(3.287 is the Exposure Rate Constant for Cs-137)
=
2
-22 1
dcm
R cm 1000mRX × mCi× ×m
ACi h R
=
2
3.287Rh
0.011000mRX × × ×1
1 R
= 32.87mRXh
X•
X•
•X
Exposure Rate at Various Exposure Rate at Various Distances From 10Distances From 10μci of Cs-137μci of Cs-137
0.1 cm 3287 mR/h1.0 cm 32.87 mR/h10 cm 0.3287 mR/h100 cm 0.003287 mR/h
CONSUMER PRODUCTS
13
TERRESTRIAL
21
29
INTERNAL RN
COSMIC
33
CT 147
500
AVERAGE NATURAL BACKGRD
311310AVIATION
200RADON
MEDICAL
300
X-RAY DIAGNOSTICS
223
NUCLEAR MEDICINE
77
190NUCLEAR POWER
OCCU- PATIONAL
110
5,000,000
TYPICAL THERAPY X-RAY TO SINGLE ORGAN (series of exposures)
500,000
LETHAL DOSE TO 50% OF HUMANS
400,000
50,000
FIRST DETECTABLE
PHYSIO-LOGICAL EFFECTS
25,000
SMOKING 30 CIGARETTES
PER DAY
16,000
5,000
MAXIMUM ALLOWED
ANNUAL DOSE TO WORKER
50 5
34
AVERAGE UIC OCCUPATIONAL
EXPOSURE (751 monitored)
2
NATURAL GAS (especially residential)
SLEEPING WITH ANOTHER HUMAN
0.1
0.75
WEAPONS FALLOUT
Radiation Levels (mrem/year)
CONSUMER PRODUCTS: 0.03
(without building materials and tobacco)
10 hours of Physics Lab using
10 µCi Cs-137 source: 0.03
Standard Warning SignStandard Warning SignFor Radioactive Material Use AreasFor Radioactive Material Use Areas
Used to indicate an area is authorized for radioactive material use – BUT only by projects that have it listed in their authorization!
Basic Principles of Basic Principles of Radiation ProtectionRadiation Protection
Time
Distance
Shielding
Contamination Control
DistanceDistance Inverse Square
Law
Radiation intensity is inversely proportional to the distance squared d1 d2
I1 I2
I1
I2d2
2
d12
=
Rules for Handling SourcesRules for Handling SourcesDO NOT place your
finger or any other part of your body directly over the face of the source
Handle the sources only by their edges
Minimize the time sources are handled
Increase distance to minimize exposureSign sources in and out with the T.A.
Lab CoatsLab Coats
You will be working with Sealed Sources only.
Lab coats and gloves are to be worn in the lab when handling UNSEALED radioactive material.
When working with SEALED radioactive sources, lab coats and gloves are NOT required.