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IAEA International Atomic Energy Agency
Quantities, Exposures
and Services for
Radiation Protection
Laszlo Sagi Radiation Safety and Monitoring Section
Division of Radiation, Transport and Waste Safety
Department of Nuclear Safety and Security
IAEA
Radiation - Wavelength and energy ranges
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Sources of Ionizing Radiation
Radiation with energy sufficient to cause ionization
is called ‘ionizing radiation’
• Radionuclides
emission of alpha, beta, gamma and/or neutron radiation
• X-ray devices
emission of photons
• Accelerators
emission of photons and particle radiation
• Cosmic radiation
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• Ionizing radiation represents a health hazard
• Individual exposure needs to be restricted
• System of radiological protection shall ensure that doses received are consistently low
• Specific quantities and units are needed to − Express the risk from radiation exposure
− Establish dose limits
− Conduct protection activities
Health Effects of Ionizing Radiation
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Fluence and energy fluence, F, Ambient dose equivalent, H*(d) Equivalent dose in organ, HT Kerma, X Personal dose equivalent, Hp(d) Effective dose, E
Absorbed dose, D Directional dose equivalent, H'(d,) Committed doses, HT(t), E(t)
Exposure, X Activity, A
System of Quantities for Radiation Protection
Physical quantities Operational quantities Protection quantities
Soft-
tissue
phantom
Human
body
Source
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Operational Quantities
• Protection quantities, equivalent dose and effective dose, cannot be
measured directly
• Other measurable quantities were introduced for the purpose of
monitoring external radiation
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Personal dose equivalent, Hp(d)
Ambient dose equivalent, H* (d)
TLDs and EPDs indicate Hp(10) E
Dose rate meters measure H*(10) E
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Low dose and
low dose rate
CELL TRANSFORMATION
STOCHASTIC
EFFECTS Effective dose < 20 mSv/year
(Avaraged over five consecutive years)
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Radiation effects and limitation for planned
exposure situations by protection quantities
High dose at
high dose rate
CELL KILLING
DETERMINISTIC
EFFECTS Equivalent dose :
Extremities : < 500 mSv/year
Lens of eye :< 20 mSv/year
Sv to the lens of the eye
RADIATION
Cells’ energy absorption
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Quantities for Internal Dosimetry
• Intake
• Activity of a radionuclide taken into the body.
Unit: Bq
• Committed Effective dose
• Effective dose delivered in the course of time due to a previous intake of radioactive material.
• Time period integrated over 50 years following intake; E(50) : Sv
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Dose
20 mSv
I1
I2
I3 I4 I5
year 50 1 2
1 3
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External Radiation
• To assess the dose distribution in the body, ionizing radiation may be
classified as follows
• Weakly penetrating radiation
− Beta radiation and low-energy photons, e.g. X rays ≤ 20 keV
− Alpha particles are of no concern for external radiation
− Organs at risk: Lens of the eye, skin, shallow organs, e.g. testes
• Strongly penetrating radiation
− High-energy photons > 20 keV, e.g. gamma radiation from 137Cs or 60Co
− Neutrons of any energy
− Organs at risk: All body organs
Quantities, exposures and Services 9
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Reduce the Risk – External Radiation
Controlling the Radiation Hazard:
The three principles by which radiation dose
(and the radiation hazard) can be minimized are:
• reduce the TIME
exposed to the radiation;
• increase the DISTANCE
from the radiation source;
• use appropriate material to provide
SHIELDING from the radiation. Shielding for
manipulation of
radioactive
sources
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Shielding
Shielding
Paper Plastic Lead Paraffin
a
b+, b-
g
n
Alpha
Beta
Gamma and X-ray
Neutron
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Internal exposure
Routes of Entry, Transfer and Excretion
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Inhalation Ingestion Exhalation
Extrinsic removal
Absorption
via skin
Wound
Sweat
Urine Faeces
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Internal Dosimetry
Direct
measurements
Indirect
measurements
Body/organ
content
Dose
rate
Estimated
intake
Excretion rate
Air concentration
Committed
effective dose
e(g)j
DAC-h
m(t) m(t)
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Monitoring does not measure directly the committed effective
dose → Biogenetic models need to be applied
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Protection against ingestion
When working with radioactive materials
it is FORBIDDEN to:
• Smoke
• Eat
• Drink
• Apply cosmetics
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Protection against inhalation
• Reduce the time spent in the controlled area
• Use respiratory protection if necessary
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Internal monitoring : Whole Body Counter
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Internal monitoring : Indirect Monitoring
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Accredited Methods
• Individual monitoring
• External dosimetry by means of active personal
dosimeters, TLD (γ, β, n) and extremity (β)
• Internal Dosimetry by means of WBC for torso
and lungs (trans-U), UAL for α, β and γ emitters
• Workplace monitoring
• Dose rate, surface contamination, Pu in air and
waste, leakage test of sources
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Request for Monitoring Services
Submission of request
Request prepared by OEW Request may be cancelled at this step
Radiation Safety Technical Services Unit Review of request by approving officer
Accepted Rejected
Processing of request by
Clerk or Laboratory Assistant Provision of service
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Request for monitoring equipment
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Electronic personal dosimeters – EPDs – are available and can be provided on request
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Dose records
21 Quantities, exposures and Services
IAEA International Atomic Energy Agency
DISCUSSION
What to do when…
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What is more dangers ?
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1II
Ingestion of 60 μg of Pu-239
(4 MBq)
1 Sv
Or
Ingestion 1 kg U-238
(4 MBq)
32 mSv
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Why ?
Pu-239 U-238
Alpha energy 5.2 Mev 4.1Mev
Specific
activity*
6.6E+10 Bq/g 4.0E+03 Bq/g
Dose
conversion
(Ing.)
1.66E+04 Sv/g 3.2E-05 Sv/g
24 Topic 6 - Session 7
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Handling of radioactive material
• Can we touch by hand the radioactive
material ?
• If it emits only alpha radiation (like Pu)
Use double contention !
• If emits strongly penetrating radiation :
Use forceps or manipulator increasing the
distance
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Can we decorporate the incorporated
radioactive material ?
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RADIONUCLIDE DETECTION DECORPORATION
H-3 In vitro Plenty of liquid
Co-60 In vivo and in vitro 0.5 DTPA 250ml
Sr-90 In vitro Dilution 9 (by Sr lactate or
gluconate)
I-131 In vivo and in vitro Iodine prophylaxis (12.5-
100 mg KI, age depend.)
Cs-137 In vivo and in vitro (ferri-ferrocianid
(FeVI2)4(FeIV
2Cy12)3
U-235,238 In vitro (in vivo) Sodium bicarbonate
Pu-239 In vitro (in vivo) 0.5 g DTPA 250 ml
(diethyl triamine
pentaacetic acid)
Am-231 In vivo and in vitro 0.5 DTPA 250ml
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Thank you for your kind attention!
27 Quantities, exposures and Services
Mr Laszlo Sagi | Operational Radiation Monitoring Service Group Leader | Section of Radiation Safety and Monitoring | Division of Radiation, Transport and Waste Safety | Department of Nuclear Safety and Security | International Atomic Energy Agency | Vienna International Centre, PO Box 100, 1400 Vienna, Austria | Emai l: [email protected] | T: (+43-1) 2600-22508 | F: (+43-1) 2600 29653 | Fol low us on www.iaea.org