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

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IAEA Quantities, exposures and Services 10

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

IAEA 11

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

IAEA

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: L.Sagi@iaea.org | T: (+43-1) 2600-22508 | F: (+43-1) 2600 29653 | Fol low us on www.iaea.org