IAEAInternational Atomic Energy Agency

Emergency Response

Protective Actions

Day 10 – Lecture 3

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Introduction

• In order to respond correctly in an emergency situation, predefined criteria for action must be available

• This lecture covers the basic

internationally accepted intervention

criteria

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Content

• Basic principles of intervention• Optimization of intervention• Projected and avertable dose• Action level dose for organs and tissue• Principles for intervention levels• Urgent protective action levels• Generic action levels for foodstuffs• Emergency worker protection guidance• Classes of emergency related work

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Practices and InterventionsSystems for Radiation Protection

• Each practice should be justified

• The doses adding up in a practice should be kept as low as reasonably achievable

• The sum of doses in a practice should be kept below specified dose limits

• Each protective action should be justified

• The level of protective actions resulting in dose subtraction should be optimized

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Basic Principles of Intervention

• All possible efforts should be made to prevent serious deterministic health effects and to reduce the occurrence of stochastic effects

• Intervention should be justified, such that the introduction of protective action should achieve more good than harm

• Levels at which intervention is introduced and at which it is later withdrawn should be optimized, so that protective action will produce the maximum net benefit

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Factors Entering Optimization

Benefit

• Avertable individual risk

• Avertable collective risk

• Reassurance

Harm• Individual physical risk• Collective physical risk• Monetary costs• Social disruption• Individual disruption• Countermeasure

anxiety• Worker risk

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Projected Dose

Time after start of the accident

Do

se

rate

Projecteddose

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Action Level of Dose for Acute Exposure to Organ or Tissue

Organ or tissue Action level of dose: Projected absorbed dose to the organ or tissue in less than 2 days (Gy)

Whole body 1

Lung 6

Skin 3

Thyroid 5

Lens of the eye 2

Gonads 3

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Avertable Dose

Time after the start of the accident

Do

se

rate

Avertabledose

t1 t2

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Principles for Intervention Levels

• Dose quantity to express the intervention level is the avertable dose

• Only pathways and doses that can be influenced by protective action should be taken into account

• Estimate of avertable doses should be as realistic as possible and for an average member of affected population

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Application

International guidance specifies:

• “Generic Intervention Levels”

(GILs), at which urgent and

long term protective actions

should be taken

• “Generic Action Levels” (GALs), at which controls should be placed on contaminated food

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GIL and GALs

• GIL and GALs set so that action would do more good than harm

• Taking action at a considerably lower level could increase overall harm to the public

• Not applicable if protective action is overly hazardous or disruptive (e,g. evacuation during a snow storm justified at a higher GIL)

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GILs for Urgent Protective ActionsTable AI-I

Protective action GIL

(dose avertable)

Sheltering 10 mSv

in 2 days

Evacuation 50 mSv

in 1 week

Iodine prophylaxis 100 mGy

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Generic Action Levels for Relocation And Resettlement Table A1-II

Protective action GIL

(Dose avertable)

Temporary relocation

30 mSv/month

Terminating temporary relocation

10 mSv/month

Permanent resettlement

1000 mSv/life time

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Generic Action Levels for FoodstuffsTable A1-III

Radio nuclides in foods destined for

general consumption

GAL

kBq/kg

Cs-134, Cs-137,

I-131, Ru-103,

Ru-106, Sr-89

1

Sr-90 0.1

Am-241, Pu-238,

Pu-239, Pu-240

0.01

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Protection of Workers Undertaking an Intervention (GS-R-2)

• No worker undertaking an intervention shall be exposed in excess of the maximum single year dose limit for occupational exposure except:

• For the purpose of saving life or preventing serious injury

• If undertaking actions intended to avert a large collective dose

• If undertaking actions to prevent the development of catastrophic conditions

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IAEA Guidance for an Emergency Worker Appendix 3

Task Total effective dose guidance

(mSv)

Life saving actions >500

Prevent the development of catastrophic conditions

>100

Emergency phase intervention >50

Longer term recovery operations and work not directly connected with an accident

Occupational exposure guidance

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Importance of Establishing Criteria (OILs)

Major lessons:

• Establish in advance, operational criteria for the instruments used

• Act on instrument readings not GILs or GALs

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GIL, GAL and Worker Guidance

• Not designed to be used during an emergency

• Must develop observable criteria to be used during an emergency• Operational intervention levels (OILs)

• Worker turn back guidance

• Measurable during an emergency with available instruments (e.g. expressed as dose rate)

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Example OILs - Dose Rates at 1 m Above Ground

Reactor release (TECDOC-955)

• Evacuate 1 mSv/h

• Restrict Food 1 Sv/h

Radiological emergency (TECDOC-1162)

• Cordon 100 Sv/h

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Expanded Guidance

• Current international guidance was found to be incomplete during past emergencies

• TECDOC - 1432 – proposes an extended framework of generic criteria that is intended to address the lessons from past emergencies

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Summary

• EP guidance is based partly on international intervention guidance • Action levels

• GILs

• GALs

• International guidance • Not useable during an emergency - need OILs

• May not address all conditions

• Taking action at lower levels could do more harm than good

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Where to Get More Information

• IAEA, Method for developing arrangements for response to a nuclear or radiological emergency, EPR-METHOD, IAEA, Vienna (2003)

• IAEA, Development of extended framework for emergency response criteria, Interim report for comments, TECDOC-1432, IAEA, Vienna (2005)