Transcript Document

Emergency Response
Protective Actions
IAEA
International Atomic Energy Agency
Day 10 – Lecture 3
Objective
To present background and guidance on
major protective actions, which may be
needed in the event of an accident to
control the radiation exposures to
members of the public
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Content
• Exposure pathways
• Protection strategy
• Protective actions
• Evacuation
• Sheltering
• Thyroid blocking
• Relocation and resettlement
• Agricultural countermeasures
• Operational Intervention Levels
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Three Major Principles
• The protective actions should
• Prevent serious deterministic effects wherever
possible
• Be justified – they should do more good than
harm
• Be optimised – they should do the most good
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Exposure Pathways and
Protective Actions
• Exposure of individuals may be external
or internal and may be incurred by
various pathways
• The various routes by which individuals
may be exposed will influence decisions
which protective actions should be
taken to prevent or reduce the exposure
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Human Exposure Pathways
Plume
Fresh produce
Cloud shine
Inhalation
Shine from ground
contamination
(ground shine)
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Immediate
ingestion
Fresh milk
Skin
contamination
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Preventive vs. Protective Actions
• Protective actions in the UPZ
• taken to avoid consequences to health
• based on measurements or predictions
• Preventive, or risk reduction actions in the PAZ
• taken to avoid the risk of exposure
• based on plant conditions
• no time for detailed analysis
• applies where protective actions may not be adequate or
fast enough
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Preventive Actions
• Should be initiated before or shortly after a
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major release from core damage accident
You can predict core damage before a
release
You can not predict the time or size of
release once you have core damage
Therefore must act on the status of the core
Should not wait for a release before taking
action
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Emergency Assessment
• Given large uncertainties and need for timely
decisions in order for protective actions to be
effective
• As simple as possible, yet effective
• Based on best understanding of severe accidents
and international guidance
• Focus on data important for decision-making
• Do not be side-tracked by data that do not
influence the decision-making
• Considerable time is needed to implement
decisions
• Only use data that will be available at the time
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Strategy to Reduce Public Risk
• Before or shortly after release - based on plant
conditions
• Evacuate or substantial shelter within 3 - 5 km
• Take thyroid blocking near the plant
• After a release
• Prompt monitoring to locate areas requiring further
protective actions.
• Restrict consumption of locally grown food to 300
km
• Monitoring to locate where food restrictions and
relocation are warranted
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Protective Actions
• Urgent protective actions
• Sheltering
• Evacuation
• Administration of stable iodine
• Longer term protective actions
• Temporary relocation
• Resettlement
• Agricultural countermeasures
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Sheltering
• Protects against external radiation from
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cloud and ground; some protection against
inhalation
Most effective when properly applied
Effectiveness depends on type of dwelling
Duration limited to about 2 days
Must be prompt
May lead to spontaneous evacuation
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Types of Shelters and Effectiveness
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Evacuation
• Most effective action for areas close to a
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facility
Must be initiated prior to a release to avoid
inhalation from the plume
Must be timely to avoid external radiation
from the ground
Difficult to manage
Spontaneous evacuation possible
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Thyroid Blocking
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KI pills
Protect against inhalation and ingestion of radioiodine only
Very effective if taken early, especially for children
Complex distribution strategies
• Difficult to distribute during emergency
• Difficult to maintain if pre-distributed
• Transient populations?
• Limited shelf life
• Large stock piles required
• Must be part of overall strategy
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Relocation and Resettlement
• To keep population out of the affected areas
• Relocation: more than 7 days but not more
than few months
• Resettlement: permanent
• Expensive
• Disruptive
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Psychological Effects of Relocation
• Relocation is especially dubious
• Has negative impact on mental well being
• If aimed to reduce risk for stochastic effects:
• Consider only future avoidable dose
• Dose already achieved cannot be reduced
• Involuntarily relocated people suffer most
• Elderly people are especially likely to suffer
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Agricultural Countermeasures
• Not to be considered urgent, though it
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should be timely
• Applied directly to plants or to soil
• Appropriate processing of food
Expensive
Great detriment to farmers:
compensation costs
Alternate food supplies required
Loss of confidence in food supplies
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Public Monitoring and Decontamination
• Skin contamination could contribute to
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deterministic effects
Public should be monitored
Should not delay evacuation
Screening or monitoring a sample is
only practical method
Instruct people to shower and change
clothes as soon as possible
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GILs and GALs
• Not directly readable on instrument
• Develop operational intervention levels (OIL)
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as part of planning
OIL readable on instruments used
OIL used during accident to make decisions
IAEA has developed suggested default OILs
Revise defaults during accident
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Gamma Dose Rate Measurements
in Environment
• Most important environmental monitoring
• Easy to measure with simple instrument and
little training
• Can use to decide where to:
• evacuate
• shelter
• give thyroid blocking
• relocate
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Default Gamma Dose Rate OILs
1.0 mSv/h ( 100 mR/h)
- Evacuate
0.2 mSv/h (20 mR/h)
- Relocate
0.1 mSv/h (10 mR/h)
- Thyroid blocking
1.0 µSv/h (100µR/h)
- Restrict local food
0.1 µSv/h (10µR/h)
- Typical Background
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Deposition Marker Isotope OILs
to Restrict Food Produced in Contaminated Area
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10 kBq/m2 - I-131 food
2 kBq/m2 - I-131 milk
2 kBq/m2 - Cs-137 food
10 kBq/m2 - Cs-137 milk
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Food Concentrations OILs
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1 Bq/kg - I-131 in food
0.1 kBq/kg - I-131 in milk, water
0.2 kBq/kg - Cs-137 in food
0.3 kBq/kg - Cs-137 in milk, water
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Summary
• Part of conventional emergency management
• Objectives of response
• Practical considerations
• Favour evacuation close in over other actions for
severe accidents
• Combination of sheltering and evacuation can be
effective
• KI pills can enhance effectiveness of sheltering
• Operational intervention level
• Establish OILs and methods before the accident, not
during !
• Use IAEA support material
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Where to Get More Information
INTERNATIONAL ATOMIC ENERGY
AGENCY
 Intervention Criteria in a Nuclear or
Radiation Emergency
Safety Series No. 109, Vienna (1994)
and
 Generic procedures for monitoring in a
nuclear or radiological emergency
IAEA-TECDOC-1092 (1999)
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