Transcript Overview of Protective Action for Severe Reactor

OVERVIEW OF NUCLEAR EMERGENCY
PREPAREDNESS AND RESPONSE,
IODINE PROPHYLAXIS
Module XXI
Objectives of emergency response

Mitigate accident at source

Reduce risk of serious deterministic health
effects (deaths)


Keep acute dose below health effect threshold
Reasonably reduce risk of stochastic
effects (cancer)


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Do more good than harm
Act according to international guidance
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RELEASE
Plume
RAIN
Hot Spot
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4
Fission product barriers to
prevent release
Deterministic health effects
require
- core damage
- early containment failure
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Plant staff can predict and detect
fuel cladding damage
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Symptoms
Used to
Control room
Instruments
Predict fuel damage
Water Level
Indicate imminent core damage
Core Temperature
Indicate imminent core damage
Radiation levels
Confirm core damage
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Time and size of containment failure
uncertain
FAILURE TYPE
Existing Leak
Failure to Isolate
By-pass
Explosions
Operator Initiated Venting
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TIME & SIZE
CERTAIN
No
No
No
No
Yes
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Probability of exceeding early death threshold
dose for core damage containment failure
accident
0.7
1
2
1
0.6
2
5
risk of 2 Sv
0.5
0.4
3
5
0.3
1
0.2
2
0.1
4
3
4
5
3
4
1
2
3
4
5
0
1.5
5
8
15
distance km
1 normal activity
2 basement shelter
3 large building shelter
4 Evacuation at walking speed one hour before plume
5 Evacuation starts after plume arrives
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Typical assessment core melt with early
containment failure - no rain, average
meteorological conditions
Total acute bone-marrow dose
• Early death threshold (2 Sv
bone marrow) exceeded
–at 5 km in 4 hours
–at 10 km in 24 hours
–at 20 km in 4 days
100
dose Sv
10
1
0,1
1
10
100
kilometre
4 days exposure
24 hours exposure
4 hours exposure
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After major release
from core damage accident
instruct people within 300 km
 Do
not drink milk from grazing animals
 Do
not eat potentially contaminated locally
grown vegetables (unless causes severe food shortage)
 Do
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not drink rain water
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Protective action strategy to reduce public
risk for core damage accidents

Before or shortly after release - depending on plant
conditions



evacuate or substantially shelter within 3-5 km
take thyroid blocking near the plant
After release



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promptly monito to locate areas requiring further
protective action
restrict consumption of locally grown food to 300 km
monitor to locate where food restrictions and relocation
warranted
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Psychological
considerations
Evacuations common - people do not panic
 Travel during evacuations safer than normal
travel
 Better compliance with advice if trust
maintained by:

ongoing information programme
 clear and simple advice during accident
 consistent advice and assessment (one official
point)
 using international guidance

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Psychological
effects
• Expected after nuclear accident
• At Chernobyl some actions did more harm than good
• Consider psychological effects when making
decisions
•Do not take protective action for political reasons
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Emergency workers
28 received lethal dose of radiation at Chernobyl
On- and off-site fire brigade
• did not monitor dose
• were not trained
• did not have dose limits or guidelines
Emergency workers (including off-site responders)
must
•monitor dose
•be trained
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Urgent protective action
- Should be taken before or shortly after major release
from core damage accident
- You can predict core damage before release
- You cannot predict time or size of release once core damage has
occurred
- Therefore must act on status of core
- Core damage very rare event
- Should not wait for a release before taking action
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Develop emergency
classification system

Basis for fast co-ordinated national and
regional action
Activation and notification
 Protective action before a release
 Notification of nearby countries if potential
release


Based on
Plant conditions indicating high risk of major
release (e.g. core damage)
 Environmental monitoring detecting release

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Protective action zones
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Protective actions
according to accident class
Protective Action
Class
Site Area
Emergency
yes
General
Emergency
yes
Provide responders with radiation
protection
yes
yes
Prepare the public
yes
Evacuate or shelter non-essential personnel
on-site
Evacuate or shelter PAZ
yes
Take thyroid blocking in PAZ and UAZ
yes
Monitor UAZ and take action where CILS
are exceeded
yes
Restrict fresh food and milk
yes
Notify nearby countries
yes
Record names of exposed for follow up
yes
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After start of release revise protective
action according to environmental
measurements
•BSS (IAEA, WHO, FAO, ILO, NEA/OECD, PAHO) recommend:
– generic intervention levels (GILs) –10 mSv avertable dose for sheltering, 50-100 mSv for temporary
evacuation, 100 mSv for iodine prophylaxis
– generic action levels (GALs) - e.g. at 1 kBq/kg 134,137Cs, 103,106Ru or
89Sr in food, or 0.1 kBq/kg 131I in milk, drinking water or infant food
restriction of consumption will effect
•Criteria for
–Urgent action (e.g. evacuation)
–Long term action (e.g. temporary relocation at 30 mSv/month,
permanent resettlement if lifetime projected dose is 1 Sv)
–Food restrictions
•For dose that can be prevented by action
•Intended to do more good than harm
•Taking actions at much lower levels could do more harm than good
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Technical IAEA guidance
- IAEA has developed informal guidance to use immediately to help
develop response capability
- “Generic assessment procedures for determining protective
actions during a reactor accident” (TECDOC-955)
- Accident assessment
- Emergency classification
- Protective action decision making
- Assessment of environmental data
- Monitoring
- Operational intervention levels (OILs)
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IAEA planning guidance
“Method for development of emergency response
preparedness for nuclear or radiological accident”
(TECDOC-953)
• Step-by-step process
• List of considerations
• Useful for all countries and threats (not just reactors)
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First hour schedule
for severe accident
Event detected by control room (0:00),
classified and emergency is declared (+ 5 min)
Off-site officials notified (+ 15 min)
Off-site officials decide on action (+ 30 min)
Sirens sound and public turns on radio (+45 min)
Radio message advises public to take action (+45 min)
Public starts to take action (+ 60 min)
Nearby countries notified (+60 minutes
Extensive environmental monitoring begun
Additional actions taken at levels consistent with international guidance
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Nuclear accidents


In immediate vicinity of a nuclear accident (near field),
exposure could begin immediately if released plume is at
low level.
Main route of exposure is inhalation.
Potentially larger thyroid doses from radioiodines.
Further from accident site (far field), main route of
exposure to radioiodine ingestion of contaminated food
and drink, particularly milk. Exposure by these routes
could last longer, cover larger area, and affect larger
population than exposure in near field.
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Belarus
Ukraine
1998
1997
1996
1995
1994
1993
1992
1991
1990
1989
1988
Russia
1987
100
90
80
70
60
50
40
30
20
10
0
1986
Annual num ber of cases in children
(<15 yrs old at diagnosis)
Childhood thyroid cancer around Chernobyl in
1986-1998 (children <15 years old at diagnosis)
[UNSCEAR: Exposures and Effects of the Chernobyl Accident, Annex J, New York, 2000]
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Total thyroid cancers in Belarus 1986-1998 among
children <18 years at time of accident
300
250
Number
200
150
100
50
0
0-50
50-150
150-250
250-350
350
Distance (km)
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Iodine prophylaxis –
goitre prophylaxis

Iodine prophylaxis -
[Synonyms used: stable iodine prophylaxis, thyroid blocking, iodine
administration]

Large dose of iodine that exceeds daily need about 1000
times, given once (or for a few days, max. one week) to
prevent or decrease uptake of radioactive iodine(s) into
thyroid gland and any consequent harm. Protective action
for nuclear emergency or after any accidental radioiodine
intake

Usual single dosage: 10-200 mg I/day depending on age (and
availability during emergency situation)
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Iodine prophylaxis




BSS recommends use if avertable dose to thyroid is
100 mSv
WHO recommends use for children if avertable
dose is 10 mSv, but does not recommend for adults
over 40
130 mg KI tablet daily for 1-2 days to adults
Potassium perchlorate (400 mg) for people with
iodine sensitivity
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Dose of stable iodine to
different age groups






Basic tablet contains 50 mg of iodine:
Adults: two tablets
Children and adolescents: one tablet
Infants: 1/2 tablet
Neonates: 1/4-1/2 tablet crushed in jam or drink.
Timing: ASAP. However, in continuing exposure to
radioiodine, stable I may be 50% effective even 5
hours later
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EFECTIVENESS OF THYROID BLOCKING AFFORDED|
BY 100 MG OF IODINE (130 MG OF KI)
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