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Consideration of Off-site Emergency Planning Consideration of Off-site Emergency Planning and Response using Probabilistic Accident and Response using Probabilistic Accident
Consequence Assessment ModelsConsequence Assessment Models
Consideration of Off-site Emergency Planning Consideration of Off-site Emergency Planning and Response using Probabilistic Accident and Response using Probabilistic Accident
Consequence Assessment ModelsConsequence Assessment Models
M. Kimura, J. Ishikawa and T. Homma
Nuclear Safety Research Center
Japan Atomic Energy Agency (JAEA)
NREP Conference, April 22, 2009
2
IAEA Safety Requirements (GS-R-2, 2002) Safety Guide (GS-G-2.1, 2007)
– Management approach– Practical goals (8 goals)
Prevent the occurrence of deterministic health effects Prevent, to the extent practicable, the occurrence of stochastic health e
ffects
– Intervention principles– Efficient and cost-effective system
ICRP (Publ.103, 2007)– Optimization of overall strategy
Japan (NSC’s Guideline on emergency preparedness)
– No practical guidance for protective measure strategy
BackgroundBackground
3
Perform a risk informed analysis of protective measures using Level 3PSA code (OSCAAR), in order to formulate the technical basis for the effective strategy of protective measures
– Introduce a metabolic model of iodine to accurately evaluate the effect of reducing thyroid dose by administration of stable iodine
– Combination of protective measures, sheltering and evacuation with administration of stable iodine
ObjectivesObjectives
4
Accident Consequence ModelAccident Consequence Model
CHRONIC
Atmosphericdispersion
ProtectivemeasureSource
term
MS
Chronicexposure
ADD
EARLY PM
ECONO
PopulationAgricultural
data
HE
Healtheffect
HEINPUT
HINAN
CURRENT
DOSDAC
Economicloss
Earlyexposure
Meteorologicalsampling
Deposition
Meteorologicaldata
OSCAAR (Off-Site Consequence Analysis of Atmospheric Releases of radionuclides)
OSCAAR module
Preprocessor code
5
Models of OSCAARModels of OSCAAR
Atmospheric Dispersion and DepositionMulti-puff trajectory model with two scale wind fieldsTake account of temporal changes in weather conditions and variable long duration releases
Meteorological SamplingStratified sampling scheme appropriate for use with the trajectory dispersion model was
designed and developedSelect a representative sample of weather sequences for analysis
Exposure PathwaysRealistic estimates for all possible exposure pathways with protective measures with simple
models such as sheltering, evacuation, relocation and food ban – Shielding and filtering factors for sheltering– Radial evacuation
6
Metabolic Model of IodineMetabolic Model of Iodine
GUT or LUNG, Y1
THYROID, Y3
ORGANIC IODINE, Y4
BLADDEREXCRETA
INORGANIC IODINE, Y2
s2 r2
GUT or LUNG, Y1
THYROID, Y3
ORGANIC
IODINE, Y4
BLADDEREXCRETA
INORGANIC
IODINE, Y2
s2 r2
11 192 d
14 053.0 d
15 92.1 d
16 005.0 d
tMs /23
)/( 2222sr YYsr
Johnson model (1981) Reduction in the committed thyroid dose to man (for adult, 100mg)
Reduction in the committed thyroid dose to man (for adult, 100mg)
: the rate of uptake of radioactive and stable iodine by the thyroid
22 , sr
: the rate constant for uptake or excretion of iodine from each compartment
0.0
0.2
0.4
0.6
0.8
1.0
-80 -60 -40 -20 0 20 40
Time (h) before or after an intake of radioiodine
Red
uct
ion
fac
tor
(In
take
of
stab
le i
od
ine/
No
me
asu
rem
ent)
7
Source Term DevelopmentSource Term Development
・ 10-1 Iodine release fraction : Energetic events, Overpressure, ISLOCA ・ 10-5 ~ 10-4 : Containment vent ・ 10-7 ~ 10-8 : Termination
環境へのヨウ素の放出割合 発生頻度 / 全格納容器破損頻度
:Rel
ativ
e fa
ilur
e fr
eque
ncy
(eac
h /
all c
onta
inm
ent f
ailu
re s
cena
rios
)
TQUV-α
TQUX-α
TB-α
TBU-α
AE-α
TQUX-μ
TB-μ
TBU-μ
TQUX-σ
TB-σ
TBU-σ
TQUV-δ
TQUX-δ
TB-δ
TBU-δ
AE-δ
TW-θ
TC-θ
V-ν
TQUV
-υ-l
TQUX
-υ-l
TB-υ
-lTB
U-υ-
lAE
-υ-l
TQUV
-ψ-l
TBU-
ψ-l
AE-ψ
-l
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
10-10
10-9
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100BWR5/Mk-II
●: R
elea
se f
ract
ion
of I
odin
e
●□ Relative failure frequency (from INS/M03-22)
▲ JAEA evaluation
Release fraction of iodine
8
●Release time (hr) □Relative failure frequency (from INS/M03-22)
●:
Rel
ease
tim
e (h
r)
▲JAEA evaluation
Source Term Development (Cont’d)
:Rel
ativ
e fa
ilur
e fr
eque
ncy
(eac
h /
all c
onta
inm
ent f
ailu
re s
cena
rios
)
9
Strategies of protective measuresLarge early release: precautionary evacuation with stable iodine intakeLarge late release: evacuation and sheltering with stable iodine intakeControl release: sheltering with stable iodine intake
Site dataA reference site is assumed to be located at a coastal area facing the Pacific
Ocean (JAEA site at Tokai)
Source terms and PM strategy
Release scenarioRelease time
(hr after scram)Duration of release (hr)
Release fraction of iodine (%)
Large early release 3 1 7.9
Large late release 27 7 3.3
Control release 12 22 0.09
Three source term scenarios
10
全方位の 最大値
rn ri r2 r1
Calculation of dose from each pathway and time-dependent iodine concentrations in air at receptor points using OSCAAR‒ 248 weather sequences selected by a stratified sampling method
Calculation of dose reduction effects by various combinations of protective measures‒ Intervention levels for implementing each protective measure (NSC’s Guideline) Sh
eltering : 10 mSv, Evacuation : 50 mSv ( effective dose )Administration of stable iodine : 100 mSv (thyroid equivalent dose for infants)
‒ Inhalation dose due to isotope iodine based on I-131~135 contents in thyroid using Johnson model
Steps for Consequence Evaluation
Find a maximum dose at each distance and each weather sequence
Calculation of maximum dose ateach distance from the site and its probability of weather sequence‒Probability of exceeding a specific dose level‒Dose at each distance from the site at a specific
cumulative probability of weather sequences
11
For large early release, precautionary evacuation is needed before the start of release.‒ It is important to develop the preparedness action before occurring accident (e.g. EAL:
emergency action level, PAZ: precautionary action zone)Early stable iodine intake can be very effective to reduce the thyroid dose for the people within
about 20 km from the site even the delay of evacuation (consideration of distribution method).
For large early release, precautionary evacuation is needed before the start of release.‒ It is important to develop the preparedness action before occurring accident (e.g. EAL:
emergency action level, PAZ: precautionary action zone)Early stable iodine intake can be very effective to reduce the thyroid dose for the people within
about 20 km from the site even the delay of evacuation (consideration of distribution method).
Large Early Release
0.1 1 10 10010-5
10-4
10-3
10-2
10-1
100
101
102
No Shl Evac
Distance from the release point (km)
Eff
ect
ive
do
se (
Sv)
95% Met
50% Met
Sheltering
Evacuation
0.1 1 10 10010-5
10-4
10-3
10-2
10-1
100
101
102
103
104
No Evac Evac(3h) Evac(3h)+SI(0h) Evac(3h)+SI(3h)
Distance from the release point (km)T
hyr
oid
do
se (
Sv)
95% Met
50% Met
Stable iodine
Effect of the reduction for the effective dosedue to protective measures
Effect of the reduction for the thyroid dosedue to the delay of evacuation and SI intake
12
For large late release, evacuation and sheltering areas can be decided to consider weather conditions at the time of accident.
In this scenario, evacuation and sheltering area are unlikely to occur beyond 20 km and 50 km.Sheltering or evacuation with administration of stable iodine is very important to reduce the thyroid
dose.
For large late release, evacuation and sheltering areas can be decided to consider weather conditions at the time of accident.
In this scenario, evacuation and sheltering area are unlikely to occur beyond 20 km and 50 km.Sheltering or evacuation with administration of stable iodine is very important to reduce the thyroid
dose.
Large Late Release
0.1 1 10 10010-3
10-2
10-1
100
101
102
No Shl Shl+SI Evac Evac+SI
Distance from the release point (km)T
hyr
oid
do
se (
Sv)
95% Met
50% Met
Stable iodine
0.1 1 10 10010-4
10-3
10-2
10-1
100
101
No Shl Evac
Distance from the release point (km)
Eff
ect
ive
do
se (
Sv)
95% Met
50% Met
Sheltering
Evacuation
Effect of the reduction for the effective dosedue to protective measures
Effect of the reduction for the thyroid dosedue to protective measures
13
For control release, evacuation area is unlikely to occur beyond a few kilometers and sheltering area is unlikely to occur beyond about 10 km.
For very severe weather conditions, sheltering with stable iodine intake is needed.
For control release, evacuation area is unlikely to occur beyond a few kilometers and sheltering area is unlikely to occur beyond about 10 km.
For very severe weather conditions, sheltering with stable iodine intake is needed.
Control Release
0.1 1 10 10010-3
10-2
10-1
100
Met 50% Met 95%
Eff
ecti
ve d
ose
(S
v)
Distance from the release point (km)
Sheltering
Evacuation
0.1 1 10 10010-3
10-2
10-1
100
101
No Shl Shl+SI
Distance from the release point (km)T
hyr
oid
do
se (
Sv)
95% Met
50% Met
Stable iodine
Effective dose for distance from the release point
Effect of the reduction for the thyroid dosedue to sheltering and intake of stable iodine
14
For the representative source terms, the preliminary analysis has been performed using the probabilistic accident consequence model (OSCAAR) to evaluate the effectiveness of protective action strategy involving a combination of evacuation, sheltering and administration of stable iodine.
The study indicated following findings for three release scenarios.Large early release
Precautionary evacuation is needed before the start of release.Early stable iodine intake can be very effective to reduce the thyroid dose even the delay of
evacuation. It is important to develop the preparedness action before occurring accident (e.g. EAL, PAZ
, method for distribution of stable iodine).Large late release
Evacuation and sheltering areas can be decided to consider weather conditions at the time of accident.
Sheltering or evacuation with administration of stable iodine is very important to reduce the thyroid dose.
Control releaseEvacuation area is unlikely to occur beyond a few kilometers and sheltering area is unlikely
to occur beyond about 10 km. For very severe weather conditions, sheltering with stable iodine intake is needed.
Conclusions