A Radiation Estimation Method for use in the Initial and Intermediate

Stages of a Nuclear AccidentStages of a Nuclear AccidentShi k K t R hji Ohb Mi ik Ki (Th U i it f T k )Shinsuke Kato, Ryohji Ohba, Minsik Kim (The University of Tokyo)

Jiro Yoneda(Mitsubishi Heavy Industries)

Masayuki Takigawa(Japan Agency for Marine-Earth Science and Technology)

Paul Bieringer(National Center for Atmospheric Research)

Bent Lauritzen(Denmark Technical University)

Today’s main topicsy p1. Introduction of the MEXT 2012-2014 project2. Verification and Validation study of STE method

MEXT: Ministry of Education, Science, Culture, Sports and TechnologySTE: Source Term Estimation

1

Initial and Intermediate stages of nuclear accident

Initial stage (for a few weeks) Intermediate stage (for a few years)

(a)Source Term

Radiation exposure calculation by ERMIN code

Internal exposure(b) AtmosphericDispersion

Estimation(c) Deposition (2) re-suspension in

outdoor and indoor

Gas

(5) Internal and external exposure

Dry

WetParticle

(1) Weathering effect (3) Mass balance of indoor concentration& (4) De-contamination effect

in outdoor and indoor

ERMIN: European Model for Inhabited areas code, developed by EU, after Chernobyl accident 2

References: Emergency response system of EU/ARGOS（integration system of STE and Decontamination ）（integration system of STE and Decontamination ）

3

Difficulties Developed technologiesShortage of monitoring data Application of mobile monitoringShortage of monitoring data Application of mobile monitoring

by car and airplane Unsteady wind and release Operational Source Term conditions Estimation methodSeparation of cloud and ground shines

Data filtering technique

Monitoring post: D

4000

5000

Gy/

h)

80

100

hour）

Red：gamma radiation dose

Blue： Precipitaion

shines

Time history of Gamma-ray dose rate data

0

1000

2000

3000

Rad

iation d

ose

（nG

0

20

40

60

Pre

cip

itat

ion（m

m/h

Ground-shineCloud-shine

0

3/1 3/23/33/4 3/53/6 3/73/83/93/103/113/123/133/143/153/163/173/183/193/203/213/223/233/243/253/263/273/283/293/303/31

0

Cloud shine

G d hiGround shine

Flow Chart of Source Term Estimation (STE)Observation Simulation model Uncertainty of STE

Availability and ReliabilityAssumed source intensity

Meteorological data

(Air flow)Air flow condition

•Availability and Reliability of observed data

Air Concentration

Dispersion model

•Air flow condition

•Turbulent diffusivity

STEConcentration

Soil concentration Deposition model •Deposition velocity

•Particle diameter

STE

STE

Radiation dose Radiation model

Particle diameter

•Content of radioactive STE

STE

1)Cloud-shine

2)Ground-shine

materials

•Distribution of radioactive materials

STE

3)Sky-shineradioactive materials on the ground surfaceMain object of this study

5

Operational STE methodusing the Transfer Coefficient Matrix(TCM) DataBaseusing the Transfer Coefficient Matrix(TCM) DataBase

Assumption of application1)Steady state of meteorological condition

Input typical meteorological conditions) y g

2)Short time release (< few hours)3)Nearfield monitoring points(< few kms)

conditions(Ex. 16 wind directions & 3 atmospheric stabilities = 48 cases)

Calculation of air field and dispersion under unit release rate

Example of monitoring points &TCM in Fukushima

DataBase of TCMBefore accidentDataBase of TCM

Monitoring data of gamma radiation dose STE using TCM DB

accident

g g STE using TCM DBMonitoring post: D

3000

4000

5000

ose

（nG

y/h)

60

80

100

n（m

m/hour）

Red：gamma radiation dose

Blue： Precipitaion

After accident

0

1000

2000

3/1 3/23/33/4 3/53/6 3/73/83/93/103/113/123/133/143/153/163/173/183/193/203/213/223/233/243/253/263/273/283/293/303/31

Rad

iation d

o

0

20

40

Pre

cip

itat

ion

Ground-shineCloud-shine

6

Data filtering technique of Gamma dose rate to obtain just the cloud-shine

a) Raw data)

1day

2011/3/1 3/313/11 3/15

γ-raylevel in air

se (n

Gy

/h)

b) HPF data

3/11

Normal background level γ-ray level from ground

γ-ra

yd

os

Through the HPF

3/11 3/15

γ-raylevel in air

Through the LPF

c) LPF data

3/11 3/15

Normal background level γ-ray level from ground

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Verification & Validation Study of STE based on the Wind Tunnel data (1st step)

・Observed data： W/T data (concentration)・TCM：Gaussian Plume model（fitting with W/T data） a)

b)

2.50E‐05

Concentration Distribution at a Distance of 2000m Downwind

)

1.00E‐05

1.50E‐05

2.00E‐05

C/Q(m

‐2)

TransferCoefficient

Observation

Estimation

a) Wind direction: NAccuracy of estimated Source rate：97%

5 00E 06

0.00E+00

5.00E‐06

-1700 -1200 -700 -200 300 800 1300

UC

Uncertainty factor of wind direction

‐5.00E‐06

y :Crosswind(m)

2 00E‐05

2.50E‐05

Concentration Distribution at a Distance of 2000m Downwind

b) Wind direction: N +11.25 degA f ti t d S t

1.00E‐05

1.50E‐05

2.00E 05

UC/Q(m

‐2)

TransferCoefficient

Observation

Estimation

Accuracy of estimated Source rate：3%

‐5.00E‐06

0.00E+00

5.00E‐06

-1700 -1200 -700 -200 300 800 1300

C i d( )

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Verification & Validation Study of STE based on the Wind Tunnel data (1st step)

・Observed data： W/T data modified by the meandering factor of 1 hour・TCM：Gaussian Plume model（fitting with W/T data and modified by the meandering factor of 1 hour）

a)b)

the meandering factor of 1 hour）

2 00E 05

2.50E‐05

Concentration Distribution at a Distance of 2000m Downwind

a) Wind direction: N+11.25 deg without meandering factor

Accuracy of estimated Source rate：3%

1.00E‐05

1.50E‐05

2.00E‐05

UC/Q(m

‐2)

TransferCoefficient

Observation

Estimation

Uncertainty factor of wind direction ‐5.00E‐06

0.00E+00

5.00E‐06

-1700 -1200 -700 -200 300 800 1300

y :Crosswind(m)

b) Wind direction: N +11.25 deg with d i f t f 1 h

with meandering

2.00E‐05

2.50E‐05

Concentration Distribution at a Distance of 2000m Downwind

y C oss d( )

meandering factor of 1 hourAccuracy of estimated Source rate：94%

5.00E‐06

1.00E‐05

1.50E‐05

UC/Q(m

‐2)

TransferCoefficient

Observation

Estimation

‐5.00E‐06

0.00E+00

5.00E 06

-1700 -1200 -700 -200 300 800 1300

y :Crosswind(m)

1 hour averaged data are desirable for STE9

Verification & Validation Study of STE based on the Field test data (2nd step under preparation)

Test site: MOL test reactor in

( p p p )

Belgium・Released gas: Ar41(2001.10.)・Observed data: Gamma dose

Release rateObs. data

（Q/U)Release height

Est. databy RISO g

Wind direction

RISO

10

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Long term radiation exposure modelTarget：to improve the ERMIN(European Model for Inhabited areas) code

Input data Output data

・Ground Surface condition

S il t i ti

・Long term exposure

（External and internal）・Soil contamination

・De-contamination measures

・Effect, cost and waste amount

of de-contamination

R i ff ( 1)

of de contamination

Tasks of 2012 Re-suspension coeff.(m-1)= Soil contamination (Bq/m2)/Air concentration (Bq/m3)

Tasks of 2012

・Analysis of re-suspension coefficient

・Analysis of weathering factor

・Installment of Japanese database

Weathering factor(washout effect et al.） 11

Database installed into ERMIN code

Ground surface categories in Fukushima

Soil contamination map

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Calculated results by ERMIN code

・Calculated results decrease with the passed time and the living time inside a house.More calculations are planned to check the・More calculations are planned to check the

effect of the ground surface, house and de-contamination conditions.

13

Validation of ERMIN code with Fukushima dataF k hi ERMIN

0.8

1

1.2

/h

Fukushima ERMINOBS_Ave.Ref.1Ref.1-1Ref 2 1(10%)

F0.2

0.4

0.6

0.8

μSv/ Ref.2_1(10%)

Ref.2_2(Ave.)Ref.2_3(95%)

M 0

0.2

0 365 730 1095 1460 1825 2190 2555 2920 3285 3650

time(days)

1

1.2Motomiya ERMIN

OBS_Ave.Ref.1Ref.1-1

0.4

0.6

0.8

μSv/h Ref.2_1(10%)

Ref.2_2(Ave.)Ref.2_3(95%)

0

0.2

0 365 730 1095 1460 1825 2190 2555 2920 3285 3650

time(days)

Ref.1 : Dt(t)=Di(0)・exp(-ln2/τw ・ t) ・ exp(-λi ・ t), Ref.1_1: Dt(t)=Di(0)・ exp(-λi ・ t)τw: Weathering factor (137Cs:18.4 Years, Komamura(2006)), λi: Radioactive decay factor(137Cs:0.0231), Ref.2: Golikov(1993)

14

time(days)

Summaryy

1. The operational Source Term Estimation method was developed using the database of the Transfer Coefficient Matrix based on the wind tunnel data.

2. Verification & Validation study of STE method was conducted using the wind tunnel data

3. EU-ERMIN code was applied for the estimation of long term radiation dose in Fukushima area.of long term radiation dose in Fukushima area.

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Annual schedule of each subjectsua sc edu e o eac subjec sSubjects FY2012 FY2013 FY2014

(Development of fundamental tech.)

(Validation test) (System integration)

(1)Source Term Programing Validaiton test System integration(1)Source Term Estimation(Tokyo Univ.)

g g

(2)D

Validaiton test

P i

y g

Integration testI t lli i t d t

InitialStage( Few(2)Data pre-

processing（MHI）

Programming Integration testInstalling input data ( FewWeeks)

(3)Re-suspension（Tokyo Univ ）

Data analysisImprovement of ERMIN code

Estimation of radiation dose

Long term(3)Long term exposure

LateStage( Few

（Tokyo Univ,.）International collaborations

a)Kick-off meetingsb)Invitations from

a)Visiting at RISOb)Participation into

a)Closing meetings

years)

LLNL and NCAR international conf.16