A Radiation Estimation Method for use in the Initial and Intermediate

Transcription

1 A Radiation Estimation Method for use in the Initial and Intermediate Stages of a Nuclear Accident Shinsuke Kato, Ryohji Ohba, Minsik ik Kim (The University it 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 topics 1. Introduction of the MEXT project 2. Verification and Validation study of STE method MEXT: Ministry of Education, Science, Culture, Sports and Technology STE: Source Term Estimation 1

2 Initial and Intermediate stages of nuclear accident Initial stage (for a few weeks) Intermediate stage (for a few years) (a)source Term Estimation (b) Atmospheric Dispersion (c) Deposition Radiation exposure calculation by ERMIN code (2) re-suspension in outdoor and indoor (5) Internal exposure and external exposure Gas Particle Wet Dry (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

3 References: Emergency response system of EU/ARGOS (integration system of STE and Decontamination ) 3

4 Difficulties Shortage of monitoring data Unsteady wind and release conditions Separation of cloud and ground shines Developed technologies Application of mobile monitoring by car and airplane Operational Source Term Estimation method Data filtering technique Radiation dose(ng Gy/h) Red:gamma radiation dose Blue: Precipitaion Ground-shine Monitoring post: D Cloud-shine 0 3/1 3/23/33/4 3/53/6 3/73/83/93/103/113/123/13/143/153/163/173/183/193/203/213/223/2 3/243/253/263/273/283/293/303/ hour) Precipitation(mm/h Time history of Gamma-ray dose rate data Cloud shine Ground shine

5 Flow Chart of Source Term Estimation (STE) Observation Simulation model Uncertainty of STE Meteorological data (Air flow) Assumed source intensity Availability and Reliability of observed data Air flow condition Air Concentration STE Dispersion model Turbulent diffusivity Soil concentration STE Deposition model Deposition velocity Particle diameter Radiation dose 1)Cloud-shine 2)Ground-shine 3)Sky-shine Radiation model STE Main object of this study Content of radioactive materials Distribution of radioactive materials on the ground surface 5

6 Operational STE method using the Transfer Coefficient Matrix(TCM) DataBase Assumption of application 1)Steady state of meteorological condition 2)Short time release (< few hours) 3)Nearfield monitoring points(< few kms) Example of monitoring points &TCM in Fukushima Input typical meteorological conditions (Ex. 16 wind directions & 3 atmospheric stabilities = 48 cases) Calculation of air field and dispersion under unit release rate DataBase of TCM Before accident Monitoring data of gamma radiation dose STE using TCM DB ose(ngy/h) Radiation do Red:gamma radiation dose Blue: Precipitaion Ground-shine Monitoring post: D Cloud-shine 0 0 3/1 3/23/33/4 3/53/6 3/73/83/93/103/113/123/13/143/153/163/173/183/193/203/213/223/2 3/243/253/263/273/283/293/303/ n(mm/hour) Precipitation After accident 6

7 Data filtering technique of Gamma dose rate to obtain just the cloud-shine a) Raw data γ-ray dos se (ngy/h) Through the HPF 1day γ-ray 3/ /3/1 3/15 level in air 3/31 b) HPF data Normal background level 3/11 3/15 γ-ray level from ground γ-ray level in air Through the LPF c) LPF data 3/11 3/15 Normal background level γ-ray level from ground 7

8 Verification & Validation Study of STE based on the Wind Tunnel data (1 st step) Observed data: W/T data (concentration) TCM:Gaussian Plume model (fitting with W/T data) b) a) Concentration Distribution at a Distance of 2000m Downwind 2.50E 05 UC C/Q(m 2 ) 2.00E E E 05 TransferCoefficient Observation Estimation a) Wind direction: N Accuracy of estimated Source rate: 97% 5.00E E E y :Crosswind(m) Concentration Distribution at a Distance of 2000m Downwind 2.50E E E 05 TransferCoefficient 1.50E 05 Observation Estimation 1.00E E E UC/Q(m 2 ) Uncertainty factor of wind direction b) Wind direction: N deg Accuracy of estimated Source rate: 3% E 06 C i d( )

9 Verification & Validation Study of STE based on the Wind Tunnel data (1 st 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) b) a) Concentration Distribution at a Distance of 2000m Downwind 2.50E 05 UC/Q(m 2 ) 200E E E E E 06 TransferCoefficient Observation Estimation a) Wind direction: N deg without meandering factor Accuracy of estimated Source rate: 3% 0.00E E 06 y :Crosswind(m) Coss Concentration Distribution at a Distance of 2000m Downwind 2.50E 05 Uncertainty factor of wind direction with meandering UC/Q(m 2 ) 2.00E E E 05 TransferCoefficient Observation Estimation b) Wind direction: N deg with meandering factor of 1 hour Accuracy of estimated Source rate: 94% 5.00E E E 06 y :Crosswind(m) 1 hour averaged data are desirable for STE9

10 Verification & Validation Study of STE based on the Field test data (2nd step under preparation) p Test site: MOL test reactor in Belgium Released gas: Ar41( ) Observed data: Gamma dose Obs. data Est. data by RISO Release rate (Q/U) Release height Wind direction 10 10

11 Long term radiation exposure model Target:to improve the ERMIN(European Model for Inhabited areas) code Input data Ground Surface condition Soil contamination ti De-contamination measures Output data Long term exposure (External and internal) Effect, cost and waste amount of de-contamination Tasks of 2012 Analysis of resuspension coefficient Analysis of weathering factor Installment of Japanese database Re-suspension coeff.(m-1) = Soil contamination (Bq/m2) /Air concentration (Bq/m3) Weathering factor(washout effect et al.) 11

12 Database installed into ERMIN code Ground surface categories in Fukushima Soil contamination map 12

13 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 effect of the ground surface, house and decontamination conditions. 13

14 Validation of ERMIN code with Fukushima data F μsv/ /h Fukushima ERMIN OBS_Ave. Ref.1 Ref.1-1 Ref.2_1(10%) Ref.2_2(Ave.) Ref.2_3(95%) M time(days) 0.2 μsv/h Motomiya ERMIN OBS_Ave. Ref.1 Ref.1-1 Ref.2_1(10%) Ref.2_2(Ave.) Ref.2_3(95%) time(days) Ref.1 : D t (t)=d i (0) exp(-ln2/τ w t) exp(-λ i t), Ref.1_1: D t (t)=d i (0) exp(-λ i t) τ w : Weathering factor ( 137 Cs:18.4 Years, Komamura(2006)), λ i : Radioactive decay factor ( 137 Cs:0.0231), Ref.2: Golikov(1993) 14

15 Summary 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. 15

16 Annual schedule e of each subjectss Subjects FY2012 FY2013 FY2014 (Development of fundamental tech.) (Validation test) (System integration) y g (MHI) (1)Source Term Programing g Validaiton test System integration Estimation (Tokyo Univ.) (2)Data pre- Programming Installing input data Integration test processing (3)Resuspension exposure (Tokyo Univ,.) ) (3)Long term International collaborations Data analysis a)kick-off meetings b)invitations from LLNL and NCAR Improvement of ERMIN code a)visiting at RISO b)participation into international conf. Estimation of Long term radiation dose a)closing meetings 16 Initial Stage (Few Weeks) Late Stage ( Few years)