Survey of estimation method of washout effect of radioactive - - PowerPoint PPT Presentation

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Survey of estimation method of washout effect of radioactive - - PowerPoint PPT Presentation

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Survey of estimation method of washout effect of radioactive materials from soil by rainfall Dr. Ryohji Ohba (Japan: Nuclear Safety Research Association ) Todays reports 1. Summary of J-rapid 2011 program 2. Introduction of the new MEXT

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Survey of estimation method of washout effect of radioactive materials from soil by rainfall

  • Dr. Ryohji Ohba (Japan: Nuclear Safety Research Association )

Today’s reports

  • 1. Summary of J-rapid 2011 program
  • 2. Introduction of the new MEXT 2012-2014 project
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SLIDE 2

Research Consortium items Japan UK

Project leader

  • Dr. M. Yagawa

(President, Nuclear Safety Research Association: NSRA)

  • Dr. M. Hort

(Met Office) Research members

  • Dr. R. Ohba (NSRA)
  • Prof. Y. Ishikawa (Kyoto Univ.)
  • Prof. H. Yamazawa (Nagoya

Univ.) et al. Joanne Brown (HPA) Justin Smith (HPA) Julian Hunt (House of Lord) et al. Tasks 1) Collection of Measurement data in Fukushima area 2) Analysis of radiation dose and rain radar data 3) Making of a final report 1) Joint technical meeting (1st &2nd March 2012, in HPA) 1) Information on rain deposition and washout effect from soil Supported

  • rganization

Japan Science and Technology Agency(JST) Health Protection Agency（HPA) , additionally Denmark Technical University (RISO)

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Example of the washout effect

  • n radiation dose by rainfall

Relation between radiation dose and raifall amount

0.5 1 1.5 2 2.5 3 2011/3/11 2011/4/10 2011/5/10 2011/6/9 2011/7/9 2011/8/8 2011/9/7 2011/10/7 2011/11/6 2011/12/6 2012/1/5 Date Radiation dose(microSv/hr) 50 100 150 200 Rainfall amount(mm/day) Rainfall amount Radiation dose

Observed data in Fukushima city Not significant effect Significant effect

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SLIDE 4

Time history of monitoring data

Monitoring post: D

1000 2000 3000 4000 5000 3/1 3/2 3/3 3/4 3/5 3/6 3/7 3/8 3/93/10 3/11 3/12 3/13 3/14 3/15 3/16 3/17 3/18 3/19 3/20 3/21 3/22 3/23 3/24 3/25 3/26 3/27 3/28 3/29 3/30 3/31 Radiation dose（nGy/h) 20 40 60 80 100 Precipitation（mm/hour） Red：gamma radiation dose Blue： Precipitaion

Monitoring post: D

100 200 300 400 500 9/1 9/2 9/3 9/4 9/5 9/6 9/7 9/8 9/99/10 9/11 9/12 9/13 9/14 9/15 9/16 9/17 9/18 9/19 9/20 9/21 9/22 9/23 9/24 9/25 9/26 9/27 9/28 9/29 9/30 Radiation dose（nGy/h) 20 40 60 80 100 Precipitaion（mm/hour） Red：gamma radiation dose Blue：Precipitation

a) March/2011 b) September/2011 1st release and dry deposition 3rd release and wet deposition Radioactive decay

  • f I131
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Official documents of Nuclear Safety Committee in Japan(2011,Aug.24)

  • 1. To consider mainly the effect of Cs134

and Cs137 for the decontamination

  • 2. To consider the weathering factor in

addition to the decay of radioactivity

http://www.nsc.go.jp/anzen/shidai/genan2011/genan064/index.html）

  • Ref. (1) Komamura et al., Report of Agriculture Environment Technology

Research Institute (in japanese), (2006) (2) Golikov et al., Estimation of external gamma radiation doses to the population after Chernobyl accident, The Chernobyl Papers, Vol.1 (1993)

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  • Ref. (1) Komamura et al.
  • Empirical formula from the concentration data
  • f Cs137 in wet and dry farm land of Japan
  • Total half decay period: 18.4 years

(including the radioactive decay period)

  • Weathering half decay period : 47.2 years

Farmland

  • No. of data

(Annual ave.) Formula

  • Corr. Coef.

Half decay period Wet 36 5.14Exp(- 0.044t)

  • 0.991

15.9 years Dry 36 3.89Exp(- 0.038t)

  • 0.977

18.4 years

http://www.nsc.go.jp/anzen/shidai/genan2011/genan064/index.html）

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  • Ref. (2) Golikov et al
  • Empirical formula from the radiation data of Cs

134 and Cs137 after Chernobyl accident

  • Total half decay period of Cs134: 1.8 years
  • Total half decay period of Cs134: 15.2 years

(including the radioactive decay time)

Radioactive materials Contribution ratio Total half decay period (year) 10% Value Average 95% Value Cs134 89% 1.5 1.8 2.3 Cs137 11% 10.2 15.2 19.7

http://www.nsc.go.jp/anzen/shidai/genan2011/genan064/index.html）

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Official plan of decontamination (2012.Jan. 27)

Area (present dose level) 2012 2013 2014 Dec Mar Sep Mar Preparation to live (<20mSv/y) Limitation to live(20 to 50mSv/y) Not to live (>50mSv/y)

10 to 20mSv/y 5 to 10mSv/y 1 to 5mSv/y Case study to check the method and its effect Main method of decontamination is to cut off the surface soil by appr. 5cm. Target level: less than 10mSv/y, including the weathering factor of appr. -10%/2years (12000ha) (7200ha) (9300ha)

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Difficulties of decontamination

  • Preparation of garbage area
  • Burning of tree and leaves
  • Agreement of land owner
  • Fund
  • Man-power
  • Regulatory rule of radiation
  • Pollution by ground water

And so on No available data Additional evacuation zone Emergency Protection Zone

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SLIDE 10

Relation between radiation dose and rainfall amount(1)

150mm/day 50mm/day

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Relation between radiation dose and rainfall amount(2:Fukushima city, more than 50km distance)

Relation between radiation dose and raifall amount

0.5 1 1.5 2 2.5 3 2011/3/11 2011/4/10 2011/5/10 2011/6/9 2011/7/9 2011/8/8 2011/9/7 2011/10/7 2011/11/6 2011/12/6 2012/1/5 Date Radiation dose(microSv/hr) 50 100 150 200 Rainfall amount(mm/day) Rainfall amount Radiation dose

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Ref(1): Weathering of rdiocaesium contamination on urban streets, walls and roofs (K.G. Andersson et al., J. of Environmental radioactivity, 62(2002)

  • Observed data in Denmark after Chernobyl

accident

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Ref(2):Lisbeth Warming, ”Weathering and decontamination of radioactivity deposited on concrete surfaces”,RISO-M-2473(1984)

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MEXT 2012-2014 project Advancement of Source Term Estimation model at early stage, and exposure model at intermediate stage for severe nuclear accident

Project leader: Prof. Shinsuke Kato (Tokyo University ) Co-project leader: Dr. Ryohji Ohba (Mitsubishi Heavy Industries)

  • Funded by Ministry of Education, Science, Culture,

Sports and Technology (MEXT)

  • Contracted by Japan Science and Technology

Agency (JST)

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SLIDE 15

Research Consortium

Main contrcutor：Tokyo university (1)Source Term Estimation & (3) Long term exposure model Sub-constructor: Mitsubishi Heavy Ind. (2) mobile monitoring International corporate organizations (1) US-NRC (2) US-NCAR (3) US-Laurence Livermore National Lab. (4) UK- Met office (5) Demark Institute of Technology (RISO) Stirring Comm. ・Governments ・Experts Corporate organizations ・Japan Atomic Energy Agency ・Japan Agency ｆor Marine Science & Tech. ・Nagoya university

  • Japan nuclear Power company
  • Revision program of Regulatory rule
  • Improvement of Emergency

Response system

  • Technical discussion by meetings
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・Air concentration ・Soil contamination

Analysis of re-suspension coeff.

(3)Advancement of long term exposure model

Target：to improve the ERMIN(European Model for Inhabited areas) code Input data ・Ground Surface condition ・Soil contamination ・De-conatmination measures Output data ・Long term exposure （External and internal） ・Effect, cost and garbage amount

  • f de-contamination

Tasks of 2012 ・Improve re-suspension model ・Improve Weathering model ・Installment of Japanese database

Weathering factor(washout effect et al.）

16

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SLIDE 17

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Map of ground surface categories

Tasks of 2012: Installment of Japanese GIS database for ground surface categories into ERMIN code