(2017/11/27@Kiev)

Ｉ Ｎ Ｓ Ｉ Ｇ Ｈ Ｔ Ｓ 　 Ｏ Ｂ Ｔ Ａ Ｉ Ｎ Ｅ Ｄ 　 Ｆ Ｒ ＯＭ　 Ｅ Ｎ Ｖ Ｉ Ｒ Ｏ Ｎ ＭＥ Ｎ Ｔ Ａ Ｌ 　

Ｄ Ｙ Ｎ Ａ ＭＩ Ｃ Ｓ 　 Ｓ Ｔ Ｕ Ｄ Ｙ 　 Ｆ Ｏ Ｒ 　 Ｆ ＵＫ Ｕ Ｓ Ｈ Ｉ ＭＡ 　

Ｒ Ｅ ＭＥ Ｄ Ｉ Ａ Ｔ Ｉ Ｏ ＮFukushima Environmental Safety Center

Sector of Fukushima Research and DevelopmentJapan Atomic Energy Agency

Akihiro Kitamura

Outline of the talk

• Purpose of research

• Researches on transport behavior of radionuclides• Forest, river system, estuary

• Predictive modeling• Mechanistic approaches• Radiocesium behavior in the Ukedo river system• Comprehensive Evaluation System

2

Contaminated Area- Chernobyl and Fukushima -

3Ministry of Economy, Trade and Industry (2013)

kBq/m2

Contaminated area (km2)

Chernobyl Fukushima ratio

1,480 - 3,100 200 6%

555 - 1,480 7,200 400 6%

185 - 555 18,900 1,400 7%

37 - 185 116,900 6,900 6%

Total 146,100 8,900 6%

Surface contamination density [kBq/m2]

3,700 –1,480 – 3,700 555 – 1,480 185 – 555 37 – 185

4　 Initial Cs distribution: Forests occupied the most

WastelandPaddy fieldBeachOceanRiver and LakeForestBuilt-up arearoad / railwaysGolf fieldCrop fieldOther land use

Land use distribution in eastern Fukushima

Land use

Area (km2)

Initial Cs (TBq)

Forest 5,330 920

Total 8,370 1,300

Forest% 64% 69%

Kitamura et al, Anthropocene (2014)

Redistribution and evolution of concentration of radioactive CsRedistribution and evolution of concentration of radioactive Cs

Consequence of redistribution and evolutionConsequence of redistribution and evolution

Background of the project 5

dissolutiondissolutiondissolved

Cs

particulateCs

desorptiondesorption

transfer to agricultural / aquatic products and drinking water

sedimentation near living sphere

transport to the ocean

erosionerosion

run-off / river transportrun-off / river transport

sedimentationsedimentation

Internal exposure

External exposure

wash offwash off

transfer to forest products

accumulation in forests near living sphere

Redistribution and evolution of concentration of radioactive CsRedistribution and evolution of concentration of radioactive Cs

Consequence of redistribution and evolutionConsequence of redistribution and evolution

Objectives of the F-TRACE project 6

Developing calculation tools for;• predictive modeling of transport,• evaluation of transfer, and • evaluation of external / internal

dose, and database.

Establishing the system supplying information to the government, regional municipalities and habitants; • on future dose, future concentration of products, etc., • by showing analytical results visually and clearly,• with scientific understandings obtained in various investigations.

Obtaining data on Cs behaviors in the environment of each river system.

Understanding the processes of generation of dissolved Cs, transport of particulate Cs.

Kitamura et al, Nucl Sci Eng (2015)

Research area

1F NPP

Odaka

Ukedo/TakaseMaeda

Kuma/Ogawara

Tomioka/Oginosawa

Kido

Ohta

7

Ide

・ Systematic research on each river system from forests to estuary makes it possible to evaluate the behavior in whole catchment.

・ Comparing behaviors in several river systems with different characteristics is useful to clarify factors dominate transport of Cs.

Kawamata(Forest only)

Outline

• Purpose of research

• Researches on transport behavior of radionuclides• Forest, river system, estuary

• Predictive modeling• Mechanistic approaches• Radiocesium behavior in the Ukedo river system• Comprehensive Evaluation System

8

Observation issues and points (examples of Namie town) 9

　 Forest Deposition behavior using lichens　 River ( 　　 continuous monitoring system) Dose rate and weather condition　 Dam reservoir Mountain　 Estuary

10

Stem

flow

Thro

ughf

all

Mineral soil

　　 Organic layerBasement

Infil

trat

ion

Rain fall

Surface runoff　 Soil loss

Litt

er fa

ll

　 Forest: Cs transport processes in forests

11

Stem

flow

Thro

ughf

all

Mineral soil

　　 Organic layerBasement

Infil

trat

ion

Rain fall

Surface runoff　 Soil loss

Litt

er fa

ll

　 Forest: water, litter and soil movement

Washoff rates were quite low in all observation areas.

Niizato et al, J Environ Radioact (2016)

2013(duration)

2014(duration)

Kawauchi (KA)Evergreen

(Japanese cedar) Steep slope

0.10%(6.10-11.18)

0.06%(4.11-10.8)

Kawamata (KE)Deciduous

Gentle slope

0.02%(3.29-11.19)

0.10%(4.7-10.20)

Kawamata (KW)Deciduous

Steep slope

0.05%(6.28-11.19)

0.11%(4.7-10.20)

Cs-137 washoff rate accompanied by the transportation of particulate matter.

12

Stem

flow

Thro

ughf

all

Mineral soil

　　 Organic layerBasement

Infil

trat

ion

Rain fall

Surface runoff　 Soil loss

Litt

er fa

ll

　 Forest: water, litter and soil movement

Evolution of depth profiles of Cs in the topsoil of forest floor (KA).

Infiltration of Cs was quite slow.

Cs deposition (kBq/m2/cm)

Dep

th (

cm)

•Ridge•Slope: 8°•Sampling　 Jan. 2013

Oct. 2014

•Bottom of valley•Slope: 20°•Sampling

　 Jan. 2013Oct. 2014

Dep

th (

cm)

Cs deposition (kBq/m2/cm)

Dissolved Cs in a mountain stream

Stream waterGroundwaterPore water collected by suctionPore water naturally oozing out

a. well for groundwater b. natural lysimeter c. suction lysimeter

Well for GW

Depth of suction lysimeter

Water table

observation of flow rate

observation of flow rate

Flowing out point of stream

13

Observation equipments set up in the evergreen forest in Kawamata.

Dissolved Cs in a mountain stream

Water table

Depth of suction lysimeter

July 2015

Sept. 2015

14

• Concentration of dissolved Cs drastically increased near the flowing out point. => Concentration of Cs was controlled by dissolution from litter or desorption

from soil near the flowing out point.

Stream waterGroundwaterPore water collected by suctionPore water naturally oozing out

Numbers indicate dissolved Cs-137 concentration in mBq/L;

Onda, results of commissioned study by JAEA

Ukedo river system

Ukedo river- Dam at middle- Upper: Highly contaminated

Takase river- No dam- Upper: Less contaminated

15

Ogaki dam lake

FDNPS

Dissolved Cs in the Ogaki dam lake 16

2014.3.22014.9.182015.4.62015.10.230,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7 流入水（請戸川）流入水（小出谷川）放流水

Diss

olve

d 13

7Cs [

Bq/L

]

Evolution of concentration of dissolved Cs in inflow and outflow waters of Ogaki dam lake (Ukedo river).

Inflow 1

Inflow 2

Outflow

< 1 Bq/L in 2014. Seasonal change ← Biodegradation? Less decreased ← Any buffering processes? Outflow concentration was defined by inflows.

Inflow 1Inflow 2

Outflow

Funaki et al, J Environ Radioact (submitted)

Cs discharged to the ocean in FY 2015 17

River

Estimated amount of discharge

Annual discharge Discharge at the high water event on Sept.

Amount(TBq)

Ratio to initial

deposition

Amount(TBq)

Ratio to annual

discharge

Odaka 0.074 　 0.5 % 0.053 72 %

Ukedo > 0.224 　

> 0.1 % 0.089 48 %

Takase 1.185 0.4 % 0.811 79 %

Maeda 0.057 　 0.1 % 0.035 73 %

Kuma 0.312 0.5 % 0.233 79 %

Tomioka 0.022 　 0.1 % 0.013 58 %

with dam

with dam

Discharge rates of Cs to the ocean were extremely low, especially in rivers with dams.

Outline

• Purpose of research

• Researches on transport behavior of radionuclides• Forest, river system, estuary

• Predictive modeling• Mechanistic approaches• Radiocesium behavior in the Ukedo river system• Comprehensive Evaluation System

18

Mechanistic approaches for future predictions 19

Suspended solid

Dissolved RCs

SS-bound RCs

advection dispersion inflow/outflow sedimentation/resuspension

advection dispersion decay inflow/outflow sorption/desorption to SS and river bed

advection dispersion decay inflow/outflow sorption/desorption sedimentation /resuspension

20　Prediction of Cs migration in dam reservoir

20

TODAM: 1D transport model for contaminant in rivers

Inflow 1

Inflow 2

Concentration of137Cs in the inflows (input of calculation) and outflow (output) of Ogaki dam lake in the typhoon in 2013.

outflow

Calculated values of outflow agreed well to those of observed . Around 90% of Cs in inflows could be accumulated in the lake.

Conc

entr

atio

n of

Cs-

137

(Bq/

L)

Inflow 1 (obs.)Inflow 2 (obs.)Outflow (obs.)Inflow 1 (input)Inflow 2 (input)Outflow (output)

Inflow 1

Inflow 2

outflow

Kurikami et al, J Enviorn Radioact (2014)

21 3D grid-block system for watershed modeling

・　 Horizontal resolution of the grid-blocks was between 30-250 m (average 100 m).・　 Subsurface geology in the vertical direction consisted of 28 layers・　 Plus one air layer and one surface layer. ・　 Thickness of the vertical layers varied. ・　 Total number of grid-blocks created was 4,224,000.

Kitamura et al, ESPL (2016)

Prediction of Cs discharge from the river

It can be applied to predict the behavior of Cs depending on precipitation.

Wa

ter

flow

[m

3 ]

137C

s d

isch

arg

e [

GB

q]

Water flow, soil loss and Cs-137 discharge for 3 days during each high water event.

Relationship to precipitation

0,0E+0

1,0E+7

2,0E+7

3,0E+7

4,0E+7

5,0E+7

6,0E+7

0,0E+0

2,0E+6

4,0E+6

6,0E+6

8,0E+6

1,0E+7

0,0E+0

1,0E+2

2,0E+2

3,0E+2

4,0E+2

5,0E+2

6,0E+2

0 50 100 150 200 250 3000,0E+0

2,0E+6

4,0E+6

6,0E+6

8,0E+6

1,0E+7

0 50 100 150 200 250 3000,0E+0

1,0E+2

2,0E+2

3,0E+2

4,0E+2

5,0E+2

6,0E+2

0 50 100 150 200 250 3000,0E+0

1,0E+7

2,0E+7

3,0E+7

4,0E+7

5,0E+7

6,0E+7

Precipitation per event [mm]

22

3 d

ays

so

il lo

ss [

kg]

3 d

ays

wa

ter

flow

[m

3]

3 d

ays

dis

cha

rge

of

137C

s [G

Bq]

Precipitation per event [mm] Precipitation per event [mm]

So

il lo

ss [

kg]

Sakuma et al, J Enviorn Radioact (2017)

RCs distribution in soil(input data)

Air dose rate evaluation

Depth distribution of RCs in soil

Agreement of predictions with measurements

Prediction model for ground-shine dose rate 23

Malins et al, J Environ Radioact (2016)

Top soil removal 　　　　 　 Layer interchange 　　　　　　　 Reverse tillage

Remediation method

Decrement of air dose rate

Observations Simulations (center)

Topsoil removal

40 - 70% 73%

Layer interchange

- 64% 68%

Reverse tillage 30 - 60% 54%

Remediation simulations: Comparison with measurements

Change to depth distributions

Prediction of decontamination efficiencies 24

Malins et al, Health Phys (2016)