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Challenges for Enhancing
Fukushima Environmental Resilience
Kaname MIYAHARA, Kimiaki SAITO Fukushima Environmental Safety Center
Japan Atomic Energy Agency (JAEA)IAEA Technical Meeting on Remediation Techniques and Strategies in
Post-Accident Situations
13-17 June 2016, IAEA Headquarters, Vienna, Austria
1
Fukushima Regional Contamination� Initially concern focused on short-
lived iodine and other isotopes in
addition to radiocesium
� evacuation and restriction of
consumption of some foodstuffs
� After decay of short-lived isotopes,
now dominated by 134Cs/137Cs which
is the focus for off-site clean-up
actions
� Cs tends to bind strongly to soil
surface, especially clay
� Exposure doses of inhabitants are
mainly from external exposures,
generally not high, and have
continually reduced by decay of Cs,
washoff / soil mixing2
Protective Actions
Designation of evacuation areas was
completed just after the accident
(Apr. 22, 2011)Specific Spots
Recommended for
Evacuation
3
Rapidly expanded
(3-km, 10-km, 20-km
radius by Mar. 12)20km
Evacuation Order Areas
� Regulatory limits for
contaminated food and
water based on
�<5 mSv/y (March 20, 2011)
�<1 mSv/y (April 1, 2012)
Category Limit (Bq/kg)
Drinking water 10
Milk 50
General Foods 100
Infant Foods 50
Food and water restrictions
Switched from
distance to a
threshold
radiation dose of
20 mSv/y on Apr.
22
Remedial Management Options
(i) external doses from surfaces contaminated by
deposited radionuclides;
� Currently, the dominant pathway of public
exposure
(ii) ingestion doses from the consumption of
contaminated foodstuffs and drinking water;
�Strict Food Restrictions; Government
restrictions put into place after the Fukushima
Daiichi accident kept most contaminated
foodstuffs off of the market (IAEA, 2011)
(iii) inhalation doses from resuspended material
� This route of exposure is of less significance and
not considered further (UNSCEAR, 2013)
� Decontamination (cleanup)*
� Restrictions on access to highly
contaminated areas (such as the
outer 20 m borders of forests
adjacent to settlements )
� Other measures relevant for
individual lifestyle (e.g. commute
route change) based on the
personal dose data and
understanding Cs behaviors in the
environment
* Dilution methods for soils such as plowing are
included
To reduce external doses
4
Management options are designed to
reduce:
Decontamination Pilot Project (DPP) by JAEA� JAEA was chosen by the Government to conduct
decontamination pilot projects (DPP) at 16 model sites in
11 municipalities, including evacuation order areas (Sept.
2011~June 2012)
� Main challenges to implement full-scale decontamination
were lack of both real-world examples and also
experience for planning and implementing
decontamination technology appropriate to Japanese
boundary conditions
� Therefore, the decontamination pilot projects played a
key role to support drafting of guidelines and manuals
that can be used by the national government and local
municipalities to optimize regional remediation work
� Check the availability and efficacy of proven and new
techniques
� Investigate cost, work period, workforce, waste
generated, and radiation exposure of workers
� Establish waste management including volume
reduction of wastes and treatment of the secondary
waste
� Secure workers’ safety under radiation protection
� Establish optimal radiation monitoring
� Record the public communication* An examination conducted by a committee appointed by JAEA
Date City
Fukushima
City
Kusano area
Iitate
Village
Planned evacuation area
Soma CityDose rate
classification
Less than 5mSv/y
Kawamata
Town
Nihonmatsu City
Sakashita area
Tsushima area
Katsurao Municipal Office
and surrounding area
Katsurao Village
Tamura City
Miharu
Town
Koriyama
City
Ono Town
Minami Soma City
Restricted Area
Kanabusa Elementary School
and surrounding area
Gongendo areaNamie Town
Futaba Town
Jikenjo area
Kawauchi
Village
Okuma Town
Tomioka Daini Junior High SchoolTomioka Town
Fukushima
Dai-ichi
Yonomori Park
Kamishigeoka area
Naraha Town
Minami Industrial Complex
Hirono Town
Futaba Town has advised us that they would not join the Decontamination
Model Project as a target area.
Kainosaka area
Restricted Area
DeliberateEvacuation Area
Decontamination Pilot Project implementation areas
Ottozawa area
Chuo-dai/Nawashirogae areaIwaki City
Base of “Patrol Team for
the Entire Iitate Village”
Okuma Municipal
Office and
surrounding area
Target Municipalities
5
Recommended Clean-up Technologies
◎：highly effective， ○：effective， △：moderately effective， ▲：limited effect
Land use classification Comprehensive evaluation
Forest
◎Removal of leaf litter and humus layers (on flat ground and slopes), 〇Removal of leaf litter, humus
layers and topsoil (on flat ground), ▲Trunk washing, 〇Branch trimming in the lower part (evergreen
tree)
Farmland
◎Machine that strips off surface of soils, 〇Backhoe (stripping off depth of 5 cm of the soil),
◎Reversal tillage (by tractor and plough), 〇Ploughing to replace surface soil with subsoil (by
backhoe)
Residential
area
Roof ▲High pressure water, 〇Brushing, 〇Wiping, ▲Apply a remover
Gutter �High pressure water, 〇Wiping
Wall 〇Brushing
Topsoil 〇Removal of topsoil
Rubble 〇Washing of the rubble, 〇Removal of the rubble
Turf 〇Removal of the Turf
Garden tree ▲Clipping a garden tree
Interlocking block �High pressure water
Large
structure
Concrete and Mortar surface�Sanding machine with the dust-collection (Plane which scrapes concrete), 〇Ultrahigh pressure
water (Over 150MPa), 〇High pressure water (10-20MPa), 〇Iron shot blasting
Roof
floor
Concrete surface 〇High pressure water (including brushing)
Waterproof coating surface 〇High pressure water (including brushing)
Downpipe 〇High pressure water(Maximum 50MPa)
Playing field〇Strips off surface of soils (Large mower+Sweeper), 〇Strips off surface of soils (Road planers), 〇
Strips off surface of soils(Motor grader), 〇Ploughing to replace surface soil with subsoil
Swimming pool 〇High pressure water
Turf 〇Turf stripper
Paved road
▲Road cleaners + Riding style road sweepers, �High pressure water (About 15MPa)+Brushing, �Car
of a functional recovery drainage pavement, 〇Ultrahigh pressure water (120～240MPa),○Iron shot
blasting, ○TS Road planers
6http://dx.doi.org/10.11484/jaea-review-2014-051
Accident Recovery�The Act on Special Measures Concerning the
Handling of Radioactive Pollution (August
2011)
� Special decontamination areas; the Restricted Area + the
Deliberate Evacuation Area
�Further subdivided into three areas (August 2013)
• Area 1: <20 mSv “ready to be lifted”
• Area 2: 20-50 mSv ordered to remain evacuated
• Area 3: >50 mSv not expected to drop below 20 mSv/y
within 5 years
� Intensive contamination survey areas; all other
contaminated areas (1 mSv/y ~20 mSv)
�Decontamination of these areas involves the
cleaning of structures and removal of
contaminated soil
�Removed soil and other contaminated wastes
are being stored at remediation locations or at
temporary sites
�Contaminated soil and waste are to be
gathered and placed into interim storage
facilities until transferred to a long-term
disposal site outside of the Fukushima area
Principles set by ICRP
Emergency exposure situation
Existing exposure situation
Long-term objectives
Additional dose to be
1 mSv/y
100 mSv/y
20 mSv/y
1 mSv/y
Aiming at 20 mSv/y or
less
7
The national government
implements
decontamination work
Special decontamination areas
Municipalities
implement
decontamination work
funded by the
government
Intensive contamination
survey areas
Waste Management Challenges
� Clean-up efforts are generating
huge volumes of contaminated
soil and waste, which must be
managed in a safe and cost-
effective manner, wherever
possible implementing waste
volume reduction
� Future reuse of soil for
construction purposes is an
important option, if constraints
in terms of allowable organic
and clay content can be
managed
Below
8kBq/kg
Over
8kBq/kg
below
100kBq/kg
Over
100kBq/kgIncinerated
ash over
100kBq/kg
Waste in
countermeasure
area over
100kBq/kg
5
10
0
10.06Mm3
10.35Mm3
0.01Mm3
1.55Mm3
0.02Mm3
Contaminated soil and wastes
Vo
lum
e (
Mm
3)
Contaminated soil
and wastes
Incinerated ash
16~22 Mm3
current estimation
Wet particle-size
separation
Chemical
treatment
Heat treatment
8
Soils & wastes
Cs removed or
reduced materials Reuse
Volume Reduction
Cs accumulated
materialsFinal disposal
9
Current Status避難指示区域
(2011年11月25日)
Lifted on April
1, 2014
Lifted on
Oct. 1, 2014
Lifted on
Sept. 5, 2015
Various situations exist
* Exposure dose reduced to the evacuation standard of 20 mSv
y-1 or less
not expected to drop below 20 mSv/y within 5 years
ordered to remain evacuated
ready to be lifted
� Areas where people regain ordinary daily life
� Areas where the evacuation order was lifted*
� Areas where the evacuation order will be
lifted no later than March 2017
� Areas where the prospects for lifting the
evacuation orders are not in sight
Evacuation order areas
(2015/9/5)
10
How to Enhance Fukushima Environmental Resilience
�Address the needs for better scientific and
technological capabilities to assess, predict, and
minimize the impact of radiological
contamination
�Enhance the understanding of radiation and
associated risks in the public
Kai Vetter, 2015
The concept of Resilience；
The ability to recover from or more successfully adapt to adverse events
Regional scale distribution Deposition of
Radiocaesium [Bq/m2]
River/Floodplain
Dam
11
Individual external
doses in living areas
Development of a Technical Basis
for Enhancing Fukushima Environmental Resilience
Transport and accumulation
in a river basin
Forest
12
Evolution of Air Dose Rate Distribution
Dose rate maps derived from car-
borne surveys
� Analysis of repeated survey results clarified the trends in air dose rate reduction for different
conditions due to radioactive decay, decontamination and natural weathering processes
Elapsed me since June 2011
Avera
ge a
ir d
ose r
ate
(r
ela
tive)
0 400 800 1200 1600
1.0
0.1
2
5
Physical decay &
Forest
Flat fields
Roads
(car survey)
� An empirical approach was employed to predict the dose rate distribution based on statistical
analyses of large-scale environmental monitoring data accumulates since the accident
� The time-dependent decrease of air dose rate in any specific setting can be approximated by a
combination of two exponential functions, representing “fast” and “slow” reduction rates
� Analysis linked to geostatistical data shows that the air dose rate reduction clearly depends on land
use
Elapsed time after the accident（y）
5 years after 30 years after
13
Air
do
se r
ate
（re
lati
ve）
0.1 1 3 5 10 15 300.005
0.01
0.1
1
3Evacuated zone(20-50 µSv/y)except forests
Air dose rate（µSv h-1)
Air dose rate（µSv h-1)
0.2
1
10
50
1
10
50
0.2
Development of a Predictive Model
by an Empirical Approach
14
Empirical Prediction of Air Dose Rate Distribution
air dose rate
（μSv/h)
air dose rate
（μSv/h)
Corresponding to the
evacuation standard of 20
µSv y-1*
*based on the assumption that people spend 8
hours a day outdoors and 16 hours a day indoors,
for the latter considering a dose reduction factor of
0.4
3.8 3.8
After 5 y After 30 y
� Area more than 3.8 µSv/h will decrease in 30 years after to as much as 5% of such area
in 5 years after the accident.
Regional scale distribution Deposition of
Radiocaesium [Bq/m2]
River/Floodplain
Dam
15
Individual external
doses in living areas
Transport and accumulation
in a river basin
Forest
Development of a Technical Basis
for Enhancing Fukushima Environmental Resilience
16
Natural Processes Causing Mobilazation of Radiocaesium
Transport /
accumulation in
a river system
Transport
by ocean
currents
transport from
tree crowns to litter
removal of
runoff
removal of
litter/soil by
runoff
Normal flow conditions During heavy rainfall
Cs tends to bind strongly to surface soil, especially clay
Soil loss by runoff
Deposition of Cs-loaded
suspended particles
17
Cs Transport in the Forest
0
5
10
15
20
25
30
2013
/4/1
2013
/5/2
1
2013
/7/1
0
2013
/8/2
9
2013
/10/
18
2013
/12/
7
2014
/1/2
6
2014
/3/1
7
2014
/5/6
2014
/6/2
5
2014
/8/1
4
2014
/10/
3
放射
性セ
シウ
ム濃
度(B
q/L)
2013－2014年度
KA-1 Cs-134
Cs-137
Evolution of Cs concentration in stemflow (Bq/L)
Evolution of cumulative Cs due to transport
from tree crowns to forest floor
Throughfall Stemflow
Fallen leavesFY 2014
Fallenleaves
Stemflow
Throughfall
Cu
mu
lati
ve
am
ou
nt
of
13
7C
s (k
Bq
/m2)
Elapsed time after the accident（d）
0
60
120
180
100 500 1000 1300 0
10
20
30C
s co
nce
ntr
ati
on
(B
q/L
)
Mature Japanese cedar
137Cs 134Cs
Japanese cedar forest in Kawauchi village
� Currently, most of Cs deposited on tree
crowns has transported to forest floor
(Onda et al., 2016)
A: Erosion rate of surface
soil
4.9
kg/3months
B: 137Cs concentration
in eroded soil64 kBq/kg
C: 137Cs transport rate by
erosion[A×B×4 / 54,000 m2]
0.023
kBq/m2/y
Cs Transport from Forest Areas by Runoff
A: Erosion rate of surface soi 0.012 kg/m2/y
B: 137Cs concentration in
eroded soil16 kBq/kg
C: 137Cs transport rate by
erosion (A×B)0.19 kBq/m2/y
D: 137Cs deposition in surface
soil770 kBq/m2
Ratio of annual 137Cs loss to 137Cs deposition in surface
soil (C/D)
0.03%/y
Measurement of accumulated 137Cs in
stream sediments in Kawauchi Village
(2014/6/27～ 2014/9/30)
Measurement at a monitoring plot in
Kawauchi village
（2013/11/19 ～2014/10/20）
A monitoring plot to
measure erosion rates of
surface soil137Cs transport rate by
erosion1.2 kBq/m2/y
Ratio of annual 137Cs loss to 137Cs deposition in surface
soil
0.15%/y
（FY 2013）
18
137Cs transport rates by surface-soil erosion
A sampling point of stream sediments
19
1.2 0.7 1.5 3.6
18.5
32.9
0.4
5.8
22.0
0
10
20
30
40
50
60
2 (0.6) 11 (1.4) 16 (1.8)
土砂
濃度
(mg
/L)
流量(m3/s) (水位 (m))
>60 um
3-60 um
0.45-3 um
Flow rate (m3/s)
(Water level (m))
13
7C
s co
nce
ntr
ati
on
water flow 2 m3/s 16 m3/s
Dissolved 137Cs (A) 0.3 Bq/L 0.3 Bq/L
Particulate-bound 137Cs (B)
0.1 Bq/L 2.2 Bq/L
(A)+(B) 0.6 Bq/L 3.3 Bq/L
Normal flow High river flow
Co
nce
ntr
ati
on
of
susp
en
de
d s
ub
sta
nce
s (m
g/L
)Cs Transport by River Flow
(dissolved/particulate-bound Cs)
Ukedo riv.
Takase riv.
Ogaki dam
0
20
40
60
80
0 200 400 600 800 1,000
De
pth
（cm
）
Activity conc. （kBq/kg）St.2
134Cs
137Cs
134+137Cs
0
20
40
60
80
0 200 400 600 800 1,000
De
pth
（cm
）
Activity conc. （kBq/kg）St.5
134Cs
137Cs
134+137Cs
0
20
40
60
80
0 500 1,000 1,500 2,000
De
pth
（cm
）
Activity conc.（kBq/kg）St.7
134Cs
137Cs
134+137Cs
Simulation of Sediment inflow
due to a flood event
(Deposition of sand, silt, and clay
120 hr after the event) Observed Cs concentration in the
sediment of dam lake
20
Sand
Silt
Clay
Cs Accumulation in the Sediment of Dam Lake
Water levelElevation: 140 m(Current water level)
Elevation: 170 m*
Ratio of silt outflow 4.5% 1.6%
Ratio of clay outflow 54% 34%
Ratio of 137Cs outflow 9.0% 3.5%
Ratio of silt-bound 137Cs 40% 18%
Ratio of clay-bound 137Cs 60% 82%
More than 90% of inflow sediment and 137Cs deposited in
the reservoir during and after heavy rainfall events
*Operational water level before the accidents
Measured
Simulated
Concentration of 137Cs in Flow
at the exit of the reservoir
Co
nce
ntr
ati
on
of
13
7C
s (B
q/L
)
Ogaki dam
St.2
St.5
St.7
Overview of 137Cs Flux from Each Catchment of
Ukedo River Basin
Total flux
to the
ocean
1 TBq/y
Ogaki-dam outflow
0.07 TBq/y
Ukedo riv.
Takase riv.
3 km
More than 90% of radiocaesium flowing into the Ogaki
dam lake was sedimented in the lake
Annual transport rate of 137Cs of the forest topsoil is
around 0.1%
21Inventory Discharge
Recovery of the Coastal Marine Environment
Fisheries Agency of Japan (2015)
22
0
0.2
0.4
0.6
0.8
1
0
500
1000
1500
2000
2500
3000
グラフ タイトル
系列1 系列2 系列3
500
1000
1500
2000
2500
3000
0
20
40
60
80
100
0Oct.-Dec.
Jul.-Sep. Jan.-Mar. Oct.-Dec. Apr.-Jun.
Jul.-Sep. Jan.-Mar. Oct.-Dec. Apr.-Jun.
Jul.-Sep. Jan.-Mar. Apr.-Jun.
Excess ratio %Number of samples
>100Bq/kg
<100Bq/kg
Excess ratio
Jul.-Sep.
2012 20142011 2013
Oct.-Dec. Jan.-Mar.
Apr.-Jun. Jul.-Sep.
Oct.-Dec. Jan.-Feb.
Apr.-Jun.
2015 2016
**Otosaka and Kobayashi (2013) + Updated
Statistics on fish samples
Regional scale distribution Deposition of
Radiocaesium [Bq/m2]
River/Floodplain
Dam
23
Individual external
doses in living areas
Transport and accumulation
in a river basin
Forest
Development of a Technical Basis
for Enhancing Fukushima Environmental Resilience
24
• Currently applied simple method
results in larger uncertainties.
• D(p) and t(p) are not realistically
considered in estimate.
Individual doses estimated from air dose rates
�Amount of time spent indoors or
outdoors depending on occupation
�Variations in working places
depending on the type and location
of work
�Distribution of Cs deposition
on the surface (ground,
pavement etc.)
�Weathering effects
Outdoors (Location-specific
external exposure)
Difference of lifestyleIndoors
D(p) varies according to locationt(p) varies according to individual
pavement ground
E = Σ c•D(p)•t(p)
E : total effective dose
C : conversion coefficient from air dose to effective dose
D(p) : air dose rate at location p
t(p) : residence time at location p
�Dose reduction factor
depending on house
type and surrounding
conditions
25
Measurement of air dose rates according to
the individual’s daily route
� Communicate with evacuees who wish to return to their homes
Detailed data
acquisition by interview
to know how much time
will be spent along
individual’s daily route
after evacuees return to
their homes
Man-borne survey
Realistic estimates of Individual doses
経路/場所ID 地点(部屋) 移動手段 開始時刻 終了時刻
1 自宅(寝室) 0:00 5:30
2 自宅(リビング) 5:30 8:00
3 徒歩 8:00 8:05
4 裏山 8:05 11:55
3 徒歩 11:55 12:00
2 自宅(リビング) 12:00 13:00
5 徒歩 13:00 13:05
6 畑 13:05 13:50
7 徒歩 13:50 14:00
8 畑 14:00 14:50
7 徒歩 14:50 15:00
2 自宅(リビング) 15:00 16:00
9 車 16:00 16:10
10 銭湯 16:10 17:50
9 車 17:50 18:00
2 自宅 18:00 0:00
Interview to evacuees
Realistic estimates of individual doses according to individual’s daily route
IndoorField 1
Field 2
Estimated external cumulative radiation doses
Air
do
se r
ate
(μ
Sv
/h)
Time Walking on roadsHill
Knowledge and experience gained for Enhancing
Fukushima Environmental Resilience
26
�Cleanup Navihttp://c-navi.jaea.go.jp/en/The Cleanup-navi Communication Platform provides an overview of regional contamination due to the accident and approaches to
remediation. It also includes background information on the nature of ionising radiation and its health effects to allow the user to make informed judgements as to the value of the remediation actions that are being undertaken.
�DPP reports http://fukushima.jaea.go.jp/english/outline/20150327.htmlPart 1 summarises the Decontamination Pilot Project, providing the background required to put this work in context for
an international audience. In Part 2, the subsequent application of output from this project to regional remediation is discussed, along with a status update on such work (including radioactivity monitoring), an overview of JAEA’s associated R&D and international input to / review of regional environmental decontamination in Fukushima.
� Lessons learned report http://fukushima.jaea.go.jp/english/outline/20150327.htmlThis report provides a concise overview of knowledge and experience gained from the activities for environmental
remediation after the Fukushima Daiichi accident. It is specifically tailored for international use, to establish or refine the technical basis for strategic, off-site response to nuclear incidents.
Thank you for your attention
