Overview of the Results of
the Decontamination Model Projects
Kaname Miyahara
Japan Atomic Energy Agency (JAEA)

Side Event by Government of Japan
at 56th IAEA General Conference, Sep 17, 2012

Fukushima regional contamination
Off-site contamination mainly
volatiles: initially concern focusedon shorter-lived I isotopes evacuation and restriction of
consumption of some foodstuffs
 After decay of shorter-lived
isotopes, now dominated by Cs134/-137 which is the focus forcleanup actions
 Cs tends to bind strongly tosurfaces, especially clays. Doses aregenerally low and continually
reduced by washoff / soil mixing.
Cumulate deposits of Cesium (Cs-134 and Cs-137)
estimated by MEXT
Deposits of Cs-134/Cs-137[Bq/m2]

Fukushima Dai-ichi
20㎞
30㎞
60㎞
80㎞

1Fukushima remediation overview
A wide range of focused clean-up
projects were rapidly initiated bymunicipalities and local communities
for sensitive areas (schools,playgrounds, …)
 2 small test projects were initiated by
JAEA in August: development andtesting of technology (ended inMarch) Further technology demonstrations
initiated in November in 11
municipalities, including those in theevacuation zone (ended in July) Parallel tests of novel
decontamination technology (25proposals funded) have been
completed Regional decontamination ispresently being initiated

22

Main Challenges for Implementation of Full-scale Decontamination
Which methods are appropriate?

What are the points to check when supervisingdecontamination work? What know-how should be
used for decontamination work?

Is it possible to apply new technology?

What are the points to consider when preparing
plans and ordering decontaminationequipment/services?

There was little organised
quantitative information based on
actual data (cleanup effectiveness,costs, volumes of wastes generated,etc.) that could be used whenselecting between various alternatives
for decontamination, waste transportand storage methods
 There was little documented guidanceon decontamination for local
governments, local residents andprivate sector companies on how toorder decontaminationequipment/services
 Possibilities of development andupgrading of new decontamination
technologies had not been examined

3

Implementation Scheme for the Decontamination Model Projects
National government (Cabinet Office)Target Municipalities

Commissioning

Public callfor proposals

Headquarters ofFukushima Partnership Operations,Japan Atomic Energy Agency

Date City

Dose rateclassification

Soma City

Less than 5mSv/yFukushima
City

Kusano area
Base of “Patrol Team for
IitateVillagethe Entire Iitate Village”
Planned evacuation area

Municipality Group A: Taisei JV(Minami Soma City, Kawamata Town,Namie Town, Iitate Village)

KawamataTown

Sakashita area

Minami Soma City

Nihonmatsu City

Municipality Group B: Kajima JV(Tamura City, Futaba Town, Tomioka Town,
Katsurao Village)

Restricted Area

Tsushima area

Kanefusa Elementary Schooland surrounding area
Katsurao Village

Katsurao Municipal Officeand surrounding area

Municipality Group C: Obayashi JV(Hirono Town, Okuma Town, Naraha Town,Kawauchi Village)

 Public call for proposals: Proposals for complete cleanup:
including planning, decontamination and evaluation
stages were submitted by Joint Ventures (JVs). The 3 JVs
shown above were selected after an examination* byJAEA.
 Implementation scheme: Each JV implemented itsproposed technological activities and JAEA managed,supervised and evaluated the overall program.
 Target municipalities: Eleven municipalities in evacuatedareas Sizes of the decontamination target areas: approx. 20ha
per target municipality
 Total manpower effort for the model projects (excludingemployees of JAEA): approx. 87,000 person-days

Namie Town

Futaba Town

Tamura City
MiharuTown

Gongendo area

Jikenjo area

Okuma Municipal
Office andsurrounding area

Fukushima Daiichi
Nuclear Power Station

Ottozawa area

Okuma Town

Tomioka Daini Junior High SchoolOno Town

Yonomori Park

Tomioka Town

KawauchiVillage

Koriyama
City

Kainosaka area
Kamishigeoka area
Naraha Town

Restricted Area
PlannedEvacuation Area
Decontamination
Model Project
implementation areas

Minami Industrial Complex
Iwaki City

Hirono Town

Chuo-dai/Nawashirogae area

Futaba Town has advised us that they would not join theDecontamination Model Project as a target area.

* An examination conducted by a committee appointed by JAEA4

Activities within the Decontamination Model Projects

Preliminary remediation
planning
Municipality
guidelines

Environmental
Ministry guidelines

Radiation survey before
remediation
Decontamination
Catalogs

Establish tailored remediation implementation plan

Apply remedial measures

Evaluate effectiveness of remedial measures,
Review effectiveness and assess input for
remediation guidelines

Updating of
Decontamination
Catalogs based on
the results of theapplication ofcleanup methods

Utilisation as real-world examples (presented in the form ofguidelines, manuals, etc.) that can be used as a source ofreference by the national government, local governments,
local residents and private sector companies when
performing regional decontamination5

Site characterisation
Measurement approaches involved
modification of existing technology
and development of new methods
When linked to appropriate dataloggers, these provided rapid anduser-friendly maps of radionuclide
distributions

6

Data interpretation & synthesis


Maps were particularly useful to guide
remediation planning
Depth profiles allowed assessment of benefitsof different soil remediation approaches
Options could be assessed using a model topredict effective dose reduction
Relative concentration
存在比率μSv/h(μSv/h)

μSv/h(μSv/h)

3.0

3.0

2.25

2.25

Depth (cm)

深度（ｃｍ）
00.2

1 cm pitch

2～34～5
5～102

Result of calculation
the predicted
air dose rates
Dose rateofafter
clean-up(at 1 m) after decontamination

based on a model prediction

0.0

Depth (mm)ResultDoseof calculationof the air
dose rates
rate before
clean-up(at 1 m) from simplified monitoring
based
on monitoring
results
beforedecontamination(by JAEA)

深度（ｍｍ）
00.75

0.00.85 cm pitch

N=48

Schools and playing fields

1.5

0.75

0.60～115～20
1.5

0.4

0～1
1～2
2～3
3～4
4～5
5～6
6～7

Relative concentration
存在比率
0.2

0.4

0.6

0.8

1

N=9

Dense-graded pavements

7

Clean-up technology


Although the majority of the effort involved
manual washing and contaminated material
removal using conventional technology,
methods that might improve decontamination
while decreasing volumes of waste were tested
Radiation dose of clean-up workers was strictly
controlled and always remained low (within thespecified upper dose limit)

8

Scheduling of Decontamination
Forest decontamination

Farmland decontamination

Decontamination of playing fields and large buildings

Decontamination of residential houses

Decontamination of roads

9

Clean-up of Trees and Forest

clipping

removing and replacing
hotspot soil

removing humus layer

clipping

water jet10Clean-up of Farmland turf stripping

 ploughing topsoil removal

fixation1111

Clean-up of Buildings

Pressure washing roofs

Cleaning gutters

Wiping and grinding roofs

Removing drainage hotspots
Stripping roof surfaces
12Clean-up of Paving and Surfaces
 high pressure waterroad cleaner

 surface stripping blasting

Iron shot blasting

Ice blasting13

Waste handling

Waste was reduced in volume to the maximum extent
possible – e.g. grinding / chipping of foliage,
concentration of radioactivity from contaminatedwater, separation of waste by activity level,…
In most cases, labelled heavy-duty flexible containers
were used for solid waste transportation and storage
Containing flesh soil toprovide shielding

Container-by-container
management
ICタグによる個別管理
using IC tags
Location
場所Date
日時Type
種別
線量Dose...…

A-1 B23-C
A-1
B23-C
11/10/01 121211/10/01
Mud泥土
500Bq/kg
500 Bq/kg…
...

An example of IC tag
ICタグの例
除去物をフレコンバッグ（フレキシブルコンテナバッグ）に詰める

メタルタグ付
・除染日時
・除染場所
・内容物

Waste

Measurement of surface dose rates ofdecontamination waste in the shielding zone

トレーサビリティを確保
An
example of metal tag
メタルタグの例
搬送時・仮置き時の飛散防止

Anペーパータグの例
example of paper tag

仮置き場からの搬出作業を容易にする
Management of decontamination waste information (tags)
14

Waste Management


Locations for temporary storage sites were selectedtaking into consideration topography, land use
status, available areas of land, local government
requests, etc., following checks that safety can beensured
A range of different approaches were used for
temporary storage of waste on the surface or inshallow pits

Above ground storage type (on flat ground)

Above ground storage type (on slopes)

Underground storage typeSemi-underground storage type15

Results of Dose Reduction by Wide Area Decontamination[Example Tomioka Town (Yonomori Park area, 9 ha)]Dose rate after clean-up

Decontamination

Dose rate before clean-up

Decontamination
target area
Dose rate before clean-up (mean μSv/h)

Dose rate after clean-up (mean μSv/h)

Dose reduction(%)

Residential area

8450

Large buildings

9550

Playing field

11280

Roads

9540

Forests

10460

Outside the decontamination target
area

8710

Land use status

16

Results of Dose Reduction by Wide Area Decontamination
Estimated annual dose reduced to less than 20 mSv/y, for areas
with 20 – 30 mSv/y before decontamination

Estimated annual dose could not be reduced below 20 mSv/y, forareas exceeding 40 mSv/y before decontamination

In case of agricultural and residential area of Ottozawa, Ohkuma,
the dose rate reduced by 70 %. However, estimated annual dose
could not be reduced below 50 mSv/y

The fractional dose rate reduction was smaller in areas ofrelatively low dose rate, compared with high dose rate areas

17

Status and Lessons Learned
The decontamination model projects have provided:
 Experience and tools for planning and coordinating efficient,safe and cost-effective remediation programmes
 Evaluation of the applicability of remediation technology
with an assessment of the pros and cons of different
approaches
 Guidelines for tailoring of projects to the conditions found indifferent sites
 Practical experience has shown that stakeholder involvement in
implementation of clean-up activities is essential
 Material for explaining remediation to stakeholders andproviding the basis for establishing dialogue with them has
been developed

18

A look to the future
During future remediation:
 Experience can be used to constantly update the cleanup
knowledge base with the intent of continuous improvementof methodology and toolkits
 An advanced communication platform can be implemented
to facilitate information exchange between all those
involved and, in particular , encourage dialogue with local
communities and their involvement in decision-making
 Waste management will be a special focus for R&D to
support optimisation in terms of both volume reduction andeasing / increasing safety of temporary storage, interim
storage and eventual final disposal The regional work will: Allow displaced populations to return home to normal
lifestyles as quickly as possible
 Provide the knowledge and experience needed for later
decontamination of the Fukushima Dai-ichi site.
19