7． Conclusion
The Act on Special Measures Concerning Nuclear Emergency Preparedness of Japan (LawNo.156, 1999) stipulated that the Nuclear Emergency Response Headquarters under theCabinet Office was responsible for preventing the release of radioactive materials to theenvironment. But the concrete legal framework was not in place before the Fukushima
Daiichi Nuclear Power Station (1FNPS) accident for emergency responses to contamination
due to radioactive materials released to the public environment.
Under such circumstances, relevant government authorities including the MOE and local
governments such as Fukushima Prefecture have been engaged in large scaledecontamination works for diverse and vast areas including housing areas, public facilities,roads, farmland, forests near residential areas, etc. These works have been undertaken to
ensure public safety for facilitating early return of residents to their homes and restoration of
their daily lives. Such decontamination works are unprecedented worldwide and have been
implemented with all possible ideas, accumulated experiences and knowledge in atrial-and-error approach.
The decontamination works continue. Key experience and knowledge of significanceobtained to date are reviewed and summarized below.

（1） Fixing of legal, institutional and technical foundations
In August 2011, the Act on Special Measures Concerning the Handling of Radioactive
Pollution by the Accident at the Nuclear Power Station caused by the Great East Japan
Earthquake which occurred on March 11, 2011 (Law No. 110, 2011) (the “Act on SpecialMeasures”) was enacted in response to the 1FNPS accident. Thereafter, competent authorities
including the MOE formulated relevant ministry ordinances, standards, guidelines, etc. asneeded.
The MOE started the decontamination works under its direct jurisdiction based on theCommon Specifications provisionally formulated in a trial-and-error approach, using the thenexisting rules and mechanisms practiced by the Ministry of Land, Infrastructure andTransport (MLIT), the Ministry of Agriculture, Forestry and Fisheries (MAFF), etc. In doing
so, the MOE needed assistance from the experienced staff of MLIT and MAFF. The MOE
lacked experienced personnel for public works under its direct jurisdiction. The MOE
continued thereafter improving the Common Specifications step-by-step throughtrial-and-error in field experiences. Consequently, the whole framework of decontamination
works has been specified to a certain degree, including concrete work implementation details.
Prompt initiation of decontamination works, as needs emerged, has become possible, andquality of work has been pursued for improvement.
（2） Roles borne by the decontamination business operators in decontamination

works
There were two big requirements to implement large scale decontamination works, besides
technical competence for decontamination: one was the capacity to deliver the large amountsof equipment and human resources needed to the decontamination sites appropriately and ina timely manner, and the other was the project management capability to implement large
scale decontamination works efficiently and effectively under tight time pressures.
Especially to note in the decontamination works after the Great East Japan Earthquake in2011 was that the works had to be implemented under limited lifeline infrastructures. Under
such circumstances, it was absolutely a must to involve credible local construction industry
members for the decontamination works. They had experience and relevant technologies,
which they accumulated by quickly restoring the area after such things as severe weather
storms (e.g. typhoons and heavy snow). The decontamination business operators, whose key
players were construction companies, have been engaged in the decontamination works while
introducing non-conventional ideas by accumulating further experiences and knowledge.
Since the works which could be mechanized were limited in the decontamination works,418

large workforces were needed. But in nearby areas (especially Miyagi and Iwate Prefectures),large workforces were also in big demand for restoring the areas from the aftermaths of theearthquake and tsunami and for reconstruction. The decontamination business operators
could manage to recruit a large number of workers with the cooperation of local construction
companies, and the like. However, many of these workers were not experienced in site worksof civil engineering and construction. These workers needed education, not only technicalknowledge on decontamination or radiation protection, but also occupational safety andhealth for civil engineering and construction. Consequently, the decontamination business
operators had to spend a large amount of time and do a lot of work to provide those many
workers with education on decontamination and regular training of occupational safety andhealth.
Furthermore, the decontamination business operators often found it necessary to be very
flexible in updating the work schedules, depending on the progress: for example, acquisitionof agreement to land use for temporary material storage required before commencing
decontamination work; or its progresses at each temporary storage site did not proceed as
quickly as initially planned. The situation has been different from ordinary contracts for
public construction works, in which the order is awarded after the land use conditions, andthe like are fixed.

（3） Significance of decontamination model projects and existing technologies usedin decontamination
Soon after the accident, several pilot projects of decontamination were implemented
including “decontamination model projects” of the Cabinet Office. Such pilot decontamination
projects did not necessarily show standard decontamination models, but they certainly
brought good outcomes in identifying efficient and effective decontamination methods, andmeasures to ensure radiation workers’ safety. It was a very meaningful step toward large
scale decontamination works thereafter. The experiences and knowledge obtained from thesepilot projects have also shown that the technologies having been accumulated in theconstruction industry or their improved technologies can be effectively used indecontamination works, too, and that improvement in working procedures and management
is equally important in implementing decontamination works.
Another point to note is that accurate and efficient air-dose monitoring is needed in
evaluating the appropriateness of the decontamination works and to this end various
innovative monitoring technologies have been developed and applied, including mobile
monitoring vehicles and drone monitoring helicopters.
Further to note is that such decontamination pilot projects have also worked, not only inaccumulating technical knowledge, but in developing competent field workers with technicalknowledge. They also could facilitate the understanding of local community residents about
the decontamination works and their outcomes.

（4） Considerations in choosing decontamination methods and operation conditions
Decontamination methods to be applied, their operation conditions and the decontamination
effects depend on various environmental conditions such as site situations, material properties
or surface conditions of the objects subject to decontamination, or their aging variation withtime. Therefore, the best decontamination methods or conditions are difficult to specify
beforehand, even for a particular object to be decontaminated. For example, fordecontaminating paved road surfaces, high-pressure water cleaning was effective to someextent in the early stage, but after some time, when radioactive cesium migrated from theground surface deep into the materials, scraping of the paved road surface by shot-blasting
became a practical and effective approach, instead of cleaning the surface.
It should be noted that the decontamination effect was not the only criterion for choosing thedecontamination method and operation conditions. Construction workability as well as419

maintainability of target objects was also considered. Final selection of the decontamination
methods and conditions were made only when the consent of local residents was obtained in
the respective communities.

（5） Strengthening management for appropriate decontamination works
It was necessary to systematically fix documented work procedures, mechanisms, etc. forsmooth operation of the decontamination works, in order to implement unprecedented
large-scale decontamination works.
Nevertheless there were cases when the decontamination works not specified in theguidelines or in the Common Specifications became necessary, because the decontamination
works had been implemented under the relevant knowledge being limited. In such cases,
government supervisory personnel and the decontamination business operators jointly
worked out the appropriate procedures to apply. Some of these procedures have been
incorporated into the standard work procedures when it was deemed as being possible togeneralize them. Thus, the PDCA cycle (Plan – Do – Check – Act) has been pursued forimprovement.
In January 2013 it was reported that decontamination had been questionable in some cases.
The report was about an incident which could have damaged public trust in the community.
The MOE launched immediately the “Headquarters for Proper Decontamination Promotion” andformulated the “Appropriate Decontamination Program” consisting of three main pillars:
Thorough responsibility for decontamination works by the decontamination business
operators; Establishment of comprehensive management systems; and Strengthening of MOE
organizational settings.
Based on this “Appropriate Decontamination n Program,” emergency hotline telephone number“Decontamination Dial 110 (Hotline)” was set up at the MOE to receive information onquestionable cases of decontamination. The information received was examined for
confirming the facts and, as needed, attention of the decontamination business operators wasdrawn to the problems. Their responses to the information were disclosed on the MOE
homepage.
（6） Communication with local residents
When implementing a big undertaking like the decontamination works, sufficient time isneeded for preparation. But on the other hand, strong desires were expressed by the localresidents to initiate decontamination works at the earliest possible time. It was very
important, therefore, to establish mutual trust with the local residents through sincere
communication, in implementing decontamination works, empathy with them in mind.
In the areas such as the Special Decontamination Areas, from where residents had
evacuated, they could not witness the decontamination works by themselves. When planningdecontamination work in such areas, opportunities were arranged for them to visit the site for
their prior consent to the work or to confirm the decontamination works for themselves. For
facilitating their prior consent, significant efforts were made to sincerely respond to them byhearing and evaluating their requests, and repeating explanatory responses to their concerns.
Since the decontamination works affect the buildings, houses and land directly, priorconsent of their owners is legally required for the works. Therefore, drawings and photos wereattached as appropriate to the document of consent in order to clearly stipulate the contents
of agreement for both parties. The results of dose measurements before and after thedecontamination works were also reported using drawings, and the like to relevant parties asappropriate including the owners.

（7） Collaboration with relevant organizations and information dissemination
It was absolutely indispensable, in implementing the decontamination works, to respond to420

all kinds of concerns and dissatisfactions of local residents about the decontamination
methods and decontamination works, and concerns about safety of temporary storage sites.
The MOE cooperated with Fukushima Prefecture and set up the “Decontamination
Information Plaza,” in order to disseminate relevant information on decontamination andradiation, and to set up an activity base for experts. The Decontamination Information Plaza
has promoted communication with local communities by providing various exhibits andpamphlets, arranging workshops or opinion exchange meetings, dispatching registeredexperts to local governments or communities upon request, or responding to consultations
from the local residents. The MOE has also made efforts to facilitate people’s understanding
through operating its websites and the Call Center, and information dissemination via massmedia.
The MOE has kept close contacts with international organizations such as the IAEA inimplementing the decontamination works and in parallel promoted information sharing with
the international communities based on bilateral national cooperation agreements, and thelike.

421

This report assembled comprehensively, with key attention to the decontamination works
by the MOE, the basic policy of decontamination, its implementation framework, knowledge
about managing the decontamination works based on the actual decontamination works
experienced in the fields, and individual decontamination methods, conditions and effects
thereof. The report was compiled by the Editorial Committee, which determined its structure,contents, items to survey, division of responsibilities, etc. Its members are listed below (TheMitsubishi Research Institute, Inc. served as the secretariat).
The report has assembled the experiences and knowledge concerning decontamination ofradioactive materials in Japan, focusing on the activities of the MOE. But it is important tocollect and preserve all relevant documents and data, not only those of MOE but those ofrelevant ministries, local governments, research institutes and other related institutions, inorder to prepare for possible accidents in the future at nuclear facilities and also to contributeto the relevant research activities.

The Editorial Committee for the “Decontamination Report”
Tadashi INOUE (Chair)

Clean-up Sub-committee Chief, Atomic Energy Society of Japan
Research Advisor Emeritus, the Central Research Institute ofElectric Power Companies
Shinichi NAKAYAMA
Japan Atomic Energy Agency
Yoshitake SHIRATORI Japan Atomic Energy Agency
Shinichiro ASAZUMAJapan Atomic Energy Agency
Kazuto ENDO
National Institute for Environmental Studies
Takeshi IIMOTO
University of Tokyo
Kazuro SATO
Taisei Corporation
Yoshio OSHINO
Kajima Corporation
Ken WATANABE
Shimizu Corporation
Shoko YASHIO
Obayashi Corporation
Takahiro NAKAJIMA
Hazama Ando Corporation
Shintaro HAYASHI
Maeda Corporation
Katsuhide MORIMOTO Okumura CorporationYuichi OZUTSUMITokyo Power Technology Ltd.
Takashi TOMIOKAATOX Co., Ltd.
Takashi OHMURA
Ministry of the Environment, Government of Japan422