Fukushima Daiichi Nuclear Power
Plant Accident, Ten Years On
Progress, Lessons and Challenges

NE A

Fukushima Daiichi Nuclear Power
Plant Accident, Ten Years On:
Progress, Lessons and Challenges© OECD 2021
NEA No. 7558

NUCLEAR ENERGY AGENCY
ORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENTORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENTThe OECD is a unique forum where the governments of 37 democracies work together to address the
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The OECD member countries are: Australia, Austria, Belgium, Canada, Chile, Colombia, Costa Rica, theCzech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Israel,
Italy, Japan, Korea, Latvia, Lithuania, Luxembourg, Mexico, the Netherlands, New Zealand, Norway, Poland,
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The opinions expressed and arguments employed herein do not necessarily reflect the official
views of the member countries of the OECD or its Nuclear Energy Agency.

NUCLEAR ENERGY AGENCYThe OECD Nuclear Energy Agency (NEA) was established on 1 February 1958. Current NEA membershipconsists of 34 countries: Argentina, Australia, Austria, Belgium, Bulgaria, Canada, the Czech Republic,
Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Korea, Luxembourg,
Mexico, the Netherlands, Norway, Poland, Portugal, Romania, Russia, the Slovak Republic, Slovenia, Spain,
Sweden, Switzerland, Turkey, the United Kingdom and the United States. The European Commission and theInternational Atomic Energy Agency also take part in the work of the Agency.
The mission of the NEA is:–	
to assist its member countries in maintaining and further developing, through international
co-operation, the scientific, technological and legal bases required for a safe, environmentally soundand economical use of nuclear energy for peaceful purposes;–	to provide authoritative assessments and to forge common understandings on key issues as input togovernment decisions on nuclear energy policy and to broader OECD analyses in areas such as energy
and the sustainable development of low-carbon economies.
Specific areas of competence of the NEA include the safety and regulation of nuclear activities, radioactive
waste management and decommissioning, radiological protection, nuclear science, economic and technicalanalyses of the nuclear fuel cycle, nuclear law and liability, and public information. The NEA Data Bank
provides nuclear data and computer program services for participating countries.

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territory, to the delimitation of international frontiers and boundaries and to the name of any territory, city or area.
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Cover photo: Street planted with cherry trees in the Yonomori district of Tomioka Town (Tomioka Town City Council).

FOREWORD

ForewordT

he purpose of the OECD Nuclear Energy Agency (NEA) is to foster co-operation among its member
countries and many partners around the world to advance policy, safety, technology, and science
related to nuclear technology. The NEA serves as a forum for sharing and analysing information andexperience; supports the development and maintenance of knowledge and the development of humanresource capacities; and provides policy analyses relevant to nuclear energy. The NEA has supported
its members in understanding and responding to new developments in the nuclear field for morethan 60 years. Typically, this work involves addressing changes in technology and policy; and often it
involves absorbing operating experiences related to nuclear facilities around the world. The 11 March2011 accident at the Fukushima Daiichi Nuclear Power Plant is but one example, but it is an experience
with significant global policy and regulatory impact.
The NEA published reports on the accident in 2013 (The Fukushima Daiichi Nuclear Power Plant
Accident: OECD/NEA Nuclear Safety Response and Lessons Learnt) and in 2016 (Five Years after the
Fukushima Daiichi Accident: Nuclear Safety Improvements and Lessons Learnt). Those mainly discuss safety
improvements and legal matters. This new report covers more comprehensively the effects of theaccident and future perspectives. It provides information about the achievements of the international
community and the NEA, gives analyses on current challenges and suggests future activities ofinternational programmes of co-operation. As the work of decommissioning the power station andremediating radiological effects and socio-economic impacts on the affected areas continues, there aremany areas for international communities to learn, assist Japan and support each other.
This report is intended to provide clear information to policy makers involved in providing clean
energy, a clean environment and healthy societies through the peaceful use of nuclear energy, as wellas any member of the general public wishing to engage and understand the accident and its aftermath.

William D. Magwood, IV
Director-General
Nuclear Energy Agency

FUKUSHIMA DAIICHI NUCLEAR POWER PLANT ACCIDENT, TEN YEARS ON: PROGRESS, LESSONS AND CHALLENGES, NEA No. 7558, © OECD 2021

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ACKNOWLEDGEMENTS

AcknowledgementsT

his report was prepared under the overall guidance of Mr William D. Magwood IV, Director-Generalof the Nuclear Energy Agency (NEA).

The NEA wishes to express its gratitude to the following principal authors of the contents of thisreport: Dr Len Creswell (United Kingdom), Dr Randall Gauntt (United States), Mr Victor M. McCree (UnitedStates) and Dr Mike Weightman (United Kingdom).
The NEA team of experts was led by Mr Nobuhiro Muroya, NEA Deputy Director-General, with
contributions from Mr Shin Morita, Senior Advisor to the NEA Deputy Director-General, Ms Yeonhee Hah,
Head of the Division of Radiological Protection and Human Aspects of Nuclear Safety (RP-HANS),
Ms Ximena Vásquez-Maignan, Head of the Office of Legal Counsel (OLC), Dr Tatiana Ivanova, Head of
the Division of Nuclear Science (SCI), Ms Véronique Rouyer, Head of the Nuclear Safety Technology
and Regulation Division (SAF), Ms Rebecca Tadesse, Head of the Radioactive Waste Management
Division (RWMD), Dr Edward Lazo, Deputy Head of RP-HANS, Mr Andrew White, Deputy Headof SAF, Dr Jacqueline Garnier-Laplace, Deputy Head of RP-HANS, Dr Martin Brandauer (RWMD),
Dr Didier Jacquemain (SAF), Ms Florence Maher (RP-HANS) and Dr Yuji Kumagai (SAF). Ms Claire Mays and
Ms Valentine Poumadère served as editors of the final version. Mr Laurie Moore, Ms Elisabeth Villoutreix
and Ms Fabienne Vuillaume (Central Secretariat) were in charge of the production and layout of the report.
The NEA also wishes to thank the following senior experts and nuclear leaders from around theworld for their valuable insights and the generous time they spent in discussions with the team:
Dr George Apostolakis (Head, Nuclear Risk Research Center of Japan [NRRC]), Dr Nobuhiko Ban(Commissioner of the Nuclear Regulation Authority of Japan [NRA] and Chair of the Working Group on
Safety Culture of the Committee on Nuclear Regulatory Activities [CNRA]), Mr Michael Boyd (Director of
the Center for Science and Technology in the US Environmental Protection Agency’s Radiation Protection
Division and Former Chair of the Committee on Radiological Protection and Public Health [CRPPH]),
Dr Claire Cousins (Chair of International Commission on Radiological Protection), Mr Roland DussartDesart (Retired Head of the Legal Service of the Belgian Ministry of Economy and Chair of the Nuclear
Law Committee), Dr Toyoshi Fuketa (Chair of NRA), Mr Taro Hokugo (Director for Atomic Energy andInternational Affairs Bureau of Science, Technology and Innovation, Government of Japan Cabinet Officeand Nuclear Law Committee Bureau member), Mr Toshio Kodama (President of Japan Atomic Energy
Agency), Mr Tom Mitchell (Chair of the World Association of Nuclear Operators), Mr Ho Nieh (US Nuclear
Regulatory Commission and Former Head of NEA SAF), Dr Jean Christophe Niel (Director General of theInstitute for Radiological Protection and Nuclear Safety of France and Chair of the Committee on Safetyof Nuclear Installations), Mr Akira Ono (Chief Decommissioning Officer of Tokyo Electric Power Company
Holdings), Dr Kemal Pasamehmetoglu (Executive Director of the Versatile Test Reactor Project at the
Idaho National Laboratory and Chair of the Nuclear Science Committee), Dr Thierry Schneider (Directorof the Nuclear Protection Evaluation Center [CEPN] and Chair of CRPPH and of Expert Group on Recovery
Management), Mr Tatsuya Shinkawa (Director-General for Nuclear Accident Disaster Response of the
Ministry of Economy, Trade and Industry), Ms Haidy Tadros (Director General, Directorate of Environmental
and Radiation Protection and Assessment of Canadian Nuclear Safety Commission and Chair of theCommittee on Decommissioning of Nuclear Installations and Legacy Management), Mr Petteri Tiippana(Director General of the Radiation and Nuclear Safety Authority of Finland and Chair of CNRA),Dr Hiroyuki Umeki (Executive Director of Nuclear Waste Management Organization of Japan and Chairof the Radioactive Waste Management Committee), Mr William E Webster (Chair of Japan Nuclear Safety
Institute), Prof Hajimu Yamana (President of the Nuclear Damage Compensation and Decommissioning
Facilitation Corporation) and Dr Rosa Yang (EPRI Fellow, Electric Power Research Institute).
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TABLE OF CONTENTS

Table of contents
List of acronyms and abbreviations .........................................................................................................................................

9

Executive summary ............................................................................................................................................................................

11

1. Introduction ........................................................................................................................................................................................

15

2. The accident at the Fukushima Daiichi Nuclear Power Plant .............................................................................

17

2.1.

Basic information about the design and safety characteristics of the Fukushima Daiichi
reactors .........................................................................................................................................................................................

17

2.2.

Synopsis of the accident, the on-site damage, and the local effects .....................................................

18

2.3.

The initial emergency response in Japan ................................................................................................................

21

2.4.

The initial response worldwide .....................................................................................................................................

22

3. Current status of technical and policy responses to the accident at Fukushima Daiichi .................

23

3.1.

Decommissioning the Fukushima Daiichi site: Initial state, strategy and progress .....................

23

3.2.

Remediating surrounding areas: Initial state, plans and progress ..........................................................

28

3.3.

Significant technical and non-technical issues ...................................................................................................

29

3.4.

Restructuring the nuclear legal framework in Japan .......................................................................................

32

4. Safety improvements and other lessons learnt at the international level .................................................

35

4.1.

Key activities and achievements of the Nuclear Energy Agency and member countries .........

35

4.2.

Key activities and achievements of other international organisations ................................................

43

5. Global impact of lessons learnt .............................................................................................................................................

47

5.1.

Lessons learnt on organisational factors and safety culture in NEA member countries ..........

48

5.2.

Accident, emergency and post-accident management: Resilience and balancing decisions .....

50

6. Further challenges stemming from the accident ........................................................................................................

53

6.1.

Technical challenges ............................................................................................................................................................

53

6.2.

Regulation ...................................................................................................................................................................................

55

6.3.

Rebuilding and revitalising communities and local economies ...............................................................

56

6.4.

Public and stakeholder engagement ..........................................................................................................................

57

6.5.

Optimised holistic decision making ...........................................................................................................................

58

6.6.

Institutional systems for ensuring nuclear safety ............................................................................................

59

6.7.

Ethics for leaders and participants .............................................................................................................................

59

6.8.

Intergenerational knowledge and experience ......................................................................................................

60

6.9.

A global system of international organisations working together ..........................................................

60

6.10. Legal preparedness ...............................................................................................................................................................

60

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TABLE OF CONTENTS

8

7. Conclusions and perspectives .................................................................................................................................................

61

Decommissioning and management of radioactive wastes ......................................................................................

62

Nuclear safety and scientific knowledge ...............................................................................................................................

62

Stakeholder involvement and risk communication ........................................................................................................

62

Damage compensation .....................................................................................................................................................................

64

Knowledge management .................................................................................................................................................................

64

8. Recommendations ..........................................................................................................................................................................

65

Recommendation area 1: Regulatory environment .........................................................................................................

66

Recommendation area 2: Systematic approach to safety ...........................................................................................

66

Recommendation area 3: Decommissioning technologies .........................................................................................

66

Recommendation area 4: Waste management and disposal ....................................................................................

66

Recommendation area 5: Damage compensation ...........................................................................................................

66

Recommendation area 6: Stakeholder involvement and risk communication ..............................................

67

Recommendation area 7: Recognition of mental health impacts ..........................................................................

67

Recommendation area 8: Opportunities for economic redevelopment ..............................................................

67

Recommendation area 9: Knowledge management .......................................................................................................

67

References and further reading ...................................................................................................................................................

69

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LIST OF ACRONYMS AND ABBREVIATIONS

List of acronyms and abbreviations
AC

alternating current

ADS

automatic depressurisation systemALARA

as low as reasonably achievable

ALARP

as low as reasonably practicableAM

accident management

ATENA

Atomic Energy Association (Japan)

ATF

accident tolerant fuelBWRboiling water reactor

CNRA

NEA Committee on Nuclear Regulatory Activities

CRPPH

NEA Committee on Radiological Protection and Public Health

CSC

Convention on Supplementary Compensation for Nuclear Damage

CSNI

NEA Committee on the Safety of Nuclear Installations

CSSCF

Country-Specific Safety Culture Forum

CST

condensate storage tank

DAROD

decommissioning and remediation of damaged nuclear facilities

DBA

design basis accidentsDC

direct current

DiD

defence-in-depth

DOE

Department of Energy (US)EOP

emergency operating procedure

ERC

emergency response centre

FDEC

Fukushima Daiichi Decontamination and Decommissioning Engineering Company (TEPCO)

HPCI

high-pressure coolant injection

IAEA

International Atomic Energy Agency

IAM

integrated accident management

ICRP

International Commission on Radiological Protection

ICSA

intensive contamination survey area

INES

International Nuclear Event Scale

IRID

International Research Institute for Nuclear Decommissioning (Japan)

ISF

interim storage facility

ISOE

Information System on Occupational Exposure

JAEA

Japan Atomic Energy Agency

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LIST OF ACRONYMS AND ABBREVIATIONS

10

JANSI

Japan Nuclear Safety Institute

JRC

Joint Research Centre (European Commission)

MAFF

Ministry of Agriculture, Forestry and Fisheries (Japan)

METI

Ministry of Economy, Trade and Industry (Japan)

MEXT

Ministry of Education, Culture, Sports, Science and Technology (Japan)

MoE

Ministry of the Environment (Japan)

MHPSS

mental health and psychosocial support

mSv

millisievert

NDF

Nuclear Damage Compensation and Decommissioning Facilitation Corporation (Japan)

NEA

Nuclear Energy Agency

NLC

NEA Nuclear Law Committee

NRA

Nuclear Regulation Authority (Japan)

NRRC

Nuclear Risk Research Center (Japan)

MSIV

main steam isolation valve

OECD

Organisation for Economic Co-operation and Development

PBq

petabecquerel (equal to 1 015 becquerels)

PCV

primary containment vessel

PSA

probabilistic safety assessment

R&D

research and development

RCIC

reactor core isolation cooling system

RHR

residual heat removal system

RPV

reactor pressure vesselSAsevere accident

SAM

severe accident management

SAMG

severe accident management guidelines

SBO

station blackout

SDA

special decontamination area

SFP

spent fuel pool

SiD

strength-in-depth

SOER

Significant Operating Experience Report

TBq

terabecquerel (equal to 1 012 becquerels)

TEPCO

Tokyo Electric Power Company

TMI

Three Mile Island

TSS

temporary storage sites

UHS

ultimate heat sink

UNSCEAR

United Nations Scientific Committee on the Effects of Atomic Radiation

WANO

World Association of Nuclear Operators

WHO

World Health Organization
FUKUSHIMA DAIICHI NUCLEAR POWER PLANT ACCIDENT, TEN YEARS ON: PROGRESS, LESSONS AND CHALLENGES, NEA No. 7558, © OECD 2021

Executive summaryOn 11 March 2011, Japan was struck by a massive earthquake, which initiated a tsunami thatinundated a large portion of the east coast of Japan. The tsunami caused significant devastationand loss of life. The tsunami also led to a severe accident at the Tokyo Electric Power Company (TEPCO)
Fukushima Daiichi Nuclear Power Plant. Post-accident analyses have verified that the radiation fromthe accident has not led to any direct impact on human health. However, the health and well-beingof more than 150 000 people living in surrounding areas was affected to different degrees (including
some early deaths) as a result of evacuations from the area due to both the tsunami and the nuclear
accident, lack of access to health care or medicines, stress-related problems, and other causes. The
accident also caused disturbance to the daily life of many people and businesses and other activities.
In the immediate aftermath and during the ten years since the accident, Japanese authorities haveundertaken very challenging work to address the on-site and off-site consequences, and rebuild thesocial and economic fabric of the areas impacted by the earthquake and resulting tsunami and thenuclear accident. The global community has come together with Japan to both offer assistance anddraw lessons to further improve nuclear safety worldwide. This endeavour has been greatly facilitatedby the openness of the Japanese government and industry leaders as well as the co-operation ofinternational organisations, governments and companies. The present report, the third in a seriesof major studies on the aftermath of the Fukushima Daiichi accident by the Nuclear Energy Agency(NEA), surveys the research initiatives and the expanding knowledge and action made possible by such
openness and co-operation.
The operating reactors at the Fukushima Daiichi nuclear power plant quickly and effectively shut
down as designed when the earthquake struck on 11 March 2011. However, the tsunami generated
by the earthquake inundated the site approximately 50 minutes later to devastating effect. Primary
and auxiliary reactor cooling circuits and electrical power were lost. Over the course of three days
the cores of Units 1, 2 and 3 (which had been in full operation before the earthquake) overheatedand much of the nuclear fuel in the reactor cores melted. The high temperatures led to chemical
reactions that released significant amounts of hydrogen gas, which exploded and caused structural
damage to Units 1, 3 and 4 (the latter of which on 11 March was in a planned outage). The accident
was categorised at Level 7 of the International Nuclear Event Scale due to high radioactivity releases.
Addressing the considerable challenge of decommissioning the complex nuclear clean-up site,
the Japanese government’s flexible Mid-and-Long-Term Roadmap reflects both the priority for safety
and the implementation system. The 2019 (fifth) revision focusses on managing the contaminatedwater and the treated water stored on site and other radioactive waste, as well as on removal ofboth stored fuel and fuel debris. Environmental remediation is performed to allow wherever possible
the safe return of the population to affected off-site areas; the decontamination in the Special
Decontamination Area had been performed as planned by the end of March 2017, and the work in the
Intensive Contamination Survey Area was completed in March 2018.
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EXECUTIVE SUMMARY

Institutional shortcomings uncovered in the aftermath of the accident prompted the governmentof Japan to completely redesign its approach to nuclear regulation and oversight. It established the
Nuclear Regulation Authority (NRA) and assured its organisational, cultural, financial and politicalindependence. The NRA quickly established new regulatory requirements to assure the safe operationand improved resilience of Japanese facilities in the face of conceivable events. The NRA continues tolearn and is currently adopting a new risk-informed oversight process whose implementation includes
essential discussions and interactions with operators. Japan has also adapted or supplemented
legislation as needed in order to enhance safety, emergency preparedness and the nuclear liability
framework enabling compensation.
At the international level too, much has been learnt. NEA projects supported by participating
member countries and the government of Japan, as well as other NEA joint efforts, have delivered
cross-cutting safety research. A common understanding of the accident has led to improved tools
to support decommissioning and a better quantification and understanding of plant safety margins.
Potential improvements have been identified in several areas such as fuel designs that are moretolerant of accidents and electrical power systems that are more robust. Comprehensive safety reviews
were done across NEA countries to assess readiness for severe accident conditions, and have identified
plant and process improvements to mitigate the potential impact of external hazards. As highlighted
in the 2016 NEA report Five Years after the Fukushima Daiichi Accident: Nuclear Safety Improvements andLessons Learnt, many such measures have been implemented.
To address near-term challenges in handling very low-level post-accident radioactive waste, theNEA examined how to develop a complex waste characterisation and categorisation process. NEA
activities have also focussed on post-accident recovery management, including balancing decisions
in radiological protection, as an important pillar of ensuring public health and well-being. Human
aspects of nuclear safety, such as regulatory safety culture and broader stakeholder involvement indecision making, have been a significant focus of NEA activities. This report details the range of suchinitiatives and the lessons learnt. The activities of other international organisations are acknowledged
and referenced as well.

Cherry blossom trees at the Fukushima Daiichi Nuclear Power Plant. Many cherry trees on thepremises were cut down after the accident for tank installation and ground surface pavement
work (i.e. covering most of the site’s ground by pavement to prevent rainwater from seeping
underground), but some remain for the workers to enjoy. Decontamination is progressing on thepremises, and employees working in the area of the photo do not have to wear protective gear.
Source: TEPCO Holdings

12

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EXECUTIVE SUMMARY

Significant issues remain to be faced as Japan continues the difficult, long-term effort to clean up
the Fukushima Daiichi site and revitalise the surrounding communities impacted by the earthquake
and resulting tsunami and nuclear accident. Technical challenges concern, inter alia: fuel debris
removal; decontamination methods; environmental remediation; and related waste issues. Regulatory
and legal challenges include, inter alia: regulation under uncertainty; reinforcing institutional
nuclear safety systems; legal preparedness; holistic optimisation decisions; and effective regulatory
engagement with a broad range of stakeholders including licensees and the public. The ongoingtask of rebuilding and revitalising communities and local economies should benefit from a guidance
framework outlining a consensual process to facilitate recovery and enable the communities todevelop greater societal resilience. Reflection and action will be needed on preserving intergenerational
knowledge and experience, and also on clarifying ethical values and challenges.
This report finds that significant progress was achieved by Japan in vigorously addressing theaccident through actions and reforms at both the technical and institutional levels. With co-operationfrom the NEA and other international organisations, the technical understanding of the accident
event has progressed significantly, thereby aiding all countries to improve safety and preparedness.
Environmental, social, political and economic aspects, including safety culture, must be a continued
focus if nuclear power is to play its part in addressing the world’s need for clean, safe, reliable energy.
This report concludes by noting that the NEA will continue its strong support for the long processahead to address the aftermath of the Fukushima Daiichi accident and continue developing knowledge
that can be gleaned from the experience the accident has generated. Recommendations are offered innine areas, with advice on how to pursue and enhance:

•
•
•
•
•
•
•
•
•

effective and balanced regulatory transparency, openness and independence;systematic and holistic approaches to safety;
participation in international development of decommissioning technologies;
well-planned waste management and disposal;
improvements to damage compensation practices;
stakeholder involvement and risk communication;
recognition of mental health impacts in protective action and recovery;
opportunities for economic redevelopment; andknowledge management.

These key areas highlight the many opportunities for Japan to provide important and needed
leadership on the international level.

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1. Introduction

On 11 March 2011, Japan was struck by a massive earthquake, which initiated a tsunami thatinundated a large portion of the east coast of Japan. The tsunami caused massive devastation
and approximately 20 000 people were killed or were declared missing. The tsunami also led to one of
the most severe nuclear power site accidents in history, at the Tokyo Electric Power Company (TEPCO)
Fukushima Daiichi Nuclear Power Plant. Three of the station’s six reactors suffered core melts andthe entire facility was severely damaged. The Great East Japan Earthquake, the tsunami, the nuclear
accident, and the resulting release of radioactive material led local authorities to initiate an evacuationof approximately 150 000 people. By deposition, the radioactive releases contaminated a large areaof both the Fukushima Prefecture and others. While post-accident analyses have verified that theradiation from the accident has not led to any direct impact on human health,1 the series of events
impacted the well-being of individuals and the community, and the evacuation is reported to haveresulted in early deaths from the lack of health care or medicines, stress-related problems, etc. (ICRP,
2016).
After nine months, the immediate risks posed by the damaged reactors were brought undercontrol by achieving cold shutdown of the facility. In the years since, Japanese authorities haveundertaken very challenging work to address the on-site and off-site consequences, take forward
the decommissioning of the site, conduct the remediation of the affected areas in the Fukushima
Prefecture and neighbouring prefectures, and rebuild the social and economic fabric of the areas
impacted by the earthquake, the tsunami and the nuclear accident. During and after the accident,
the global community has come together with Japan to both offer any needed assistance and draw
lessons to further improve nuclear safety worldwide. This endeavour has been greatly facilitated by the
openness of the Japanese government and industry leaders as well as the co-operation of internationalorganisations, governments and companies.
This is the third major report by the Nuclear Energy Agency (NEA) on the Fukushima Daiichi
accident. In 2013, the NEA published its first report, The Fukushima Daiichi Nuclear Power Plant Accident(NEA, 2013d). This document focused on the NEA’s and its member states’ immediate response to
the accident. The second major NEA report, Five Years after the Fukushima Daiichi Nuclear Power Plant
Accident (NEA, 2016b), discussed the measures taken or in progress in NEA member states to improve
1.
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) assessed radiation exposures ofthe public, workers and non-human biota that resulted from the accident at the Fukushima Daiichi Nuclear Power Plant. Findings,
including discussion of health implications, were presented to the General Assembly of the United Nations in 2013 (UNSCEAR,
2014; (www.unscear.org/unscear/en/fukushima.html, accessed 22 October 2020). UNSCEAR has gone on to discuss moredetailed analyses and new information that subsequently became available (UNSCEAR, 2015; 2016; 2017); a revised report isin preparation (UNSCEAR, forthcoming).

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INTRODUCTION

further the safety of nuclear facilities in line with the underlying principle of “continuous learningand improvement.” All high-risk industries, including nuclear, strive to learn and improve from all
experience. The accident at Fukushima Daiichi has highlighted the need to ensure the lessons learnt
are broadly shared and addressed now and in the future.
This report is intended to assist Japan’s recovery from the accident for a better future for all,and more generally enhance the safe use of nuclear energy worldwide. It summarises, in a ten-year
retrospective: the circumstances of the accident, the initial response in Japan and worldwide, and thesocietal impact (Chapter 2); the current status of the Fukushima Daiichi site, including the progress
on its decommissioning and the environmental remediation of the surrounding areas, the technicalissues associated with these combined activities, and the wider social and political aspects (Chapter 3);
the activities of the NEA, other international organisations and NEA member countries (Chapter 4); theglobal impact and lessons learnt (Chapter 5). Looking forward, Chapter 6 addresses further challenges
and, finally, Chapters 7 and 8 identify conclusions and make policy recommendations.
This report, as did the other major reports, seeks to complement the work of other internationaland national organisations including the International Atomic Energy Agency (IAEA) and the World
Association of Nuclear Operators (WANO) which have also contributed greatly to further understanding
and safety improvements stemming from the accident at Fukushima Daiichi. This report has been
written using available information and the insights gained from interviews conducted with a broadgroup of experts and nuclear leaders in Japan and from around the world.
While the report may be of interest to a wide range of individuals and organisations, including thegeneral public, it is intended to be useful in particular to policy makers and leaders involved in assuring
a healthy and safe society through the peaceful use of nuclear energy. Even more fundamentally, thisreport may assist those leading the rebuilding of society and communities after major catastrophic
events, such as the Fukushima Daiichi nuclear accident, and in developing effective recovery plans.

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2. The accident at the Fukushima Daiichi
Nuclear Power Plant
2.1.

Basic information about the design and safety characteristicsof the Fukushima Daiichi reactors

Understanding the accident and the responses to it does not require a deep technical knowledge of
nuclear technology, but rather an understanding of the basic design of the Fukushima Daiichi reactors
and of how to keep such technology safe.

Figure 1.1: Basic design of Fukushima Daiichi boiling water reactors

Well shield plug

Operating floor

Spent
fuel
pool

4th floor

Primary containment
vessel (PCV)

Reactor pressure
vessel (RPV)

3rd floor

2nd floor

1st floor

1stbasement
floor

Component
pit

Pedestal
Vent tube

Suppression
chamber (S/C)
Torus room

Source: NDF.

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THE ACCIDENT AT THE FUKUSHIMA DAIICHI NUCLEAR POWER PLANT

Figure 1.1 outlines the characteristics of the boiling water reactors (BWRs) on this site. They have
five main elements relevant to this discussion:• the reactor core, which includes nuclear fuel assemblies clad in zirconium alloy, as well as
control rods;• the reactor pressure vessel (RPV), which encloses the reactor core and water/steam used totransfer the heat;• the primary containment vessel (PCV), consisting of: a robust free-standing bulb-shaped steel

drywell backed by a reinforced concrete shell, which acts as a further containment, and thewetwell;• the suppression chamber (SC), a torus-shaped steel tank holding water inside to absorb steam
and thus reduce or “suppress” pressure;• the spent fuel pool (SFP), where fuel removed from inside the reactor is held for cooling over a
period of years, while it emits high levels of heat and radiation.

These elements support the three essential safety functions:• to control the nuclear reactions in the reactor core as well as harmful chemical reactions that
may occur in materials at high temperatures;• to cool the reactor fuel;• to contain the radiation and radioactive material.
These safety functions are interrelated: if the fuel is not cooled to remove decay heat,1 it can begin
to melt, leading to chemical reactions that can result in overpressurisation of the PCV and breach of
the containment barrier.
To ensure that these three functions are maintained, the design and engineering of BWRs includes
several safety systems that rely on the following principles: defence in depth; diversity; redundancy;
physical separation and functional independence; and so forth. The safety systems in BWRs normallyrequire electricity or other energy sources to operate effectively.2
In simple terms, at Fukushima Daiichi a loss of electrical power caused the cooling systems to stopfunctioning, which caused the fuel assemblies to overheat and melt, in turn causing the zirconium
fuel cladding to react with high temperature steam, releasing hydrogen and overpressurising the PCV.
The released hydrogen ignited, causing large explosions that damaged the reactor buildings.
The complex sequence of events that led to this nuclear accident is explained below.

2.2.

Synopsis of the accident, the on-site damage, and the local effects

The Japan Meteorological Agency reported that on 11 March 2011 at 2:46 p.m. (Japan Standard Time), theGreat East Japan Earthquake3 (often dubbed “Tohoku Earthquake”) occurred and shook the eastern partof Japan with a highest point intensity of 7 (the maximum point of the Japanese intensity scale). The
earthquake, of 9.0 magnitude on the Richter scale, was centred about 130 km east of Oshika Peninsula,
Miyagi Prefecture, Japan, at a hypocentre depth of 24 km. The seismic source area of the earthquake
was in the plate boundary between the North American tectonic plate and the Pacific tectonic plate.
The displacement in the seabed caused by the seismic event generated a chain of tsunamis whichinundated hundreds of square kilometres of the Japanese coastline, destroyed or damaged over a
million buildings in coastal ports and towns, and resulted in the death of approximately 19 729 people,
with a further 2 559 people missing and 6 233 injured.4
1.
The heat produced by the decay of radioactive fission products after a reactor has been shut down.
2.
In many newer nuclear plant designs, often referred to as “Generation III or IV” technologies, plant safety relies less onelectricity and, instead, applies natural forces such as gravity and convection to prevent a nuclear accident. Some Generation III
reactors rely on electricity with increased diversity and redundancy, while others rely on passive features.
3.
Website of the Japan Meteorological Agency, www.jma.go.jp/jma/en/2011_Earthquake/2011_Earthquake.html (accessed
22 October 2020).
4.
Website of the Reconstruction Agency of the Government of Japan (accessed 22 October 2020), www.reconstruction.go.jp/
english/topics/GEJE/index.html.

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THE ACCIDENT AT THE FUKUSHIMA DAIICHI NUCLEAR POWER PLANT

The Fukushima Daiichi Nuclear Power Plant, owned and operated by TEPCO, has six BWRs andis located just on the border of the towns of Okuma and Futaba, in the Fukushima Prefecture ofnortheast Japan. The earthquake caused no damage to the reactor safety systems, and the threeoperating units (Units 1, 2 and 3) responded as designed and automatically shut down upon indicationof high vibratory ground motion. Unit 4 was in a planned outage, and all nuclear fuel assemblies had
been placed in the SFP for a scheduled inspection; Units 5 and 6 were both under preparation forrestart after periodic fuel change. However, earthquake damage caused the loss of all external power
supply sources, i.e. six separate sets of electricity transmission lines; as designed, the emergency
diesel generators started to provide electrical power to emergency equipment.
At this stage of the event, cooling for the Unit 1 reactor was initially maintained through theundamaged automatic functioning of two isolation condensers5 returning condensed water to the
RPV. However, due to overcooling of the reactor cooling system, operators in the main control room
reverted to cycling only one of the isolation condensers. Cooling for the Unit 2 and 3 reactors was
initially maintained automatically using the reactor core isolation cooling (RCIC) system in Unit 2 andboth RCIC and the high-pressure coolant injection (HPCI) systems in Unit 3. At this point, the reactors
were in a safe condition and the cores were cooling as designed.
Approximately 50 minutes after the earthquake, the tsunami that struck a large portion of northeastern Japan inundated the Fukushima Daiichi site, bringing a huge wave of water and debris crashinginto the facility, particularly Units 1, 2, 3 and 4 and their supporting systems. The tsunami submerged
and damaged the seawater pumps for both the main condenser circuits and the auxiliary cooling
circuits, notably the residual heat removal (RHR) cooling system. The emergency diesel generators,
the electrical switchgear and the direct current6 (DC) batteries, almost all of which were located in thebasements of the turbine buildings, were inundated. Note that two diesel generators for Units 2 and 4
and DC batteries at Unit 3 survived the tsunami, before the diesel generators became inoperable due
to a switchgear failure and the depletion of DC batteries. An air-cooled emergency generator dedicatedto Unit 6 had been installed on higher ground and survived the tsunami.
These events led to a complete loss of electrical power (a scenario known in the nuclear sector as
a “station blackout”) at Units 1, 2 and 3 which had all been in full operation before the earthquake.
While Unit 4 was not in operation and no fuel was in the reactor, the loss of power left the operators
without instrumentation, controls, or lighting and unable to monitor the condition of the used fuel inthe reactor’s SFP nor deliver any needed cooling to the pool.
Conditions at the site were very difficult. As described above, the loss of electrical power anddisabling of multiple systems prevented operators from cooling the reactors and the SFPs. Further,
the earthquake and tsunamis damaged and obstructed roads, which made it difficult for off-site
emergency services to gain access to the site.
Without cooling water, the cores of Units 1, 2 and 3 overheated and much of the fuel melted overthe first three days. Many official reports document and catalogue the core damage, which include
zirconium structures in the core reacting with high temperature water/steam and releasing hydrogenthrough the resulting chemical reaction. The highly flammable hydrogen gas generated by this hightemperature process caused explosions on 12 March at Unit 1, 14 March at Unit 3, and 15 March at
Unit 4. In Units 1 and 3, these explosions significantly damaged the reactor buildings, destroying theupper structures of the buildings.
At Unit 1, the return valves of the isolation condenser closed after the loss of power, meaningthat the ability to manipulate the cooling function of the isolation condenser was lost. This occurred
unknown to the Unit 1 shift supervisor. Reactor decay heat accumulated in the suppression chamberwith no capability to remove heat via the RHR to the ultimate heat sink of the ocean. Core melting
5.
The isolation condenser in a boiling water reactor is a safety system that removes decay heat when for any reason theconnection between the reactor and the main condenser is disrupted, i.e. the reactor is isolated. The isolation condenser has asmaller heat sink capacity than the main condenser.
6.
In DC systems, electric current moves in one direction with constant strength. DC is obtained from storage sources such asbatteries.
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THE ACCIDENT AT THE FUKUSHIMA DAIICHI NUCLEAR POWER PLANT

began about 5 hours later, which led to pressurisation of the PCV from the accumulation of hydrogengas and steam within the PCV. This high containment pressure is estimated to have produced a leakat the containment upper head, which released fission products and hydrogen gas into the upper
operating floor of the reactor building, resulting after about 24 hours in the hydrogen explosion at theUnit 1 reactor building.
At Unit 2, the RCIC system continued to operate for nearly three days, providing makeup water
to the reactor from the outside-of-containment condensate storage tank (CST) and later from thein-containment suppression chamber water. Eventually the Unit 2 RCIC failed and pressure in the RPV
increased until the operators opened a safety relief valve to release the pressure in an attempt to allow
water to be injected using fire trucks. The action was ultimately unsuccessful and the Unit 2 reactor
core melted as well. However, the three days of cooling using the RCIC and the attempt to inject water
may have reduced the severity of the meltdown, given that much of the Unit 2 fuel material was
retained in the lower head of the vessel (according to post-accident RPV imaging). In addition, theUnit 2 reactor building did not suffer a hydrogen explosion. This was likely due to the dislodgementof the Unit 2 blowout panel caused by the Unit 1 reactor building explosion; with this building panel
removed, hydrogen gas was able to escape the Unit 2 building before a flammable mixture could form.
The second reactor to suffer fuel melting was Unit 3, where the RCIC system was started following
closure of the main steam isolation valves (MSIVs). In Unit 3, some battery power remained available
for more than 24 hours and the RCIC system was initially used to move heat from the reactor to the
suppression chamber. However, as in Unit 1 there was no RHR available to move suppression chamberheat to the ultimate heat sink of the ocean, and temperatures and pressures in the suppression
chamber and PCV increased continuously. The RCIC system stopped on 12 March and the HPCI
system automatically started. The HPCI system was unable to inject water under the degrading RPV
conditions and operators shut down the HPCI system to alter the injection route. However, operators
were not successful in establishing the alternative injection line or reactivating the RCIC system.
RPV pressure returned to the SRV cycling pressure until an unintended activation of the automatic
depressurisation system (ADS) occurred. Before that, core damage and hydrogen generation occurred,
resulting in an accumulation of hydrogen and subsequent explosion in the reactor building upper
floor area, destroying the upper reactor building. Structural debris from the reactor buildings of both
Units 1 and 3 fell into their respective SFPs.
As noted above, Unit 4 was undergoing a scheduled outage; it had been shut down prior to theaccident and the reactor fuel had been placed in the SFP. However, Unit 4 experienced a hydrogen gas
explosion on 15 March that was subsequently determined to be caused by gas backflow from Unit 3 toUnit 4 via the common stack and the standby gas treatment system (SGTS) pipes. At the time, however,
because operators lacked the ability to monitor SFP water level and temperature, they thought the
explosion might have been caused by overheated, uncovered fuel in the SFPs of Units 3 and/or 4.
This concern prompted several mitigation efforts, including remote visual inspection via helicopter
which confirmed the presence of sufficient water in the Unit 4 SFP, but was inconclusive regarding thelevel in the Unit 3 SFP. As a result, initial airdrops of water from helicopters, and intermittent water
spray from fire engines and concrete pump trucks, were used until the end of March. Further analyses
conducted by TEPCO confirmed later that an adequate water level was maintained in each of the SFPs
of Units 1 to 4 throughout the aftermath of the accident, and that the concentrations of radioactive
materials in the pool water indicated that the fuel in the pools had been kept in sound condition.
TEPCO also restored circulating cooling and purification systems of the pool water in late 2011.
The complete loss of electrical power to the damaged units extinguished all control room lighting
and instrumentation, and severely limited the ability of operators to communicate with others outside
the control room. Units 1, 2, 3 and 4 remained without alternating current (AC)7 electrical power
for between nine and fourteen days respectively after the station blackout. Stable cooling (or cold
shutdown) of all the reactors and SFPs was not fully confirmed until December 2011. This delay inrestoration of safety functions required plant operators to carry out mitigative actions in the power
7.
AC current is that used for the transmission of electricity on grids which is generated by various types of power systems,
including diesel generators.

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THE ACCIDENT AT THE FUKUSHIMA DAIICHI NUCLEAR POWER PLANT

station amidst challenging and hazardous conditions, including debris from the tsunami, darkness,high temperatures, high radiation, and repeated aftershocks and tsunami warnings. Operators worked
heroically for many days under great stress and fatigue to restore safety functions and attempt tomitigate the damage to the plant.
The Nuclear and Industrial Safety Agency of the Ministry of Economy, Trade and Industry (METI)
categorised the accident at Fukushima Daiichi as a Level 7 event on the International Atomic Energy
Agency’s (IAEA) International Nuclear Event Scale. This highest point on the IAEA scale was assigned
due to high radioactivity releases, eventually totalling as follows: approximately 100-500 PBq (I-131)
and 6-20 PBq (Cs137) as atmospheric releases (80% of which was deposited over the ocean); 10-20 PBq(I-131) and 3-6 PBq (Cs137) released directly
to the ocean (UNSCEAR, 2014); 60 TBq toground water; and an additional 0.5 TBq/y
to plant harbour water stemming from theimplementation of measures to prevent
groundwater entering into the ocean. In view ofthese releases, the Fukushima Daiichi accident
is considered the worst civil nuclear accident
since the severe accident at Chernobyl in 1986.
While post-accident analyses have verified
that the radiation from the accident has not
led to any direct impact on human health,the evacuation of more than 150 000 people
living in surrounding areas is reported tohave resulted in early deaths associated withthe evacuation of citizens from the area, lackof access to health care or medicines, stressrelated problems, and other causes. The seriesof events – the earthquake, the resulting
tsunami and nuclear accident, and later theevacuation and some other post-accident
recovery measures – impacted the well-beingof individuals and the community.

2.3.

Workers maintaining a tank storing treated water on thepremises of the Fukushima Daiichi Nuclear Power Plant. Source:
TEPCO Holdings

The initial emergency response in Japan

Approximately 15 minutes after the Great East Japan Earthquake, the Emergency Response Centre(ERC) headed by the Site Superintendent at Fukushima Daiichi was activated. The ERC was located ina seismically isolated building, outfitted with an autonomous electrical power supply and ventilation
systems with filtration devices. The use of this building enabled mitigatory actions to continue at thesite during the response to the accident. Although arrangements existed prior to the accident for theon-site ERC to request support (e.g. additional staff and equipment) from TEPCO Headquarters, theextensive damage to the transportation infrastructure from the earthquake and tsunami, as well as
insufficient pre-planning, hindered the timely delivery and deployment of such support at Fukushima
Daiichi.
In response to the emergency, personnel from TEPCO, contractors, and staff from other Japanese
nuclear power plants (not operated by TEPCO) were dispatched to the site to assist with various
tasks, including restoring power and monitoring instruments, injecting cooling water into reactors,
removing rubble and monitoring radiation levels. Personnel from national government agencies andorganisations – such as the Japan Self-Defence Force, police and firefighters – were also dispatched tothe site to assist in mitigation and recovery activities, including operating the large equipment needed
to spray water onto the spent fuel and to move debris.
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THE ACCIDENT AT THE FUKUSHIMA DAIICHI NUCLEAR POWER PLANT

Among the many actions to protect the public living near Fukushima Daiichi, the national
government declared a nuclear emergency and an evacuation order was issued on 11 March for people
within a 3 km radius of the site. As the situation at the site worsened, the decision was made on
12 March to extend the evacuation zone to 20 km.
From the beginning, Japan worked closely with other countries and international organisations,sharing information and reports. Many countries8 offered assistance including the United States whose
Armed Forces stationed in and around Japan provided humanitarian assistance and disaster relief aswell as direct support to Fukushima Daiichi Nuclear Power Plant in Operation “Tomodachi (Friends).”

2.4.

The initial response worldwide

All NEA member countries took early actions to ensure, improve and confirm the safety of their
existing and planned nuclear power plants and the protection of people from the hazards of exposure
to radiation (NEA, 2013; ENSREG, 2013; IAEA, 2014b). Preliminary safety reviews represented anessential part of these actions. The reviews concluded that there was no technical basis for requiring
the currently operating plants to shut down. The reviews also found that short-term actions taken byplant operators (where necessary) provided assurance of the continued safe operation of the plants,
while more thorough evaluations of the accident and of the impact on continued safe operation were
performed.
The accident also highlighted a number of other issues, including the importance of a strong
nuclear safety culture; the challenges to supporting reliable human performance under extreme
conditions; communications and stakeholder involvement in decision making; and management of
the impact of post-accident contamination on food and goods (NEA, 2016b).
One important and beneficial outcome of the global response was the development of muchgreater international discussion and co-operation to enhance nuclear safety, particularly throughinstitutions such as the NEA, IAEA and the World Association of Nuclear Operators. There exists today
more international co-ordination in the nuclear safety area than at any previous time.

8.
The government and TEPCO received goods and supplies (pumps, fire engines, remote controlled robots, dosimeters, personal
protection equipment, germanium semiconductor detectors and other tools) from many countries and international organisations.

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3. Current status of technical and policy
responses to the accident at Fukushima Daiichi
3.1.

Decommissioning the Fukushima Daiichi site: Initial state, strategy andprogress

Decommissioning may be defined in the nuclear sector as “achieving the goal of carrying out alladministrative, technical and societal actions to allow the removal of a nuclear site from regulatory
control.”1 The process may target different end state degrees of the former nuclear site’s availability forother activities, ranging from “brown field” to “green field” status. Decommissioning, which includes
many component activities ranging from reactor shutdown to site decontamination, is a complex
multi-year process in the best of cases.
Decommissioning of the Fukushima Daiichi site is a unique challenge given the initial state of thesite after the accident and limited experience in Japan with the decommissioning of complex nuclear
clean-up sites. In addition, decommissioning activities are inherently different from operating a
nuclear power plant and, therefore, constitute a challenge for both the site operator and the regulator.
Further, the clean-up activities began as Japan and its people were still recovering from the largest
earthquake and tsunami that Japan had suffered in recorded history. Plans and analyses undertaken
since the accident indicate that decommissioning of the site will take several decades and the end
state has not been determined. When considering the decommissioning progress to date this context
has to be taken into account.

3.1.1.

Initial state of the site after the accident

The initial state of the Fukushima Daiichi Nuclear Power Plant immediately after the earthquake
and tsunami was one of devastation. Inundation of the site by the tsunami blocked roads and accessroutes, and caused extensive damage to the buildings. In this early stage, only Units 5 and 6 retainedalternating current (AC) power. The diesel generators for Units 1-4 had failed and no off-site powersources were yet available.
The devastation was subsequently increased by the hydrogen explosions in Units 1, 3 and 4.
Moreover, the fuel in three reactors (1, 2 and 3) had melted and some of the resulting corium material
had migrated from the reactor pressure vessels into the containment vessels. Importantly, there werehigh radiation levels around the site both from direct radiation shine and from airborne radioactive
contamination. This hampered recovery operations, limiting the amount of time workers could spend
close to high radiation sources, and work in all areas required the use of protective clothing andrespiratory protection.
1.

NEA (2020), Decommissioning and legacy management, www.oecd-nea.org/decommissioning (accessed 22 October 2020).

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CURRENT STATUS OF TECHNICAL AND POLICY RESPONSES TO THE ACCIDENT AT FUKUSHIMA DAIICHIThe first priority during an initial recovery stage was to stabilise the site to reduce potential risks
to the site personnel and the surrounding communities. Only when the site was made sufficiently
safe could consideration be given to decommissioning. This stabilisation included the following:
restoring electrical power to the site from off-site sources; arranging robust cooling of the reactor
cores and spent fuel pools (SFPs); establishing criticality monitoring and protection; clearing accessroutes; reinforcing structures where necessary to ensure they were safe; installing air filtration units
in buildings; stabilising contamination on surfaces to reduce re-suspension of radioactive particles.
A particular problem for site personnel during the initial phase of the accident was the increasing
volume of highly contaminated water accumulating on site and overflowing to the sea.
The operators faced a daunting task to stabilise the reactors to reach what was deemed to bea “cold shutdown condition”2 where the reactor pressure vessel (RPV) temperature at the bottom
generally was below 100℃ and the public radiation exposure from any additional release wassignificantly minimised.3 This condition, which was achieved in December 2011, was an importantmilestone. Decommissioning was begun in earnest at this point.

3.1.2.

Decommissioning responsibilities and strategy

To respond to the complexities and uncertainties associated with decommissioning the multiple
damaged reactors at Fukushima Daiichi, the decommissioning organisational structure has added
aspects to those found in nominal circumstances. Five main elements have been involved:• the national government, predominately the Ministry of the Economy, Trade and Industry (METI)
and the Ministry of Education, Culture, Sports, Science and Technology (MEXT) – establishingnecessary policies and legislation, authorising funding, and setting major milestones;• the independent regulator for the site (the Japanese Nuclear Regulation Authority, NRA) – setting
rules for decommissioning and regulating the activities on the site;• the Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF)– establishing the technical strategy for decommissioning, overseeing and managing thedecommissioning programme in line with the strategy, deciding the amount of funds that theTokyo Electric Power Company (TEPCO) should hold in reserve with NDF in each fiscal year andjointly establishing the plan for fund withdrawal to meet decommissioning needs;• the responsible operator/decommissioning company, TEPCO – developing the Mid-and-LongTerm Decommissioning Action Plan in line with the Roadmap set by the government and the
NDF Strategy and undertaking the decommissioning on the site;• the Japan Atomic Energy Agency (JAEA) – implementing research and development (R&D)
programmes and human resource development programmes in accordance with the technicalstrategy for decommissioning established by the NDF.
Decommissioning of a complex radiological contaminated site such as Fukushima Daiichi implies
a considerable number of unknowns, some of which will arise or be resolved only with time. Thus,
decommissioning must be conducted using a cautious, stepwise approach without the benefit ofan established detailed safety case covering the entire process. A flexible plan, reflecting both thepriority for safety and co-ordinated resource allocations, was first established in December 2011 as
the Japanese government’s Mid-and-Long-Term Roadmap (METI, 2011)4, and it was revised five times.
The latest revision (METI, 2019) lays out the following technical aspects for action: i) the contaminatedwater management; ii) removal of fuel from SFPs; iii) retrieval of fuel debris; and iv) the management of
2.
This is different from the normal definition of cold shutdown when after normal shutdown and cooling the reactor pressure
vessel is at atmospheric pressure and the water temperature is sufficiently below boiling point to allow the reactor pressure
vessel to be opened up e.g. for refueling. Several of the Fukushima Daiichi reactor pressure vessels had been breached andhence would not hold water as would be normal for cold shutdown conditions.
3.
After this effort, the exposure of the public by additional release is being significantly held down as well, and a target of not
greater than 1 mSv/year at the site boundary was achieved in March 2016.
4.
The Mid-and-Long-Term Roadmap is set and revised by “the Inter-Ministerial Council for Contaminated Water andDecommissioning Issues” for which METI provides the secretariat.

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CURRENT STATUS OF TECHNICAL AND POLICY RESPONSES TO THE ACCIDENT AT FUKUSHIMA DAIICHI

radioactive wastes. Human resource development, technical research and development, international
co-operation programmes and symbiosis with local communities are covered as well.
The initial strategy for decommissioning in 2011 had to take into account the following
considerations:• Damage to fuel in the reactor building SFPs of Units 1, 3 and 4 potentially may have been caused
by debris.

• Containment of the buildings was breached. In the case of Units 1 and 3 there was extensive

damage to the top of the reactor building (on the fifth floor and above), such that the SFPs
were substantially open to the environment. For the case of the reactor building of Unit 4, theexplosion damaged and compromised the structural robustness of the third and fourth floors.

• Heavily contaminated water had accumulated in some of the buildings, particularly the turbine

and reactor buildings, and underground conduits connected to the buildings. The water thatwas being used to continuously cool reactors Units 1, 2 and 3 was escaping and mixing withground water and rain water entering the buildings.

Fuel debris was and is very highly radioactive, of unknown form and properties, and with apotential (albeit remote) risk of re-criticality. After extensive investigations, using robotic cameras
inside the primary containment vessels (PCVs), accident progression analysis and muon radiography,
a general understanding of the location of the fuel debris is now established.
The initial strategy has been reviewed periodically and refined by the incorporation of further
knowledge and technical understanding. The NDF has established five guiding principles5 for thedecommissioning giving substance to the priority for safety or reducing risk. It has also developed
a risk reduction and safety assurance strategy for decommissioning, and an extensive technicalprogramme. The NDF’s activities and work programmes, as well as these principles, are specified in its
strategic plan (NDF, 2020).

3.1.3.

Progress in decommissioning

In co-operation with TEPCO, METI updates information
monthly in regard to the progress of decommissioning,
including the situation of fuel removal from the four units,
on-site storage and retrieval of fuel debris (METI, 2020b).
Many enablers to successful safe decommissioning havebeen put into place, including:• maintaining the safety of the reactors;• reducing the dose levels on site;• optimising workers’ use of personal protective

equipment to enable on-site work to progress more
efficiently and with better attention to industrial
hazards;• providing welfare and other structures such as
canteens and rest centres;• creating company structures such as TEPCO’s Fukushima

Daiichi Decontamination and Decommissioning
Engineering Company (FDEC);• introducing project management processes reflecting
the project nature of the decommissioning programme;• research and development;• local community engagement;• international co-operation.
5.

Workers dismantling the upper part ofthe exhaust stack of Units 1 and 2 of the
Fukushima Daiichi Nuclear Power Plant.
This operation was completed in May 2020.
Source: TEPCO Holdings

Namely: safe, proven, efficient, timely and field-oriented (NDF, 2020).

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Alongside the specific decommissioning activities described below, other activities to improvesafety have included using remote heavy equipment to secure the removal of the upper portions of
the reactor 1 and 2 exhaust stack which was contaminated and partially damaged. This work wascompleted by a local business, illustrating the operator’s strong intention to co-operate with local
enterprise as much as possible.

Fuel removal from reactor building SFPs
Fuel removal is a process to transfer fuel assemblies in the SFPs of reactor buildings of the Units 1 to 4
to more stable storage in the site. Before starting the transfer, the units need complete preparatory
works, such as removal of rubble and debris in the SFPs especially in Units 1 and 3, reduction ofdose levels of the operation floors, installation of weather shielding, and installing the fuel handlingmachines and cranes that must handle the required casks containing the fuel which, loaded, weighsome 50 to 100 metric tonnes.

Recovered fuel storage
There are two centralised spent fuel storage facilities on the site: a common pool, where the fuel isstored under water to provide shielding and cooling; and an interim cask storage area, where the spent
fuel is stored dry in storage casks. This latter area has a much smaller capacity compared to the common
pool. The interim cask storage area receives spent fuel from the common pool, thereby releasing space
for the fuel recovered from the reactor SFPs. At the time of the accident, there were nine existing drycasks of fuel stored on site. The area of cask storage is planned to be expanded in the future.
Initially, the common pool had to be restored to a condition sufficient for it to handle fuel. This wasachieved in November 2012. The operation of the interim dry cask storage area started in April 2013
with the receipt of the nine existing dry casks. In the middle of 2013, spent fuel started to be removed
from the common pool for storage in dry casks. Later that year the interim area commenced storing
spent fuel from Unit 4.

Fuel debris retrieval
Retrieval of fuel debris relies on an understanding of
its actual distribution in reactors 1 to 3. The current
understanding remains uncertain and efforts are ongoing
to try to refine it. It has been built up from measurements
during the accident, muon radiography, analyticalmodelling and understanding of the progression of theaccident from tests and in-situ surveys using robotic
equipment. The surveys have been hampered by the highradiation dose rates in the access routes to the ports in the
PCVs and by the very high dose rates in the PCVs. Directsurveys inside the RPVs are still not possible. R&D projects
are underway to establish access routes and investigation
technologies inside the RPVs.
NDF has undertaken considerable work on the technicalbasis for fuel debris retrieval, as shown by its TechnicalStrategic Plan (NDF, 2020). Its 2019 Technical Strategic
Plan was used as a basis for TEPCO’s Mid-and-Long-Term
Decommissioning Action Plan issued in March 2020. Thisis the foundation for the next TEPCO Mid-and-Long-Term
Decommissioning Action Plan detailing the work to fulfil
the Roadmap.
Unit 2 has been chosen as the first unit to start fueldebris retrieval. It is intended to be conducted in a stepwise
approach commencing by the experimental retrieval of

26

Common pool at the Fukushima Daiichi Nuclear
Power Plant for storage of spent and fresh
fuel rod assemblies. The transfer of fuel rod
assemblies from reactor building pools to thecommon pool was completed in February 2021
for Unit 3, and in December 2014 for Unit 4.
Source: TEPCO Holdings

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CURRENT STATUS OF TECHNICAL AND POLICY RESPONSES TO THE ACCIDENT AT FUKUSHIMA DAIICHI

debris using a long-reach (approximately 22 metre) robotic
arm6 going through a sealed opening in the side of the PCV
to obtain gram quantities for analysis. This first step wasplanned to start in 2021 in line with the current Roadmap.
In December 2020, however, TEPCO and the International
Research Institute for Nuclear Decommissioning (IRID)
announced that the start would be postponed due to thedelay in the development of equipment, due mainly to theimpact of the COVID-19 pandemic. The first step will befollowed by a gradual increase of the scale of retrieval. Further
safety and process analysis will be conducted throughout
operations to help refine the approach and maximise safety.
Considerations include maintaining adequate cooling,
criticality monitoring and control, containment (especiallyof any dusts generated), and providing adequate shielding.
Further work is in hand to determine the requirements
and provide the appropriate facilities for handling,
analysing and storing the fuel debris retrieved.

Robot arm part of the system to be used forthe trial retrieval of fuel debris inside theUnit 2 primary containment vessel at the
Fukushima Daiichi Nuclear Power Plant. It wasdeveloped in the United Kingdom and after
being shipped to Japan, it will be used once
its performance is confirmed and operators aretrained with the help of a simulator. Source:International Research Institute for Nuclear
Decommissioning (IRID)

Contaminated water management
A large quantity of contaminated water was created during the accident and additional water became
contaminated and accumulated as it contacted radioactive material or reactor fuel debris. The
contaminated water is from three main sources, arising from: the continuing cooling of the reactors;
ground water flowing into the buildings; and rain falling onto and into buildings. Currently, measures
ensure that the level of water, some heavily contaminated, in the basement of the buildings remains
below the level of surrounding groundwater.
Measures to manage the accumulation of contaminated water have been based on three policies:• remove the source of the water contamination;• redirect and hence reduce the amount of clean water interacting with contamination sources;• retain contaminated water and prevent it from leaking out to the environment.
A substantial number of measures in line with these policies have been put in place, including
groundwater bypass, subdrains, and the installation of impermeable walls under the ground.
The engineering measures associated with this effort have been impressive and progress has
been continual. The amount of contaminated water generated has decreased from an average ofapproximately 470 m³/day during the twelve months until March 2015 when the measures went into
operation, to an average of approximately 180 m³/day during the twelve months until March 2020
(METI, 2020b). In addition, facilities using existing technologies for treating the contaminated water
were put in place early on. These are of two main types:• KURION and SARRY, mainly for removing caesium and strontium from the water accumulated
in building basements;• ALPS, a multi-nuclide removal system.
Secondary waste generated by the water treatment facilities is stored in robust containers while theprocessed water is accumulated in large tanks. Originally, many tanks were of a bolted panel design
and were deemed more vulnerable to leakage, especially from potential future seismic events that
could challenge the integrity of the tanks, and required maintenance. All of these tanks for storing thetreated water have been replaced with smooth welded panel tanks. This tank replacement achieved
a reduction in risk associated with leakage and reduced the regular maintenance and inspection
requirements that placed additional demands on the workforce.
6.

A suitable robotic arm is being procured from a company in the United Kingdom experienced in the production of such equipment.

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These processes have been very effective in removing nearly all the radioactivity from thecontaminated water, with the exception of tritium7 and carbon-14. For the case of treated water with ahigh concentration of radioactivity, TEPCO will process the water to reduce further the concentration.8
The difficulties in resolving the issue of treated water with residual tritium illustrate the need for
effective risk communication and stakeholder engagement.

Solid waste management
Radioactive solid waste has been and will be accumulated on the site in many forms and with levelsof radioactivity ranging from slightly contaminated trees and rubble to very highly radioactive
material from inside the reactors. This waste needs to be characterised, and suitable treatment andconditioning options and storage have to be determined. Appropriate facilities must be put in placeand operated. Additionally, long-term storage or disposal arrangements must be established.
Basic policies for solid waste management on the site were established in the 2017 NDF TechnicalStrategic Plan and summarised in that year’s revision of the Roadmap. Further technical and R&D work
has been defined and will be implemented in accordance with the NDF Technical Strategic Plan (NDF,
2020).
Some facilities related to waste management facilities have been brought into operation on thesite, including: interim tentative storage areas of solid waste; an incinerator for combustible waste; asolid waste storehouse; and analytical laboratories.

3.2.

Remediating surrounding areas: Initial state, plans and progress

3.2.1.

Initial state of the surrounding areas after the accident

The Fukushima Daiichi accident caused off-site releases that led to the evacuation of people froma 20 km radius around the site and some high dose areas, as well as to sheltering over a wider area
up to 30 km within which voluntary evacuation was recommended by the Japanese government.
Additionally, radioactive particles fell into the surrounding ocean and large quantities of radioactive
water migrated from the site directly into the ocean. Restrictions were placed on food and water
consumption and distribution. Initial dose rates in the evacuation zones were high: from 50 to
100 mSv/year, estimated from measurements in November 2011, in Iitate Village, 35 km north-west
from the site; closer to the site, annual dose rate estimates increased by over 100 mSv/year (IAEA,
2013).9 Aerial survey data regarding the extent of land contamination may be found in IAEA (2015;
figure 4.4, from end of April 2011 up to November 2014) or on the NRA website10 (from 2011 to 2020).

3.2.2.

Remediation plans and targets

In August 2011 the Japanese Diet enacted the Act on Special Measures concerning the Handling ofEnvironmental Pollution by Radioactive Materials. The act establishes that the government will be incharge of the decontamination and provides explicitly that TEPCO will bear the costs of the programof remediation of the areas affected by the accident. The following two categories for the remediationof land were specified:
7.
Tritium is a radioisotope of hydrogen. When existing in the form of tritiated water (i.e. composition hydrogen-tritium-oxygen),
it is not accumulated in marine biota and shows a very low dose conversion factor. It therefore presents a very minor contribution
to radiation exposure to individuals.
8.
METI (2018), Briefing Session on the current status of Multi-nuclide removal equipment (ALPS) treated water at Fukushima
Daiichi Nuclear Power Station, www.meti.go.jp/english/press/2020/1028_002.html (accessed 15 February 2021).
9.
The radiation levels decay with time from the initial high levels. These annual exposures are conservatively estimated using
a constant assumed dose rate from initial hourly figures, without taking such decay into account.
10. NRA (2021), Airborne Monitoring Survey Results, https://radioactivity.nsr.go.jp/en/list/307/list-1.html (accessed
15 February 2021).

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CURRENT STATUS OF TECHNICAL AND POLICY RESPONSES TO THE ACCIDENT AT FUKUSHIMA DAIICHI• a Special Decontamination Area within a 20 km radius of the Fukushima Daiichi site and otherareas where annual doses above normal in the year after the accident were predicted to begreater than 20 mSv;

• an Intensive Contamination Survey Area where annual doses were predicted to be between
1 and 20 mSv.
The national government took responsibility for determining and implementing the remedialplans in the Special Decontamination Area, whereas the local government implemented plans in the
Intensive Contamination Survey Area.
A balance has to be struck in any remediation plans between i) lowering contamination, andhence radiation exposure to people in the affected area; ii) the time, risk and resources to reduce
contamination; and iii) the amount of waste created. Initially, the government set the local public
exposure target to 20 mSv per year, but after the public expressed concern, this was reduced to 1 mSv
per year11 (The National Diet of Japan, 2012). The targets set are onerous. The October 2013 IAEA
international mission to review the remediation work noted that the government should explain to
the public that an additional individual dose of 1 mSv/year due to the Fukushima Daiichi Nuclear
Power Plant is a long-term goal, and that it cannot be achieved e.g. solely by decontamination work
(IAEA, 2013). The IAEA review team considered, as did the international scientific community, that thestated targets were unrealistic and that an annual dose remaining under the value of 20 mSv/year
would represent a more appropriate balance of situational factors, being in line with international
standards and recommendations for protecting public health and safety.

3.2.3.

Progress in remediation

In the Special Decontamination Area, contaminated housing and other buildings are demolished, andthe contaminated lands are decontaminated by removing approximately 5 cm from the upper levelof soil. The soil and waste removed from off-site decontamination works in Fukushima Prefecture(removed soils) are stored in an Interim Storage Facility (ISF) just outside of the Fukushima Daiichi
site on land acquired for this purpose until the time of final disposal. As a result of remediation
efforts, the decontaminated land has been gradually returned to use, many evacuation orders havebeen lifted, and people have been encouraged to return. Aside from Difficult to Return Zones (DRZ),
the Japan Ministry of the Environment (MoE) completed the decontamination work in the Special
Decontamination Area as planned at the end of March 2017. In DRZ, every municipality designatesa certain area as Special Reconstruction and Regeneration Bases, in which the national government
conducts an additional decontamination campaign. Six areas are currently designated as such since2017. In the Intensive Contamination Survey Area, the survey campaign was completed in March 2018.
Removed soils from this area of Fukushima are stored in the ISF until the time of final disposal.

3.3.

Significant technical and non-technical issues

The following sections build upon the general decommissioning status presented above and focus on
current and anticipated issues that are technical, logistical, or socio-political and non-technical in nature.

3.3.1.

Decontamination of the Fukushima Daiichi site

As decontamination activities continue on the Fukushima Daiichi site new problems may arise. The
way in which contamination can move across a site underground has been shown in other sites tobe complicated by legacy site construction elements that are no longer in use, such as old roadways,
abandoned piping, sealed off rooms and undocumented tunnels. International collaboration may
usefully assist with anticipating and addressing the technical challenges, through for example
compiling a database of techniques and experiences.
11. The exposure targets cited have a basis in international guidance. 20 mSv per year corresponds to the upper bound of referencelevel recommended by ICRP Publication 146 (ICRP, 2020) for existing exposure situations such as areas in post-accident recovery.

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CURRENT STATUS OF TECHNICAL AND POLICY RESPONSES TO THE ACCIDENT AT FUKUSHIMA DAIICHI

3.3.2.

Radioactive water treatment and management and the tritium issue

The water reduction engineering measures noted above have been very effective in reducing theaccumulation of contaminated water. However, the ion exchange technology used in the water
treatment process produces an additional waste stream of radionuclide-contaminated slurry andspent adsorbent which require interim storage and ultimate disposal. While the disposal of such waste
has yet to be resolved experience exists in other countries of applying solidification processes, thereby
putting the waste into a more passively safe form.
Treated water still remains one of the most challenging sources of on-site risk owing to residual
radioactive contamination, essentially due to tritium. There are no particularly effective andeconomical means of removal of tritium from water especially in large quantities and in relatively low
concentration. The tank farm of accumulated treated water, around 1.2 million cubic metres, occupies
a growing area of land that is needed for other decommissioning activities such as interim storageof decommissioning-related wastes. It also consumes resources that might otherwise be used fordecommissioning. There is little land left for the storage of further water.
A government advisory committee has reported (METI, 2020a) on handling methods for the tritiumcharged water and has advised that there are two technically feasible methods – vaporisation andrelease to the atmosphere, and discharge to the oceans after suitable dilution to ensure the release iswell within safe discharge concentrations. The scientific assessment is that such disposal to the airand oceans is no more than one thousandth of the exposure impact of natural radiation. However,
it is thought that any release has the potential to create public mistrust or lack of confidence
regarding both government decision making and the safety of food products (mainly the marine andbottom feeding fishes). Consultation is ongoing to conclude on the preferred handling method. The
transparency of the consultation on how to handle tritiated water could be enhanced through the
involvement of international experts, including those of neighbouring countries.

3.3.3.

Fuel removal from SFPs

The large inventory of radioactivity in the nuclear fuel assemblies stored in the pools in reactor
buildings Units 1 through 4, and the damaged state of the reactor buildings as a result of the hydrogen
explosions in Units 1, 3 and 4, made spent fuel removal from SFPs a priority. This has the aim of reducing
Fukushima Daiichi site risks by transferring spent fuel from SFPs in the buildings to the common poolwhich is more reliable. The removal of spent fuel from the SFPs has proceeded slowly but methodically.
The work was completed in December 2014 for Unit 4 and on 28 February 2021 for Unit 3. Significant
building debris had to be removed first from the SFPs, along with damaged fuel handling equipment.
Fuel removed from the damaged units is stored in the large common pool where some fuel willsubsequently be placed in dry cask storage units.12 The SFPs in each reactor building also store
damaged assemblies and highly irradiated and aged components, such as control blades, channel
boxes and fuel support pieces, which add additional complexity to removal and storage processes.
Emerging risks have been managed and workflow has been adjusted to accommodate new information
regarding high dose rate areas and special debris handling requirements. Such new information
sometimes requires work stoppages, situational evaluations, and placement of mitigating measures tomanage risk optimally over the anticipated long duration of decommissioning activities.

3.3.4.

Fuel debris removal from reactors

There are many challenging and novel aspects of decommissioning a nuclear site that has experienced
the meltdown of three reactors, where the containment buildings are compromised, fuel materials
melted and relocated, building structures are potentially compromised, and the site itself is
contaminated from the release of fission products. The removal of the melted and relocated reactor
fuel materials constitutes the most complex and hazardous technological challenge. First-of-a-kind
technologies must be developed to address the extreme challenges of radioactive materials, unknown
fuel debris properties, and environmental damage.
12. Part of new fuel (fresh fuel assemblies never used) is planned to be transported to a fuel manufacturer.

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CURRENT STATUS OF TECHNICAL AND POLICY RESPONSES TO THE ACCIDENT AT FUKUSHIMA DAIICHIThe experimental retrieval described in section 3.1.3
will provide knowledge and experience to provide afirmer basis for full-scale retrieval. Moreover, a great dealof scientific research and analysis has been undertaken,
notably in benchmarking exercises and other studies
initiated by the NEA. Outcomes will assist in anticipating
and addressing challenges that may be encountered during
the planned debris removal activities. The research andbenchmarking activities furthermore are contributing toworldwide understanding of severe accident progression
and the improvement of modelling and codes (NEA, 2015k;
forthcoming m).

3.3.5.

Solid waste management on site

Fuel debris inside the primary containment
vessel in the Unit 2 reactor building of the
Fukushima Daiichi Nuclear Power Plant. (Fueldebris is a substance that has cooled andre-solidified while being mixed with various
materials after the fuel in the reactor melted
as a result of the accident.) The debris can beremoved with a robot replicating the grip andmovement of fingers. Source: TEPCO Holdings

Currently, areas of the Fukushima Daiichi site arededicated to the temporary storage of various wastes
such as concrete rubble, as well as newer vegetive mattersuch as trimmed trees. Solid waste streams currently
exist for items such as contaminated clothing and soil. As
noted above, an important solid waste stream is contaminated slurry and spent adsorbent from thecampaign to decontaminate water of radioactive caesium and strontium. Radionuclide-contaminatedslurry and spent adsorbent currently are being retained on site.
In the years to come, additional solid waste streams and other waste storage needs will be
generated from new activities such as planned on-site facilities for incinerating combustible waste.
Ultimate disposal remains a distant objective at this point.

3.3.6.

Decontamination of off-site lands

Although much remediation work has been effectively completed, further attention is needed
regarding the means for regulation and final disposal of removed soils. Table 3.1 provides some details
on the amounts of wastes removed from the Special Decontamination Areas (SDAs) and Intensive
Contamination Survey Areas (ICSAs) in the course of clean-up, and the volumes of materials that havebeen moved from Temporary Storage Sites (TSS) to the Interim Storage Facility (ISF) or other means ofwaste management such as incineration or recycling, as well as the associated costs.

Workers decontaminating a residential garden in Okuma Town (photo taken in March 2016). Source:
Decontamination archive site, http://josen.env.go.jp/archive/detail/?OK-01-P0022

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Table 3.1: Volume of soils removed from off-site locations and evacuatedand costs associated with clean-up of SDA and ICSA (March 2018)
Classified
area

Volume of soils
removed (million m3)

Decontamination
cost (EUR billion)

Volume of soils
evacuated by recycling or
incineration (million m3)

9.1
7.9
17.0

12.6
11.8
24.4

1.62
1.20
2.82

SDA
ICSA
Total
Source: NEA (forthcoming h).

3.4.

Restructuring the nuclear legal framework in Japan

3.4.1.

Reorganisation of regulatory and preparedness systems

One of the fundamental principles for ensuring nuclear safety within a country is the effective
independence of the nuclear regulator, that is organisational, cultural, financial and politicalindependence from both the nuclear industry and those parts of government that sponsor the
nuclear industry (NEA, 2014a; forthcoming a; IAEA, 2006). A major lesson drawn from analysis of the
Fukushima Daiichi accident was the importance of independent regulation of nuclear safety, not only
structurally but also culturally (The National Diet of Japan, 2012).
Prior to 2012, the authorities responsible for the regulation of nuclear safety were the Nuclear
Safety Committee and the Nuclear and Industrial Safety Agency. The latter was organised under METI
which itself was responsible for the nuclear industry. To ensure a transparent separation of these
two sectors, nuclear safety regulation was decoupled from METI. Following the Fukushima Daiichi
accident, the Japanese government established in 2012 a new nuclear regulator with organisational
and political independence, the NRA, as an external agency of the MoE with the mission to protect
the general public and the environment through rigorous and reliable regulation of nuclear activities.
The NRA assumes the roles and responsibilities of nuclear safety and security regulations for nuclear
facilities and radioactive materials, as well as for nuclear non-proliferation safeguards. Formerly thesewere shared among several governmental organisations.
The NRA has faced a tremendous task not only in regulating the decommissioning of Fukushima
Daiichi and the restart/decommissioning of the reactors shut down after the accident, but crucially inbuilding a new independent expert regulatory body in a challenging environment. It has undergone
an extensive period of development and will need to continue to develop and adapt given thechanging circumstances. Initiatives to introduce new ways of working to the organisation include arisk-informed, performance-based reactor oversight process. Both the NRA and plant operators are
becoming more familiar with this new process, including the effective interactions and discussions
essential to implementing this new approach to regulation.
Based on the experiences and lessons learnt from the Fukushima Daiichi accident, the Japanese
government furthermore revised the Atomic Energy Basic Act, the Nuclear Emergency Act, and related
legislation in September 2012 to develop new nuclear accident emergency responses. A Nuclear
Emergency Preparedness Commission was established within the Cabinet, with the Prime Minister
serving as the Chairperson and the Chief Cabinet Secretary, the Minister of the Environment, and the
NRA Chairperson serving as Vice Chairpersons. The goal of the Commission is to ensure unified nuclear
emergency response policies are part of the routine work of the entire government. The Revision of
the Nuclear Emergency Act enhanced measures to prevent nuclear disasters and strengthened thefunctions of the Nuclear Emergency Response Headquarters in any emergency.

3.4.2.

Regulatory safety enhancements

When the NRA was established in 2012, it started to develop new regulatory requirements
incorporating lessons learnt from the Fukushima Daiichi accident. The new requirements, whichwere enforced in July 2013, focused mainly on strengthening the assessment of natural hazards and

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CURRENT STATUS OF TECHNICAL AND POLICY RESPONSES TO THE ACCIDENT AT FUKUSHIMA DAIICHI

establishing countermeasures to severe accidents. The measures accommodated by utilities included:i) measures to improve plant robustness and protection against tsunamis, including the installationof coastal levees, watertight doors and waterproofing of outside walls of buildings; ii) means to injectwater following a station blackout, and alternative power sources (such as air-cooled gas turbine
generators placed at a higher elevation); iii) supplemental battery capacity; iv) additional water
reservoir sources for plant makeup water; and v) to mitigate core damage, the installation of top-ventfacilities on reactor buildings, and filtered containment vent facilities.
Further, the new regulatory requirements reorganised the emergency-response organisations inJapan such that they are staffed and equipped to respond to simultaneous accidents in two or morereactors. The new regulatory requirements also require operators to construct backup facilities (aSpecialised Safety Facility and a permanent DC power supply facility as the third power system) tofurther enhance reliability. These facilities were required to be operational within five years from thedate of approval of the associated construction plan.

3.4.3.

Efforts to improve the nuclear liability framework

Although Japan was not a party to any of the international nuclear liability conventions at the time of
the accident,13 its Act on Compensation for Nuclear Damage provided for the basic principles includedin those conventions, such as the strict and exclusive liability of the nuclear operator for the nuclear
damage caused to third parties and the obligation to maintain a financial security (such as insurance)
to cover such liability.14 Japan is one of the few countries providing for the unlimited liability of thenuclear operator. The Act on Compensation for Nuclear Damage, coupled with innovative mechanisms
adopted to supplement it, fulfilled the purpose of allowing the nuclear operator, TEPCO, to compensate
victims in a timely and adequate manner. Those innovative mechanisms are as follows:• In August 2011 the Nuclear Damage Compensation and Decommissioning Facilitation
Corporation (NDF)15 was set up to provide under certain conditions financial support to Japanese
nuclear operators in case they face nuclear damage compensation obligations beyond therequired financial security amount of JPY 120 billion. As of 12 February 2021, TEPCO has paid
almost JPY 10 000 billion.16• Guidelines were drafted by the Dispute Reconciliation Committee for Nuclear Damage

Compensation (DRC), established under MEXT, to define specifically the types of nuclear damage
that would entitle to compensation and to assess the appropriate compensation for a given typeof damage.17• Voluntary out-of-court settlement of disputes relating to nuclear damage compensation claims

were promoted by the Nuclear Damage Compensation Dispute Resolution Centre (ADR Centre),established by the DRC.18 Most disputes have been settled out of court.19

13. On 15 January 2015, Japan deposited its instrument of acceptance to the 1997 Convention on Supplementary Compensation
for Nuclear Damage (CSC). The CSC entered into force for Japan on 15 April 2015. The reasons that led Japan to join thisConvention are as follows: i) the need to adopt an international nuclear liability regime; ii) the need to address the legal concernsof the foreign suppliers participating in the decommissioning of the TEPCO Fukushima Daiichi Nuclear Power Plant; iii) the accessto the CSC international fund; and iv) the improvement of the legal framework applicable to nuclear trade.
14. For more detailed information on the Japanese nuclear liability regime applicable at the time of the accident, see Japan’sCompensation System for Nuclear Damage: as Related to the TEPCO Fukushima Daiichi Nuclear Accident (NEA, 2012c).
15. The Nuclear Damage Compensation Facilitation Corporation Act was amended in May 2014 and became the “Nuclear
Damage Compensation and Decommissioning Facilitation Corporation Act” to include the decommissioning of the TEPCO
Fukushima Daiichi NPP among the Corporation’s activities.
16. TEPCO (2021), Records of Applications and Payouts for Compensation of Nuclear Damage as of 12 February 2021, www.
tepco.co.jp/en/hd/responsibility/revitalization/pdf/comp_result-e.pdf (accessed 15 February 2021).
17. Guidelines from the DRC were introduced in the Act on Compensation for Nuclear Damage in 2009 following the 1999
Tokaimura nuclear accident.
18. The ADR Centre at one point in time employed more than 400 attorneys.
19. According to the written report of TEPCO to the DRC, about 2 941 000 applications for compensation were received by
the end of July 2020, while 567 lawsuits were filed against TEPCO before the courts. Among these lawsuits, 165 cases are still
pending. Source: TEPCO (2021), “Situation of the payouts of nuclear damage compensation and other information”, www.mext.
go.jp/content/20200924-mxt_san-gen01-000010296_03.pdf (accessed 15 February 2021).

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CURRENT STATUS OF TECHNICAL AND POLICY RESPONSES TO THE ACCIDENT AT FUKUSHIMA DAIICHI• The three-year discovery period was extended to ten years.20
In December 2018, the Act on Compensation for Nuclear Damage was amended21 to introduce thefollowing changes that entered into force on 1 January 2020 and had already been implemented for the
Fukushima Daiichi accident:• Nuclear operators will have to publish their general policy to compensate nuclear damage,which should include a description of the claims handling process, of the financial security
coverage and of the dispute resolution mechanism.22• A governmental loan up to the amount of the operator’s financial security (i.e. JPY 120 billion foreach nuclear power plant site) will be available to promote the prompt payment of provisional
compensation by the liable nuclear operator.

• The discovery period will be suspended during the mediation procedure of the ADR Centre.
These changes aimed at ensuring legal preparedness and the adequate and prompt compensationof potential victims in the future.
Finally, at the time of the accident Japan had not joined any of the international nuclear liability
conventions; therefore it had no such treaty relations with other states,23 including the United States,with regard to nuclear liability. A number of lawsuits have been filed by American and Japanesecitizens before US courts against American suppliers and TEPCO. At the time of publishing this report,
some of these suits have been dismissed by the courts, while others are ongoing.24 This demonstrates
the legal risks that may arise when countries are not in treaty relations that clearly establish which
nuclear liability regime would apply in case of an accident.

20. Pursuant to Article 724 of the Civil Code, all rights of action are fully extinguished 20 years (prescription period) following
the date of the tort (i.e. the nuclear accident) and the actions must be brought by the victims within three years (discovery period)
from the date on which the person suffering damage had knowledge or should have knowledge of both of the damage and of theperson liable (i.e., the operator of the nuclear installation where the accident occurred). In May 2013, the Act on the Interruptionof Statute of Limitations for Settlement Mediation Procedure in the Dispute Reconciliation Committee for Nuclear Damage
Compensation suspended the three-year discovery period and in December 2013, the Act on Sure and Prompt Compensation and
the Special Exception on the Statute of Limitations for the Damage Caused by Nuclear Accident in 2011 extended the three-year
discovery period to ten years. Both Acts are special acts that only apply to the Fukushima Daiichi accident.
21. Article 6 of the supplementary provisions to the Nuclear Damage Compensation Facilitation Corporation Act, enacted
on 3 August 2011, obliged the government to establish an organisation to facilitate the process of resolving disputes. It also
demanded the government to consider drastic revision of the Act on Compensation for Nuclear Damage.
22. TEPCO (2021), Records of Applications and Payouts for Compensation of Nuclear Damage as of 12 February 2021, www.
tepco.co.jp/en/hd/responsibility/revitalization/pdf/comp_result-e.pdf (accessed 15 February 2021). In May 2013, TEPCO had
almost 11 000 persons handling the claims, which entailed hiring and training the staff, providing for the necessary office spaceand equipment, and implementing effective processes within a very short period of time.
23. If two countries join the same nuclear liability instrument, they will be considered to have “treaty relations” and the common
instrument will determine a number of legal issues, such as which nuclear liability regime would apply in case a nuclear accident
occurs in one of those countries to compensate the population of the other state (i.e. which would be the applicable law and thecompetent court).
24. For more information on these lawsuits, see NEA (2020), Nuclear Law Bulletin, No. 103, OECD Publishing, Paris, pp. 47-49.

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4. Safety improvements and otherlessons learnt at the international level
4.1.

Key activities and achievements of the Nuclear Energy Agency and member
countries

Shortly after the 2011 accident, significant joint studies were initiated by the Nuclear Energy Agency(NEA), member countries and, importantly, the government of Japan. These included a benchmark
study of the accident at the Fukushima Daiichi Nuclear Power Plant started in 2012, and postFukushima safety research started in 2013. Governments, regulators, technical organisations, operatorsand other stakeholders of the NEA and member countries, including Japan, moreover undertook
organised safety-enhancing activities in response to the accident at Fukushima Daiichi. In general,these activities have contributed to establishing a common understanding of the accident and led to
improved tools and a better quantification and understanding of plant safety margins.

State of the Unit 1 reactor building at the Fukushima Daiichi Nuclear Power Plant (photo taken in March 2021).
After a large cover is installed over the top of the building and rubble is removed, it is planned to start fuelremoval in the spent fuel pool in the fiscal years 2027 to 2028. Source: TEPCO Holdings

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Areas of study have included safety of multi-unit sites, the potential for common cause failuresthrough external events, and mechanisms important in accident progression including ex-vessel
phenomena. Potential improvements have been identified in several areas such as fuel designs that are
more tolerant of accidents and electrical power systems that are more robust. The NEA also organised
meetings and activities to learn lessons of public health aspects from the accident and share themwith member countries, with an important focus on stakeholder involvement in decision-making. The
reference section of this report lists pertinent NEA publications in these areas.

4.1.1.

Safety reviews

Comprehensive reviews were undertaken across NEA countries to enable an evaluation of the safety
and robustness of nuclear power plants, including evaluating their capacity to withstand major
incidents beyond the existing design-basis capabilities for external hazards. The reviews, which weregenerally based on existing and new safety studies, as well as engineering judgment, examined theadequacy of design-basis assumptions as well as provisions for conditions more severe than designbasis events. Each NEA member country used its own approach and methods for the reviews, althoughsome also conducted reviews within a regional framework (e.g. the European Stress Test Program).
The reviews generally covered similar initiating events (e.g. earthquake, flooding and other extreme
natural conditions challenging the specific site) and consequent or postulated loss of safety function(e.g. loss of electrical power, including station blackout [SBO]; loss of the ultimate heat sink [UHS]; or a
combination of both), as well as the capability to cope with severe accidents.
Although diverse approaches and methods were used for the reviews, individual NEA member
countries reached many similar conclusions regarding the needed safety improvements andenhancements. A shared insight is the need for diversity of equipment, enhancements in therobustness of safety functions and continuing efforts to improve organisational behaviour. Common
activities have included a focus on plant and process improvements to mitigate the potential
impact of external hazards. Areas under examination include: i) re-assessment of external hazards;ii) improvement of the robustness of the electrical systems; iii) an enhancement of the robustnessof the UHS; iv) protection of the reactor containment system, v) protection of spent fuel in spent
fuel pools (SFPs); vi) reinforced capability to rapidly provide diverse equipment and assistance fromon-site or off-site emergency preparedness facilities; vii) reinforced safety culture, including humanand organisational factors in decision making during emergencies; viii) continued safety research; andix) consideration of events that could affect all the reactors at a single site simultaneously (multi-unit
events). Many improvements have already been implemented in these areas.
Particularly in the context of safety culture, the Japanese industry, based on the lessons learnt
from the accident, established the Atomic Energy Association (ATENA) to voluntarily pursue further
safety enhancement potentially even beyond legal requirements. ATENA co-ordinates the activitiesof the entire nuclear industry and seeks to accomplish the higher level of safety for nuclear power
plants. In addition to ATENA, the Japan Nuclear Safety Institute (JANSI) and the Nuclear Risk ResearchCenter (NRRC) support nuclear operators through peer reviews of nuclear power plants and to conduct
fundamental research activities for safety improvements. The important commitments of the nuclear
operators and the industry to foster safety culture and to voluntarily pursue safety enhancementwith nuclear facilities are endorsed by the policy of the national government through Japan’s Strategic
Energy Plan in 2018.
In addition, governments in several countries have taken action to reinforce the independence of
their regulatory bodies.

4.1.2.

Cross-cutting safety research and analysis on severe accidents and decommissioning

Following the accident at the Fukushima Daiichi Nuclear Power Plant in 2011, NEA research projects
supported by participating member countries and the government of Japan, as well as other NEA joint
efforts, have delivered cross-cutting safety research. These initiatives support both decommissioning
research and development (R&D) activities in view of the extraction of fuel debris and waste
processing, and the improvement of scientific understanding and modelling capabilities addressing

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severe accident progression and consequences. Some studies in particular have analysed information
obtained from reactor buildings and containment vessels of Fukushima Daiichi Nuclear Power Plant.
Overall the activities have revealed valuable insights, identified near-term and long-term R&D topics,
and provided technical bases for planning decommissioning activities.
An analytical study in two phases has aimed at benchmarking internationally used severe
accident computer codes against the known data and behaviour of the three accidents of reactor
units 1, 2 and 3 (NEA, 2015k; forthcoming n). There were very encouraging results given the inherent
challenges of the analyses. These provided code-generated estimates of the damage to the reactor
fuel and the relocation and ultimate disposition of melted and relocated fuel materials which span
the regions between the damaged cores, the reactor pressure vessel (RPV) lower head and the primarycontainment vessel (PCV) cavity regions. These damage estimates suggest where fuel materials arelikely to be found and their likely compositions, and while these estimates likely differ from whatis ultimately found during decommissioning, the estimates are nonetheless valuable in planning
re-entry strategies and likely required fuel removal technologies and waste streams. Note that theseanalytical findings are also merged with other characterisations such as muon imaging of the reactors
to determine location for high density core materials (i.e. fuel) and in-PCV robotic investigations
which also provide information on fuel distribution end states to provide greater certainty concerning
decommissioning methods.
Analytic studies and fuel debris physical characterisations are essential elements of an informed
and efficient decommissioning campaign. With the support of the Japanese government, NEA
member country institutions and the European Commission’s Joint Research Centre (JRC) launched apreparatory study on the analysis of fuel debris. In follow-on activities, information derived from codeis aggregated with physical information from robotic entries into the damaged PCVs, to support fueldebris characterisation and planning for fuel extraction and removal.
Another joint project (NEA, forthcoming j), again supported by the Japanese government, hasenabled a deeper understanding of material behaviour in severe accident conditions, which will
ultimately contribute to the improvement of the severe accident mitigation strategies. Such studies
enable the improvement of reference thermodynamic databases and degradation models applied to
the Fukushima Daiichi accident.

4.1.3.

Characterisation and management of unconventional waste

Of radioactive waste resulting from the accident at the Fukushima Daiichi Nuclear Power Plant,
low-level and very low-level waste represent the vast majority by volume while making up only asmall fraction of the radiological inventory. An optimal approach to handling these large amounts
of so-called unconventional waste has not yet been settled. This is due to the lack of availability of
the appropriate long-term waste management infrastructure, which demands a robust process andprocedures for managing waste, waste disposal routes including the siting of disposal facilities, andappropriate safety culture as well as public acceptance.
As Japan pursues the clearance and release of the very low-level post-accident radioactive
waste in full respect of international standards, among the most difficult near-term challenges arecharacterisation and categorisation. An international activity (NEA, forthcoming k) examined how todevelop a complex waste characterisation process. Case studies from NEA countries including France,
Japan, the Russian Federation, Ukraine and the United Kingdom allowed the identification of strategic
components for such a process.
Although the prime responsibility for ensuring safe management of radioactive waste rests
with the operator, there is a need for the government to establish a basic framework for taking theinterests of stakeholders into consideration when making decisions. The establishment of a regulatory
framework and dialogues with stakeholders to implement the policy are encouraged; the framework
should afford flexibility to address uncertainty in characterising unconventional and legacy waste, andenable the weighing of variables and prevailing circumstances in complex decision making.
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4.1.4.

Stakeholder involvement

The accident at Fukushima
Daiichi transformed perceptions
regarding the role of citizens ingovernment decision-making
about nuclear energy, especiallyat the local level. In Japan and inseveral other countries, the accident
significantly undermined publictrust in governmental oversight of,and communication about, nuclear
energy. In some NEA member
countries, it underscored the needto take into account the knowledge,
values, interests and preferencesof concerned communities innuclear decision making, including
for accident preparedness andrecovery in affected areas. The years
after Fukushima Daiichi have seencontinued worldwide debate about
Workers handling storage containers for adsorbents used in equipment thatthe so-called “social licence” forpurifies water containing radioactive substances generated on the premises
nuclear energy-related decisions:of the Fukushima Daiichi Nuclear Power Plant. The used adsorbents are
stored and sealed in a robust container. Source: TEPCO Holdings“is this to be granted by duly elected or
appointed government officials, or bythose individuals and communities who will be directly impacted?” The accident had profound, wide-ranging
and long-lasting repercussions for local communities, highlighting the democratic deficit in making
consequential decisions without sufficient local ownership. In a trend started well before the 2011accident, reflected in such international treaties as the 1998 Aarhus Convention, stakeholders in NEA
member countries increasingly expect not merely to be informed about important environmental andinfrastructure decisions affecting their lives, but to be directly and meaningfully involved in making
those choices – beyond participating in democratic elections. In harmony with NEA work predating
Fukushima Daiichi, the NEA considers stakeholder involvement an essential process for making
sound and durable decisions. Lessons learnt from the accident at Fukushima Daiichi Nuclear Power
Plant clearly highlight a dimension of societal acceptance in decision-making through stakeholder
involvement. Earning trust is key for recovery.
Past practice demonstrates the feasibility of such engagement. In the aftermath of the accident at
the Three-Mile Island Nuclear Power Plant Unit-2 in 1979, the US Nuclear Regulatory Commission (NRC)
established a Citizen’s Advisory Panel which was active between 1980 and 1993 (USNRC, 1994). Thispanel provided opportunities for the public, regulator, and licensee representatives to meet periodicallyin a public forum to discuss clean-up issues, solutions and plans. In addition, through periodic public
meetings the panel helped maintain the NRC Commissioners’ awareness of the importance to thecitizens of the clean-up. Japanese government agencies have been holding meetings, public panels andadvisory group discussions with local stakeholders in the area of the Fukushima Prefecture.
Following the accident at the Fukushima Daiichi Nuclear Power Plant, the NEA transitioned fromdiscussing stakeholder involvement within the context of particular work areas to a holistic approach.
An initial report on stakeholder involvement in nuclear emergencies published in October 2011highlighted that sustainable post-accident recovery requires committed, long-term outreach to a rangeof stakeholders. Subsequently, growing recognition that stakeholder involvement in nuclear decisionmaking exists in a socio-political context of public trust and may extend beyond radioactive waste
management or emergency response prompted a wider berth. In 2017 and 2019, the NEA organised
stakeholder involvement workshops which integrated all NEA areas of international co-operation.
The workshops established the interconnectedness of decision making and risk communication withstakeholder relationships and trust for long-term nuclear energy programmes.

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4.1.5.

Country-specific safety culture enhancements and safety culture of the regulatory bodyAchieving and maintaining high levels of safety is the goal of all organisations involved in nuclear
energy. Experience has shown that a healthy safety culture is essential to the overall safety
performance of any organisation, and that safety culture is influenced by many factors including
national context. Two NEA workshops have explored organisational and national influences on nuclear
safety culture.
In 2018, the NEA and the World Association of Nuclear Operators (WANO) held a Country-Specific
Safety Culture Forum (CSSCF) in Sweden to explore the impact of the national context on nuclear
safety and identify approaches to sustain and improve nuclear safety culture. The forum demonstrated
that the national context has a powerful impact on nuclear safety, suggesting it will be important for
all countries to understand and potentially use the particular aspects present in their own cultures toenhance safety culture.
A separate workshop focussed on challenges and enhancements to the safety culture of theregulatory body was held in June 2015. The report (NEA, 2015j) emphasised that the manner in whicha regulator oversees the industry greatly affects the safety culture within that industry and hence
nuclear safety. Thus, the regulatory safety culture, which is the basis for its interactions with theindustry, is a vital component of assuring a high level of national nuclear safety. The report also
highlighted the influence that national culture can have on safety culture, emphasising that national
characteristics and cultural strengths should be recognised and used to foster and develop a healthysafety culture.

4.1.6.

Emergency and accident management

Off-site
The accident at the Fukushima Daiichi Nuclear Power Plant highlighted the importance ofeffective nuclear accident response, including reliable estimation of potential consequences andimplementation of actions as appropriate in response to the anticipated consequences. However, thecomplexity of the accident, combined with the widespread effects of the earthquake and tsunami,
greatly impacted the ability to provide timely and accurate information to national and international
stakeholders. In fact, as stated in a NEA report (NEA, 2015c), organisations involved in the assessmentof potential consequences from the Fukushima Daiichi accident in 2011 were predicting different
outcomes, which occasionally led to a lack of clarity, delays in taking action or a non-optimised
response. Regarding initial decisions on urgent protective actions, the arrangements in Japan wererevised after the accident so that actual conditions at the nuclear power plant constitute the basis
for taking urgent protection actions, rather than using dose projection models.1 It was also observedthat the measures given by many foreign governments to their citizens residing or staying in Japanoccasionally differed, especially at the initial stages of the accident. Such variations, which may be
attributed to factors such as the methods used to assess accident progression and to develop estimatesof radionuclide releases to the environment, can affect the projected radiological dose to a member ofthe public.
NEA experts in the field of radiological protection and public health recently pointed to postaccident recovery management as an important pillar of ensuring public well-being. It is seen as acomplex multidisciplinary process of multisectoral dimension, and all the NEA member countries
have expressed the need for international co-operation to improve preparedness for recovery. (Further
consideration is given in section 5.2.)

Emergency operating procedures (EOPs) and severe accident management guidelines (SAMGs)
In June 2012, the NEA’s task group on accident management assessed member country’s regulatoryneeds and challenges in light of the Fukushima Daiichi Nuclear Power Plant accident. The group
1.

Callen and Homma, 2017.

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identified measures that should be considered to enhance the regulations and regulatory guidance for
operators’ accident management activities.
In addition, the NEA Working Group on Analysis and Management of Accidents developed a reportto address the topic of severe accident management guidelines (SAMGs) verification and validation,with a particular focus on the use of analytical simulations as one of the means to inform SAMGs innuclear power plants. The report describes the current practices to ensure the correctness, adequacy,
usability and efficiency of SAMGs, provides an overview of national examples of past and ongoingassessments of severe accident management (SAM) and summarises recommended practices withregard to the use of analytical simulations. That being said, every accident is likely to be unique andhence an overriding message is that SAMGs need to be flexible and focused on the basics rather thanon detailed responses to a particular accident sequence.

Radiological protection for severe accident management
In 1992, the NEA and the International Atomic Energy Agency (IAEA) began to jointly sponsor the
Information System on Occupational Exposure (ISOE) to foster the exchange of data, analysis, lessons
learnt and experience in occupational radiological protection at nuclear power plants worldwide.
Following the Fukushima Daiichi accident, the ISOE focused on identifying the experienceand information from the Chernobyl and Three Mile Island (TMI) accidents, looking at how the
management of emergency worker/responder doses were legally and practically managed, as well as
information about personal protective equipment for highly contaminated areas. This information
was collected from the ISOE-participating nuclear utilities and regulatory authorities and madeavailable for Japanese utilities. In May 2011, an expert group was established to discuss occupational
radiological protection in severe accident management.
A report (NEA, 2014m) compiled best practices in radiological protection job coverage during
response to a severe accident and identified the following major issues that should be considered
and incorporated into an occupational radiological protection program: i) the development ofextensive emergency response plans to protect emergency workers/responders and the public; ii) the
development of anticipatory training related to severe accident management for all emergency
workers/responders; iii) the effective implementation of a radiological protection programme during asevere accident (as this may be significantly impacted by the plant’s facility configuration and access
controls); iv) radiological protection of the emergency worker/responder, including the establishmentof individual exposure reference levels, extensive work controls, and thorough radiological exposure
controls to maintain emergency worker/responder radiation exposures as low as reasonably
achievable (ALARA); v) extensive radiological controls of radioactive and contaminated materials
released internally and externally from the affected facility during the emergency and post-accident
mitigation phases to avoid or minimise radiation exposures to emergency workers/responders andthe public; and vi) comprehensive emergency plan development, routine training and exercising(including stressful, time-limited activities) of all emergency workers/responders, remote radiologicalmonitoring, high dose detection equipment, and robotic equipment.

Long-term accident management
Prior to the accident at the Fukushima Daiichi Nuclear Power Plant, the need for long-term accident
management had not been foreseen. It was anticipated that some form of short-term intervention
would be possible to stabilise the situation (e.g. reintroduction of off-site power).
Accident management exercises have typically been run as “tabletop exercises” of management
strategies during some 24 hours of accident “simulation,” after which the accident is typically declaredconcluded. The reality experienced at Fukushima Daiichi Nuclear Power Plant was that an accident
lasts more than 24 hours, and indeed, must be managed over many months, and even years following
the initial occurrence of the accident.

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In a March 2000 report on the impact of short-term severe accident management actions in a longterm perspective (NEA, 2000), a survey of international practices was made with the aim of identifying
means of preventing further plant damage and optimising long-term accident management. This
study identified actions such as measures to preserve long-term containment function and means of
mitigating long-term releases that are further reinforced by real-world experience at the Fukushima
Daiichi Nuclear Power Plant. One action considered by the Boiling Water Reactor Owners Group isreferred to as “anticipatory containment venting2”.
A report on accident management of regulatory aspects reflected on insights for long-term
accident management learnt from the accident at the Fukushima Daiichi Nuclear Power Plant (NEA,
2014j). This study describes the concept of integrated accident management (IAM) as a generalisationand extension of the reactor accident SAMGs that seeks harmonious optimisation of safety
management, risk reduction, prevention and mitigation for all aspects of the Nuclear Power Plant
including SFPs and interim waste management. This aim is approached from the standpoint of:i) procedures and guidelines, ii) equipment, components and instrumentation, and iii) human andorganisational resources.
With respect to procedures and guidelines, the study recommends accident management
procedures for all plant operating states such as full power, low power or shutdown, including SFPs
taking consideration of portable equipment and improvised mitigations. Concerning equipment,
components and instrumentation, a major challenge in long-term management is understanding
plant status as indicated by potentially defective or damaged instrumentation and ability tomonitor and manage the site from the main control room over varying conditions throughout
the decommissioning duration and under potential future accident or external event challenges.
Finally, the training and staffing of the long-term accident management infrastructure is a multigeneration requirement over the anticipated 30 years needed to complete decommissioning work.
This is a challenging extension of accident management training given the already extensive training
demands posed by other safety aspects such as training for emergency operating procedures. This
field of safety practice has been furthered by the NEA activities undertaken since the Fukushima
Daiichi accident.

4.1.7.

Oversight for safety

Defence in depth
In June 2013, a joint NEA workshop considered the core theme of defence in depth (DiD). The
participants examined key priorities for the application of the DiD concept and identified important
topics to pursue in order to strengthen the application of DiD. The main conclusions were that theDiD concept remains valid, but strengthening and further work on implementation may be needed.
A Regulatory Guidance Document on DiD (NEA, 2014i) was therefore developed, which identifies areas
for further study including:

•
•
•
•
•

the impact of human and organisational factors on DiD;
improvements on the use of the DiD concept for multi-unit sites, fuel cycle facilities and research;
reactors and new reactor designs;
implementation of countermeasures for level 5 of DiD;
benchmarking and further harmonisation of the regulatory use of DiD through training,
workshops and other means;• the impact of new technologies.
2.
Anticipatory containment venting is a short-term accident management procedure to relieve the containment of steampressure in the development of a severe accident before fuel damage and fission product release to the containment has takenplace. Such action is taken to preserve containment safety margins and functionality at a later time when fission products andhydrogen are present and to ensure the many low pressure water injection sources do not encounter containment pressures thatexceed the shutoff head of systems like fire suppression systems.

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Characteristics of an effective regulator
In June 2012, regulatory experts gathered by NEA agreed that effective regulatory organisations are thosethat have good leadership and are able to transform strategic direction into operational programmesthat achieve its fundamental purpose: ensuring that licensees operate their facilities and discharge
their obligations in a safe manner, in accordance with international safety principles and with fullrespect of the environment. The report (NEA, 2014a) stated that an effective nuclear safety regulator:• is clear about its regulatory roles and responsibilities, its purpose, mandate and functions;• has public safety as its primary focus;• has independence in regulatory decision making from any undue influence on the part of thenuclear industry and those sectors of government that sponsor this industry;• has technical competence at its core, with other competencies built upon this fundamental andessential requirement;• is open and transparent in its regulations and decisions;• has a regulatory framework and requirements that are clear and easily understood by all
stakeholders;• makes clear, balanced and unbiased decisions, and is accountable for those decisions;• has a strong organisational capability in terms of adequate resources, strong leadership androbust management systems;• performs its regulatory functions in a timely and efficient manner;• has and encourages a culture of continuous self-improvement and learning, including thewillingness to subject itself to independent peer reviews.

4.1.8. Nuclear law
Since the occurrence of the accident, the Japanese delegation has been providing briefings at eachmeeting of the NEA Nuclear Law Committee (NLC) on the implementation of the Japanese legal
framework and the legislative innovations. Dedicated sessions have regularly examined the legal
framework and the actual implementation of Japan’s compensation scheme in order to draw lessons
for the benefit of the international community.
The Japanese government, in co-operation with the NEA Secretariat, prepared Japan’s Compensation
System for Nuclear Damage: As Related to the TEPCO Fukushima Daiichi Nuclear Accident (NEA, 2012c). Thispublication gathers the English translations of all major statutes, ordinances and guidelines adopted
or issued by the Japanese government in order to establish and implement the compensation scheme
necessary to respond to the Fukushima Daiichi nuclear accident, as well as several commentaries.

Encouraging broader adherence to the international nuclear liability conventions
Since the Fukushima Daiichi accident, the international community has encouraged broader
adherence to the international nuclear liability conventions with the goal of achieving a global nuclear
liability regime (IAEA, 2011; NEA, 2011d). Broader adherence would lead to greater harmonisation ofnational nuclear liability and compensation schemes, and thus promote a more similar treatmentof victims and operators on a worldwide basis. In addition, greater adherence to any one of theinternational nuclear liability regimes would result in the extension of treaty relations between states,
providing greater certainty both to nuclear industry investors and suppliers as well as to the generalpublic regarding the liability regime that would apply in case of an accident.
The IAEA General Conference in September 2011, through its Action Plan on Nuclear Safety, and the
NEA Steering Committee at its policy debate on “Progress Towards a Global Nuclear Liability Regime”
in April 2014, encouraged their respective member countries to adhere to one of the nuclear liability
regimes and to adopt consistent legislation, if they have not already done so.
The nuclear liability principles were implemented for the first time to compensate victims of asevere accident following the Fukushima Daiichi nuclear accident. If the legal framework demonstrated
its effectiveness, it also revealed that the international community needed to continue exploring thepractical application of the nuclear liability regimes.

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SAFETY IMPROVEMENTS AND OTHER LESSONS LEARNT AT THE INTERNATIONAL LEVELThe NEA organised for that purpose two international workshops:• the Third Workshop on the Indemnification of Damage in the Event of a Nuclear Accident

in 2017, which assessed the challenges of implementing the international nuclear liability
conventions in case of a transboundary accident;• the Fourth International Workshop on the Indemnification of Damage in the Event of a Nuclear

Accident in 2019, which addressed the challenges of determining nuclear damage in practice,and of setting up a national or transboundary claims handling.

Workers performing maintenance on tanks for storing ALPS treated water installed on the premisesof the Fukushima Daiichi Nuclear Power Plant. Source: TEPCO Holdings

4.2.

Key activities and achievements of other international organisations

This section identifies the main international organisations aside from the NEA that have been
directly affected or involved in the response to the accident at Fukushima Daiichi, and summarises
their undertakings in the past 10 years. This short summary is purely the view of the NEA and is notintended to substitute for the publications of specific international organisations.
The IAEA is a United Nations body with 172 member countries. It was created in the late 1950s as ameans to support the safe and responsible use of nuclear technology. The IAEA’s best-known mission is
to implement the global non-proliferation regime to limit the spread of nuclear weapons, but it is also
very active in the nuclear safety area. The IAEA provides assistance to countries newly entering thenuclear sector, conducts peer review missions, and publishes consensus safety standards that member
states may use as references in establishing national regulations. The IAEA partners with the NEA andother international bodies to develop reports and analyses and to organise international conferences.
The primary role of the World Health Organization (WHO) is to direct international health within
the United Nations system and to lead partners in global health responses. Membership in the WHO is
open to all member countries of the United Nations.
The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) is mandated
to undertake broad assessments of the sources, effects and risks of exposure to ionising radiation fromhuman health (public, patients, workers) and the environment. In pursuit of its mandate, UNSCEAR
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thoroughly reviews and evaluates global and regional exposures to radiation. UNSCEAR also evaluates
evidence of radiation-induced health effects in exposed groups and advances in the understandingof the biological mechanisms by which radiation-induced effects on human health or on non-humanbiota can occur. Those assessments provide the scientific foundation used, inter alia, by the relevant
agencies of the United Nations system in formulating international standards for the protection of thegeneral public and workers against ionising radiation; those standards, in turn, are linked to important
legal and regulatory instruments.
The International Commission on Radiological Protection (ICRP) consists of eminent scientists,
policy makers, practitioners, and other experts in the field of radiological protection. All members of
the Main Commission, Committees, and Task Groups are volunteers, selected through a transparent
process. The ICRP was established to advance the science of radiological protection for the publicbenefit, in particular by providing recommendations and guidance on all aspects of protection against
ionising radiation.
WANO brings together every operator of commercial nuclear facilities in the world to co-operate inassuring that all nuclear plants strive for the highest standards of nuclear operations excellence andnuclear safety. It has over 120 members from all over the world.

4.2.1.

Activities and achievements of the IAEA

Following the accident at Fukushima Daiichi, the IAEA engaged in dialogue with Japanese officials
regarding on-site and off-site issues. The on-site assistance included: an International Fact-finding
Mission in May-June 2011; four International Peer Review Missions in 2013 (twice), 2015 and 2018; and a
Follow-up Review in 2020. The off-site assistance included: i) two international peer review missions in2011 and 2013; and four IAEA-Ministry of Environment Experts Meetings (two each in 2016 and 2017).
In 2011, the IAEA efforts focused on crisis management and understanding the emergency situation.
Subsequent focus turned to stabilisation, storage of treated water, and creating a safe, predictable
work environment. Ongoing efforts include focusing on decommissioning, solving the accumulationof treated water, removing spent fuel and debris, and planning for the next 50 years.
From the four IAEA Peer Review missions to Japan, the agency acknowledged significant
improvement in working conditions at the site, water management and solid waste management. The
missions also identified good progress towards removing spent fuel from the three damaged reactors,
as well as progress in understanding the status of fuel debris in the reactors. The advice shared withJapanese counterparts following the missions included: i) the need for a decision on the disposition
path for accumulated treated water; ii) preparation of an integrated plan for the completion of
decommissioning, including waste treatment and management; iii) strengthening decommissioning
and decontamination project management; and iv) the value of drawing upon the global diversity ofinternational good practices. Other relevant ongoing IAEA work associated with the decommissioningof Fukushima Daiichi includes the Decommissioning and Remediation of Damaged Nuclear Facilities(DAROD) Project and the Coordinated Research Project (CR) on Management of Severely Damaged
Spent Fuel and Corium.
Of particular note is the IAEA’s comprehensive and detailed international technical review of theaccident involving a very large number of international experts (The Fukushima Daiichi Accident – Reportby the Director General, [IAEA, 2015]).

4.2.2.

Activities and achievements of other United Nations bodies

World Health Organization (WHO)Immediately after learning of the accident at Fukushima Daiichi, the WHO activated its emergency
response procedure including liaison with the IAEA. WHO personnel worked to assess public healthrisks and provide technical assistance. WHO’s response was supported by its Radiation Emergency
Medical Preparedness and Assistance Network to provide authoritative advice on radioactive
contamination and food consumption and trade. The WHO also provided travel advice and information
on potential radiation risks to its member countries, the public and the media.

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United Nations Scientific Committee on the Effects of Atomic Radiation
UNSCEAR issued a report on its 2013 assessment of the radiation exposures of the public, workers andnon-human biota from the accident at Fukushima Daiichi and concluded that health risks resulting
from the accident were far lower than those for Chernobyl (UNSCEAR, 2014). This assessment was dueto the substantially lower doses received by the public and workers in Japan. The report also indicatedthat UNSCEAR did not expect discernible increased incidences of radiation-related health effects
among those exposed.
UNSCEAR then published White Papers (UNSCEAR, 2015; 2016; 2017) covering six thematic areas:i) radionuclide releases to atmosphere, dispersion and deposition; ii) radionuclide releases to water,
dispersion and deposition; iii) evaluation of doses for public; iv) evaluation of doses for workers;v) health implications for workers and public; and vi) evaluation of doses and effects for non-humanbiota. In its 2016 White Paper UNSCEAR also considered a new topic: the transfer of radionuclides interrestrial and freshwater environments (UNSCEAR, 2016) An updated assessment of the levels andeffects of radiation exposure due to the accident at the Fukushima Daiichi Nuclear Power Plant is inpreparation (UNSCEAR, forthcoming).

4.2.3.

Activities and achievements of the ICRP

After the Fukushima Daiichi Nuclear Power Plant accident, the ICRP compiled initial lessons related
to the system of radiological protection. The ICRP is already taking action on this basis, including
developing dose conversion coefficients for external exposures to environmental sources, andupdating advice on emergency and existing exposure situations.
In late 2011 ICRP began a Dialogue Initiative between experts, authorities, professionals, NGOs,
local communities and representatives of Belarusian, Norwegian and French organisations withdirect experience in managing long-term consequences of the Chernobyl accident, to find ways torespond to the challenges of the long-term consequences of the Fukushima Daiichi accident. The NEA
supported and participated in these dialogues and applied many important lessons into its work on
stakeholder engagement.

High-pressure cleaning to decontaminate the pavement surface outside the Iitate Junior HighSchool building in Iitate Village (photo taken in July 2016). Source: Decontamination archive
site, http://josen.env.go.jp/archive/detail/?IT-01 -P0038

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SAFETY IMPROVEMENTS AND OTHER LESSONS LEARNT AT THE INTERNATIONAL LEVEL

In line with the experience from the dialogues, ICRP Publication 146 (dealing with radiologicalprotection of people and the environment in the event of a large nuclear accident) underlined theadded value of the co-expertise approach to assist the optimisation process and related decision
making. Co-expertise is defined as “an approach in which authorities, experts, and stakeholders
work together to share experience and information in affected communities, with the objective ofdeveloping a practical radiological protection culture to enable individuals to make informed decisions
about their own lives.” (ICRP, 2020)

4.2.4.

Activities and achievements of WANO

Following the accident at Fukushima Daiichi, WANO issued three Significant Operating Experience
Reports (SOERs) and one Addendum:• SOER 2011-2, Fukushima Daiichi Nuclear Station Fuel Damage Caused by Earthquake andTsunami, and SOER 2011-2 Addendum 1;• SOER 2011-3, Fukushima Daiichi Nuclear Station spent Fuel Pool/Pond Loss of Cooling and
Makeup;• SOER 2011-4, Near Term Actions to Address an Extended Loss of all AC Power.
Further to these, WANO published two revisions which together replaced the three SOERs listed
above:• SOER 2011-3 Rev. 1, Spent Fuel Facility Degradation, Loss of Cooling or Makeup;• SOER 2013-2 Rev. 1, Post-Fukushima Daiichi Nuclear Accident Lessons Learned.
WANO also identified a number of important changes to strengthen WANO and its focus on nuclear
safety, and it implemented all of them into its “business as usual” activities by October 2015. Added
to the scope of WANO activities were: i) emergency preparedness; ii) severe accident management;iii) on-site fuel storage; iv) some aspects of design as it relates to plant operation. As well, the following
areas were earmarked for development: i) implementing an integrated emergency response strategy;ii) improving visibility and transparency; iii) implementing a real-time event reporting process;iv) addressing equivalency of INPO, JANSI, IAEA and other peer reviews; v) conducting a corporate
review of every member within six years; vi) increasing peer review frequency to every four years;vii) adding an assessment or grading process; and viii) conducting an internal assessment of WANO
regional offices and headquarters.

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5. Global impact of lessons learntT

he Fukushima Daiichi accident has affected nuclear energy strategy in different countries andregions in different ways and to different extents. It also highlighted the strong importance ofhuman behaviour and organisational background for nuclear safety. The political, economic andsocial issues, including future energy supplies, global climate change, costs of alternatives andsecurity of energy supply, have varied across regions and countries. A few countries, such as Germany,
have made the decision to phase out their nuclear generating capacity. Elsewhere, low electricity
prices and the difficulty of financing new nuclear construction (especially after the global financial
crisis of 2008) have led to fewer new nuclear plant construction projects and some decisions to
reduce generating capacity or close older reactors in particular. Some countries have continued to
expand their nuclear generating capacity with the construction of new reactors and a growing list of“newcomer” countries are laying the groundwork to build new plants to meet future energy security
and environmental goals.

Workers heading to south of the Unit 2 reactor building of the Fukushima Daiichi Nuclear Power Plant
to install the adjoining platform. Source: TEPCO Holdings

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Renewed interest has been shown in alternative fuel designs that are more resistant to fuelfailure and hydrogen production. Several countries are conducting research and development onenhanced accident-tolerant fuels (ATFs; NEA, 2018b) and performing a lead test assembly or leadtest rod irradiation in commercial reactors. One particular research area of interest is focused on thedevelopment of cladding and core internal materials that can survive higher temperatures before
failure and that are less reactive with steam (thereby reducing the production of hydrogen such as was
generated during the Fukushima Daiichi accident).
The accident has also contributed to the massive global surge in recent years in the developmentof new nuclear power technologies, including small modular reactors and Generation IV reactors with
passive safety features. With about 70 development projects underway in countries around the world,
industry intends that these new technologies will address public concerns about safety and help
address the challenge of financing nuclear energy capacity.
In addition, many countries are placing more focus on fostering trust and confidence in their
nuclear policies by engaging stakeholders more completely in decision making. The Nuclear Energy
Agency (NEA) workshops on Stakeholder Involvement have been successful fora for exchanges ofexperiences and lessons learnt, and have benefited from the participation and perspectives of citizensof Fukushima Prefecture.
Over the past ten years, there has been tremendous improvement in the resilience of nuclear
plants; however, more in-depth activities remain to be done – particularly in human aspects of nuclear
safety. This chapter briefly reviews status and advancements in these areas.

5.1.

Lessons learnt on organisational factors and safety culture in NEA member
countries

5.1.1.

Enhancing the understanding of human aspects of nuclear safety

As observed in the NEA report Five Years After the Fukushima Daiichi Accident (NEA, 2016b), continuous
and innovative progress is fundamental to ensuring safety, even where many improvements have beenmade. Lessons learnt through operating experience and research will require continued attention.
This is particularly true for complex areas such as the human aspects of nuclear safety as reflected insafety culture, training and organisational factors. Constant vigilance and effort are needed at national
and international levels.
The NEA has supported activities and long-term initiatives on accident management, crisis
communications, precursor events, defence in depth (DiD), regulatory effectiveness, safety culture andregulation of new reactors. This has resulted in best practices and guidance for countries with existing,mature regulatory organisations and can be used for improving policies and practices, benchmarking aswell as training staff and ensuring knowledge and know-how transfer. Such activities are essential andfundamental in assisting countries to ensure the safe and effective deployment of nuclear technology.
Addressing the human aspects of nuclear safety, including organisational factors and safety
culture, is fundamental for the safe operation of nuclear installations as well as for the effectiveness ofregulatory authorities. These aspects also have an important impact on the potential future uses andregulation of nuclear technology. The NEA has continued to assist its member countries in their efforts
to enhance focus and improve the understanding and the technical basis for treating these elements.
NEA member countries continued to implement measures in the area of safety culture, reinforcing
their regulatory requirements and further developing their guidelines and guidance documents. They
also carried out various activities to ensure human and organisational factors are addressed which
have, for example, included the following:• The Radiation and Nuclear Safety Authority in Finland has begun implementation of risk-based
oversight of organisational factors. They are developing tools to look into the most important
issues of safety concerned with organisational factors.

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GLOBAL IMPACT OF LESSONS LEARNT• The Man-Technology-Organisation of the Institute for Energy Technology in Norway conducted astudy on Crew Decision Making with Degraded Information, to look at how human performanceis affected when information is missing or degraded, as this is relatively common and canincrease in severe situations or during cyber-attacks. This work focuses on the strategies
operators use to determine that the indications from their instruments are degraded, underwhat conditions they fail to notice degraded information, and how operators handle situations
with degraded information.

• Human factors are increasingly incorporated into many aspects of member countries’
approaches to nuclear safety.

5.1.2.

National culture and safety culture

Over the years, the importance of safety culture and its influence on nuclear safety has been
increasingly recognised. It has become increasingly evident that safety culture is influenced by manyfactors, among these factors are elements reflecting the national cultures. This question is not new,
but the Fukushima Daiichi accident brought it to the forefront and prompted a focussed responseto the issue (NEA, 2016h). Hence, it is important that the nuclear community take time to uncoverthese national influences, realise their potential impacts on safety and develop a path towards
sustaining a healthy safety culture. The Country-Specific Safety Culture Forum (CSSCF) is a step in thisdevelopment, conceived and implemented jointly by the NEA and the World Association of Nuclear
Operators (WANO) as a means of providing an arena to explore the impact of the national context on
nuclear safety and derive approaches to sustain and improve nuclear safety culture.
The concept behind the CSSCF is to start out from the respective country’s cultural realities
and conduct a reflective dialogue about strengths and weaknesses, as well as what can be done tostrengthen the safety culture within the authorities and operators concerned. In order to improvesafety culture, the attributes that make up the national context must be understood. It is important tokeep in mind that the national attributes are neither good nor bad. They can support a sound safety
culture or, if disregarded, can in some instances counteract safety culture. The goal of the CSSCF is not
to change the national attributes but rather to create awareness of how they manifest in organisational
behaviours and, potentially, highlight areas that mat be further addressed in training programmes. The
aim is to work within the national context for sustainable change.
The nuclear safety regulatory bodies of both Finland and Sweden have hosted CSSCFs (NEA,
2018e; NEA, 2019c) and all the organisations involved found them to have considerable benefit andto contribute towards enhancing the human and organisational factors of safety within a national
context. Canada and the United Kingdom are scheduled to host CSSCFs in the coming years. Both the
NEA and WANO are supportive of this approach and would recommend conducting CSSCFs in othermember countries – including those with established nuclear safety institutions and those wishing tofurther strengthen/develop their nuclear safety institutions.

5.1.3.

Defence and institutional strength in depth

Whereas rigorous and comprehensive safety standards and other tools may be in place, the Fukushima
Daiichi accident has clearly shown that to deliver high levels of safety the overall nuclear safety system
must ultimately ensure their diligent and effective application by the relevant institutions, taking
into account human and organisational factors. In other words, to achieve high levels of safety in all
circumstances and against all challenges, the nuclear safety system in its entirety must be robust.
Defence in depth (DiD) provides a systematic means to analyse and ensure layers of systems
to prevent or mitigate accidents. Activities to strengthen and further develop DiD are reported in
Implementation of Defence in Depth at Nuclear Power Plants (NEA, 2016a). The analogous concept ofstrength in depth (SiD), hinging on strong independent institutions, has been recognised as a powerfulaspect of accident prevention and management (IAEA, 2017).
There are three main independent organisational sub-systems in the overall nuclear safety system:a strong licensee, a strong and independent regulator, and a strong set of public stakeholders. Eachof these subsystems must possess the competence and capacity to fulfil its respective functions and
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duties. In addition, the subsystems should interact,encouraging and welcoming reciprocal questions
and challenges, and taking into consideration
others’ options and advice. Within each subsystem
there are multiple layers and components thatprovide the independence, diversity, redundancy
and separation of function required to prevent
single-point or common-cause failures. For example,
within the licensee subsystem, the individual
licensee is supported by peer layers at the national
and international level, and a further layer ofinternational institutions. Similarly, in the regulator
subsystem the regulatory authority is supported
by a layer of national and international technicalgroups, a layer of international peers, and a layer ofinternational institutions.

The refuelling floor on the upper part of the Unit 2 reactor
building at the Fukushima Daiichi Nuclear Power Plant.
Due to contamination by radioactive substances, thesituation is being stabilised using remote-controlled
heavy machinery and robots. Source: TEPCO Holdings

In summary, the application of institutional strength in depth as part of the human andorganisational approach to nuclear safety is a necessary building block to enhance and ensure nuclear
safety on a national and global basis.

5.2.

Accident, emergency and post-accident management: Resilience andbalancing decisions

5.2.1.

Resilience

A lesson reinforced by the Fukushima Daiichi Nuclear Power Plant accident is that it is necessary
to provide accident management measures for conditions more complex and/or more severe thanthose postulated for design basis accidents (DBAs). Additionally, the accident has highlighted the needto ensure accident management measures are robust and diverse so that they are not likely to becompletely defeated by a single event leading to a “cliff-edge” effect.
From this, the concept of strengthening resilience in emergency and accident management has
emerged. Resilience is having the ability within local, national and international plans to deal with
unprecedented events, and having the flexibility and agility to respond to the unexpected. This is anarea of considerable challenge when considering that accidents may require the operator and theregulatory body to face a large number of “unknown unknowns.” Resilience also requires the ability
to implement protection strategies that are effective, manageable and proportionate, and to have aplan for withdrawal of crisis-level intervention. Experience exists in non-nuclear areas and lessons
have been drawn from emergency management of hazards emanating from a variety of sectors (NEA,
2018a). Similar challenges are seen in non-nuclear events today with the national and international
responses to the COVID-19 pandemic.

5.2.2.

A holistic approach to optimisation

Balanced decision making to help achieve an optimised outcome in terms of nuclear safety andrisk has been fundamental to the operation and regulation of the nuclear industry. Optimisation
weighs a risk against the resources (effort, time and money) needed to control it. When dealing
with optimisation of protection, the ALARA principle is applied to ensure that doses all be kept “aslow as reasonably achievable”, taking into account economic and societal factors. Safety measures
are considered to be optimised if they provide a high level of safety across the industrial lifecycle
without unduly limiting the functional activities of the facilities using radiation. Thus, this processof optimising the risk in carrying out activities, actions and programmes describes the limit to whichsociety expects to see exposure controlled and the resources that society is willing to invest for control.

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GLOBAL IMPACT OF LESSONS LEARNTThe ALARA principle applies also to post-accident management, where additionally the costs andbenefits of countermeasures and the amount of waste created must be weighed. The accident at
Fukushima Daiichi, its immediate and longer-term aftermath, and the tasks of decommissioning thesite and dealing with the associated waste, have highlighted this point. Situations presenting potential
exposure to radiation are in general complex and require multidisciplinary attention, both during an
accident and in the post-accident management of the recovery. The experience has brought forward
the need to consider in a holistic way the wider environmental, societal, psychological, technologicaland economic costs and benefits of radiation applications and associated (potential) exposures,
but also, for recovery, of different options for protective action. Any given circumstance will haveparticular social, environmental, economic and political features that will influence the preferencesof stakeholders. Focusing resources on the reduction of one single risk, for example health risk fromradiation exposure, may lead to minimising exposure, but may not lead to well-balanced overall
protection of well-being. The global nuclear community undertakes to develop better understandingof these features and preferences extending far beyond the site perimeter and to address their fuller
integration into the process of balanced and optimised risk decision making.
The risks presented by the prevailing circumstances in the aftermath of the accident at Fukushima
Daiichi are, in general, very difficult to compare in qualitative terms. While it is possible to put amonetary value on the costs and consequences of controlling certain risks, a common framework isneeded in which significantly different aspects can be balanced to support risk-informed decisionmaking processes and determine the level of tolerability of risk and uncertainty.
Such complex decision making is inherently difficult, especially when outcomes affect a public
who may not have a direct part in decision making. It typically requires the establishment of aposition after taking multiple, sometimes contradictory factors into account, many characterised byuncertainty. Such positions and decisions are often required to be taken under time pressure andin confusing contexts where short-term emergent factors and long-term impacts cannot readily be
predicted. The decision to evacuate members of the public in response to the potential releases fromthe Fukushima Daiichi accident should be viewed in this context.
How to reach a consensus optimum decision in such circumstances is a challenge that must be
addressed, noting that international work can assist but each country must take into account differing
cultural backgrounds, and different social, economic and political environments. This again points tothe value of a more holistic and inclusive approach to decision making, considering a wider range offactors and inputs than radiological protection and nuclear safety decision routines may have usedin the past. Moreover, an agreed process needs to be put in place to determine the basis for endingor reversing a decision once its primary purpose has been achieved (or when assessment shows that
purpose cannot be fully achieved). This is a lesson re-emphasised by the difficulties encounteredby authorities and communities in seeking to return to their home places and reconstruct after the
temporary relocation decided at the time of the accident.

5.2.3.

Balancing risks of decisions in emergency situations

After the onset of the Fukushima Daiichi accident, multiple evacuation orders were declared over
several days, while decisions on voluntary evacuation took somewhat longer. The lessons learnt callfor reconsideration of implementing immediate evacuation because of the mortality risks associatedwith evacuations. Immediate evacuation was unsafe for patients from hospitals and nursing homes
and where preparation was insufficient led to higher mortality. These are also major lessons for
accident preparedness, where it seems appropriate to consider specific actions for vulnerable groups
such as elderly people to balance the risks of immediate evacuation against the possible benefitsof sheltering in place with continuous care (if ad hoc resources and care takers are available). Moregenerally, the Fukushima Daiichi accident experience suggests a need to better clarify and understandthe direct causes and risk factors for evacuation-related deaths. It has also shown that advice byknowledgeable experts must be carefully integrated in post-accident decisions, regarding both healthrisks from radiation exposure (helping individuals or communities answer the question “am I safe?”),and the potential deleterious effects of protective actions.
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As such, another crucial area relates to the mitigation of mental health and psycho-social impacts
on populations when implementing protective measures. The NEA contributed to the development of
the World Health Organization (WHO) framework on Mental Health and Psychosocial Support (MHPSS)in radiological or nuclear emergencies, adapting existing guidelines for non-nuclear emergency
settings (WHO, 2020). Recent NEA webinars helped to explore how the experience and lessons from
non-nuclear crises, such as the COVID-19 pandemic, could help countries to improve MHPSS in
the event of a nuclear or radiological emergency (NEA, 2020c). The NEA is furthermore developing
practical, feasible approaches to integrate MHPSS impacts in protective action decisions. The way
forward should include: i) developing methods for balancing direct health risks against the indirectconsequences of protective actions, by considering potential impacts on the most vulnerable groups(e.g., elderly, hospitalised population, etc.); ii) enabling more effective risk communication; iii) making
the best use of international good practice examples of MHPSS operations and adapting them to thenational/local plans and procedures; and iv) integrating logistical or other highly local aspects in
preparedness (e.g. effective access to health care and public services, relationship of the community orgroups to the natural environment and traditional areas).

6. Further challenges
stemming from the accidentJ

apan and many other countries have successfully addressed many issues and difficulties arisingfrom the accident and, importantly, identified and learnt lessons to make further improvements inglobal nuclear safety. The technical understanding of the accident is well established on the aspectsof its cause and how to prevent similar events. Many technical and regulatory issues have now been
resolved. However, scientific knowledge continues to evolve on how the accident progressed ineach unit, and on some aspects related to the accident consequences including those which are ofenvironmental, social, economic or political character. This chapter addresses ongoing and futurechallenges, noting their linkages. It revisits several aspects which have benefitted from discussion in
the preceding chapters.
Nuclear power is likely to play an important role in addressing the world’s energy future,
particularly as more countries take serious action to dramatically reduce emissions of carbon into
the atmosphere. Hence, ensuring that the lessons are embedded in future policies and practices isvital. This chapter also recalls the involvement of the international community, and the willingnessof the Nuclear Energy Agency (NEA) and its member countries to continue lending their support andexpertise.

6.1.

Technical challenges

6.1.1.

Fuel debris removal and associated forensic studies

The Japanese government, the Nuclear Damage Compensation and Decommissioning Facilitation
Corporation (NDF), the Tokyo Electric Power Company (TEPCO), the Japan Atomic Energy Agency (JAEA)
and other Japanese institutions continue to engage in significant work to determine how to remove
the fuel debris from the three stricken reactors on the Fukushima Daiichi site, and to prepare for thisunprecedented task. While the global scientific community is keen to learn from the effort, advancing
the decommissioning programme must remain the central priority.
The programme includes safety assessments, research and development and engineering studies,
as well as procurement of equipment, some of which represents novel, first-of-a-kind technology. The
fuel debris analysis has to be broad ranging. Its primary purpose will be to optimise the safety of thedecommissioning work and the safe treatment, storage, and eventual disposal of the fuel debris andassociated structures and materials. Also, the analysis will enhance scientific understanding of thephenomena affecting the fuel under accident conditions. Of particular interest are the location andform of the fuel debris and the extent to which knowledge of these can refine predictive modellingusing computer codes. Enhanced realism in such modelling provides a technical and simulation
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basis for improvements in technological plant-safety
responses, as well as in Severe Accident Management
Guidelines (SAMGs) and other procedures that can help
prevent and/or mitigate the evolution of any future
accident the world may encounter.
The NEA is well placed to support Japan and theinternational community in advancing this work.
The NEA can co-ordinate the interests of scientists
around the world to formulate a joint plan for forensic
investigation work on fuel debris in partnership withJapanese work, avoiding duplication and fosteringsynergies. Such collaboration and refinement werediscussed above in section 4.1.2.
Additionally, the NEA can assist Japan in its
development of the basis for fuel debris retrieval byco-ordinating the gathering of information from member
countries on important topics such as:

Fuel debris inside the primary containment vessel in
the Unit 2 reactor building at the Fukushima Daiichi
Nuclear Power Plant (fuel debris is a substance thathas cooled and re-solidified while being mixed withvarious materials after the fuel in the reactor melted
as a result of the accident). The image was captured
by a remote-controlled camera attached to the tip ofa survey device. Source: TEPCO Holdings• release of various radioactive materials related to fuel retrieval operations (e.g. radioactive dusts);• containment and ventilation systems for fine radioactive particles, especially alpha particles;• criticality assessment and protection under uncertain configurations and form of fissile
materials and moderators;• material (especially elastomers, plastics, greases and fluids) behaviours and properties in highly
radioactive environments;• use of robotics in highly radioactive environments.
This list is not exhaustive; there will be other advanced engineering challenges in the safe andeffective retrieval of fuel debris with which NEA and its members may be able to assist.

6.1.2.

Decontamination methods, environmental remediation and related waste issues

The decommissioning of Fukushima Daiichi will require the capability to decontaminate areas,
structures, equipment, etc., suitably and to create an inventory, condition, store and eventuallydispose of the contaminated and radioactive material. Both the safety of workers undertaking
decommissioning activities and the minimisation of radioactive waste are at stake (NEA,
forthcoming k). Because there are many methods of decontamination commercially available fromindustry, it would be useful to have a central data bank of such methods, their use, feasibility, cost andeffectiveness together with the science behind them. The NEA is already bringing together existingknowledge and information that can support ongoing decommissioning work and stimulate further
technological development to enable future tasks to be conducted more safely and efficiently.
Japan has undertaken a massive programme to decontaminate and remediate extensive
environmental areas affected by radioactive deposition from the accident. Some of these activities are
unprecedented considering the volumes and complexities involved, and additional work remains to
be done. Several NEA member countries have experience in such activities; assembling experts in thisfield to determine the state of the art, propose further scientific or other research, and draw lessons
would be advantageous. Other areas of the Organisation for Economic Co-operation and Development(OECD) also could provide useful input, given that there are economic and other considerations indetermining effective and efficient remediation.
Areas that could be considered include:• tools to compare various remediation/clean-up options (including the do-nothing or zero
option), assessment of options such as recycling of low-level contaminated materials (asconsidered in Japan), and identification of criteria to distinguish conventional waste from thatwhich needs special consideration as radioactive waste;

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FURTHER CHALLENGES STEMMING FROM THE ACCIDENT• guidance for a sustainable remediation approach, including those related to legislative andpolicy frameworks, taking into account the sustainability pillars (environmental, social andethical, and economic) and the impact of various end-state options;• information systems to compile, manage and store data and other knowledge used for decision
making and stakeholder engagement;• stakeholder involvement and strategies to maintain and build trust with the authorities at the
local and national levels in view of elaborating an environmental remediation plan, including
designing and siting final waste storage facilities.

6.1.3.

Solid waste management

Effective and efficient solid waste management
is at the core of safe economic and timely
decommissioning, and yet it remains oneof the most challenging areas for nuclear
programmes to demonstrate full lifecycle
stewardship to the public. Many countries
have struggled to establish disposal sites
for spent nuclear fuel and highly radioactive
waste and continue to face challenges in thescientific, engineering, societal and policy
domains. This is true also for Japan where
although studies on treatment and handling
methods are underway at present, final plans
for the disposal of radioactive waste fromthe decommissioning of Fukushima Daiichi
cannot yet be established.

Operators in the remote control room on the premises of
the Fukushima Daiichi Nuclear Power Plant. Remote control
technologies suitable for various working conditions have beendeveloped and are used where applicable. Source: TEPCO Holdings

Japan is currently engaging with the difficult waste management issues associated with large-scaledecommissioning posed by the Fukushima Daiichi site and surrounding area. The waste includes large
quantities of materials ranging from lightly contaminated soil, trees and other natural products, tothe very highly radioactive materials to be retrieved in future from inside the primary containment
vessel (PCV). NEA has publications across the range of issues (see section 4.1.3, and NEA, 2015b; 2016c;
2018d; forthcoming m), but more work is required to assist Japan and advance the basis worldwide toeffectuate closure of the nuclear fuel cycle. The NEA continues to gather experiences from around theworld on handling and disposing of complex radioactive waste, and the following areas are highlighted
for further development:

•
•
•
•

application of advanced technologies (e.g. robotics, digitalisation);
decommissioning cost evaluation practices (NEA, 2012f; 2014o; 2015l; 2017g; 2019i);
waste decisions and stakeholder engagement (see section 6.4);
strategy and approaches to the management of materials from decommissioning and territorial
rehabilitation;• multijurisdictional and multinational considerations for the safe storage, transport and disposalof waste;• management of information, data and knowledge.

6.2.

Regulation

A challenge of post-accident contexts such as Fukushima Daiichi is that their regulation cannot be
identical to that adopted for operating reactor sites or planned end-of-life decommissioning. The
Fukushima Daiichi site is in an uncertain state with many unknowns. Decommissioning of the nuclear
power plant is very complex and a flexible, stepwise process is being employed to gradually build up
knowledge and experience. The NEA has assisted by assembling regulatory experts from its member
countries to determine common lessons (NEA, 2019d).
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Japan’s Nuclear Regulation Authority (NRA) and other member country regulators would be served
by further insights into the following matters: regulation under uncertainty such as with special
decommissioning projects; optimisation decisions (see sections 5.2.2 and 6.5); effective regulatory
engagement with stakeholders and industry; and effective regulatory interactions with the licensees
and public.
The NRA has made tremendous progress in developing into a technically and independent nuclear
regulator over the last ten years. As is the case with many nuclear regulators, it has probably reacheda transition point where the opportunity exists to adapt to the fast-moving changes in society andfurther enhance its effectiveness through open and constructive dialogue with industry, on all levels.
The NRA has the basis for such evolution in its guiding principles that include “independent
decision making” and “openness and transparency.” In effecting these principles, the NRA has
implemented an external stakeholder engagement practice that includes a policy of strict distancing
from the nuclear industry. While recognising the significant difficulties in Japan stemming from theaccident at Fukushima Daiichi, it is important for regulators to strive, in keeping with the stated“characteristics of an effective regulator,” for balance and reasonableness in their approach todemonstrating independence and openness. As other NEA member countries can attest, such balance
can and should be achieved through multilateral and bilateral, public and non-public engagement
between the regulator and external stakeholders, including nuclear industry representatives; caremust be taken to conduct bilateral engagements with any stakeholder in a manner that avoids or
minimises the perception of bias or compromise. This approach balancing independence andopenness allows the regulator to avoid isolation, and to obtain the information needed to understandthe relevant issues and develop sound, timely regulatory decisions.
Broader stakeholder engagement can be an important process to reach consensus on optimum
decommissioning approaches for difficult activities or circumstances. Experience from NEA member
countries has shown that adopting innovative approaches to involving stakeholders in such decisions
can be of assistance. These processes can bring together regulators, government officials, local
public representatives, decommissioning strategic bodies (such as the NDF), and the site operators
to examine and agree on optimum decommissioning approaches. In situations where operators are
exposed to an increased short-term risk, parties to the meeting, such as the regulator, may choose
to favour a risk-informed approach over a prescriptive approach, so that reasonable actions can beundertaken that lead more directly to long-term hazard reduction.

6.3.

Rebuilding and revitalising communities and local economies

Japan is in the midst of rebuilding the areas damaged and evacuated following the tsunami and theaccident at Fukushima Daiichi, and revitalising that part of Japan. Among the excellent initiatives
taken by the operator are the effort by TEPCO’s FDEC to engage local business in the work at the site,
thereby building up their knowledge and expertise; and proposals to set up local scientific/technicalcentres of excellence focused on decommissioning needs for Fukushima Daiichi.
A public/private organisation, Fukushima Soso Reconstruction Corporation, was established by theJapanese government in 2015 to assist restarting affected businesses. The main points pursued by thejoint revitalisation team were to gain needed information locally, build trust with all economic actors,
co-operate with professionals for responding to the various issues, and reflect local needs in government
support measures. Although some businesses have restarted, there still remain many issues to be tackled,for example, business continuity or deep-rooted reputational damage caused by harmful rumours.
Revitalisation not only covers restarting business. Measures are also crucial for revitalisation offamily and social bonds, of cultural links, and of social, environmental and economic linkages between“sub-communities” (e.g. those created by the zoning actions after the disaster). Access to supportand services matching local needs must be reinforced. Ten years after the accident, food safety
management strongly interacts with economic aspects through consumers trust, the issue of loss ofimage for a region and/or a product, and/or how to secure the market for emblematic food products.
There is some understandable apprehension among citizens regarding residual levels of radioactive
contamination. Means have been provided in Japan for local citizens to exercise management inrelation to these concerns through monitoring programmes and advice on protective actions.

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These various issues must be embedded into a comprehensive and operational generic framework
enabling preparedness for post-accident recovery. This framework should provide guidance on how tomake the recovery decision-making process consensual, by involving a wide range of stakeholders who canbring local knowledge and expertise in order to achieve the best possible outcomes and provide insights on
how to build national and community resilience to minimise the societal disruption and facilitate recovery.
The NEA is in a unique position to assist with its close connection to the wider expertise in theOECD. The NEA can access specific country-based experience in rebuilding deprived areas, whether or
not these are characterised by widespread radioactive contamination and evacuation. Such synergistic
work could potentially assist Japan, and also benefit other countries confronted by the need to rebuild
local economies in a sustained and sustainable way. The NEA has already published several reports inthis area (NEA, 2014n; 2019g; forthcoming h). Such work has to take into account ethical considerations(see section 6.7) such as respecting the rights and autonomy of individuals.

Flower beds along the road in Tomioka Town (photo taken in June 2016). Source: Decontaminationarchive site, http://josen.env.go.jp/archive/detail/?TO-05-P0032

6.4.

Public and stakeholder engagement

Stakeholder trust in the institutions and decision makers who operate and oversee nuclear energy
programmes remains an ongoing issue in many NEA member states and was an overarching themeof the NEA’s 2017 and 2019 stakeholder involvement workshops (NEA, forthcoming i). Building longterm relationships, especially between individuals, with a range of stakeholders, including local
communities, is essential not only for navigating challenges but also for establishing the informed
confidence in the institutions which is integral to a democratic society. Trust is built upon openness,transparency, effective communication and meaningful engagement, which are intertwined,
resource-intensive, and often difficult to fully achieve. Nuclear-related communication is sometimes
viewed solely as translating scientific and technical language into accessible public messaging. In
fact, this is not the end goal, but instead the starting point for building meaningful, dialogue-based
relationships informed not only by science, but also by public needs and concerns. When stakeholders
experience their interactions and feedback being explicitly considered, being responded to openly
and transparently and influencing policies, it builds confidence, trust, and value in the nuclear energy
community, and increases robustness of policies.
At this tenth anniversary of the Fukushima Daiichi accident, next steps on the future of the site
will require operationalising these lessons by bringing together civil society stakeholders and those
across the Japanese government, regulatory bodies, industry, and regional entities in a co-ordinatedand transparent policy decision-making process. Communication, stakeholder relationships and trustat the international, national and local levels have impacted societal responses and resiliency in the
short and long term. Conscientious stakeholder relationships built on trust, openness, transparency,
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empathy, and communication offer pathways to policy decision making rooted in informed consent
and optimisation (see section 6.5) across the full range of impacts. NEA member countries recognisethat work in this area has broad applicability to the whole spectrum of nuclear policy and will continue
to support international co-operation advancing stakeholder engagement.

6.5.

Optimised holistic decision making

Experts in the radiological protection community and wider fora recognise that complex decision
making in a context like the one found at Fukushima Daiichi benefits greatly from a holistic approachto optimisation and decision making through wider information gathering and engagement. NEA
publications have reported the development of such an approach and offer guidance on how
to exchange information to make better informed decisions (NEA, 2012e; 2015a; forthcoming g;
forthcoming h). The role of a broadened range of stakeholders is actively discussed and experiences
are exchanged regarding means for their involvement. To take this further forward will require a wider
range of expertise that can involve other parts of the OECD.
Governments and regulators may also confront difficulties in establishing public support for policy
decisions on the disposal of radioactive waste, or on power station life extensions. Such decisions may
make sense based on scientific evidence, but may not be accepted socially or politically. Reaching a
consensus optimum policy decision in such circumstances is a challenge that must be addressed, notingthat international work can assist but each country must take into account differing cultural backgrounds
as well as different social, legal, economic and political environments. This again points to the need fora more holistic and inclusive approach to policy decision making, and for considering a wider range offactors and inputs than radiological protection and nuclear safety may have used in the past.
Optimisation is one of the three protection principles of the international radiological protection
system besides justification and limitation (as applicable). Briefly stated, doses should all be kept as
low as reasonably achievable (ALARA), taking into account economic and societal factors, and:• using an all-hazards approach – with optimisation of radiological exposure done by taking into
account other risks;• involving stakeholders where practical and appropriate – with stakeholder engagement being
integral to the policy decision-making process and key for defining acceptance or tolerance;• conducting structured analysis – proposing and comparing different options for protection, theircosts and their benefits;• referring to the need for proportionality – by implementing a graded approach.

Work on a tank that stores ALPS treated water generated on the premises of the Fukushima Daiichi
Nuclear Power Plant. Source: TEPCO Holdings

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There is a sense today that the approach to protection must evolve beyond the narrow optimisationof radiation exposure to place optimisation within the larger perspective of well-being. Methods andtools are needed to appropriately balance approaches to managing diverse risks, keeping in view
stakeholders’ needs and concerns, looking at the wider range of benefits beyond those to health,generating and assessing options on this basis. This will never be a one-size-fits-all approach; thehuman dimension is key and optimisation processes must integrate cultural and country-specificfeatures, as they are found at the time of application. Post-accident recovery can be improved bymaking the recovery process a bridge to a “new normal” designed according to the desired outcomesof the stakeholders. Such new processes should also embrace environmental optimisation.
The NEA is examining multidisciplinary practices for optimising health and safety within wider
environmental and socioeconomic contexts and under dynamic and uncertain conditions. However,more work is needed on how to achieve transparently accepted or tolerated and sustainable policy
decisions through a stakeholder-inclusive process of balancing the various risk components (coveringboth benefits and detriments) towards the identification of the best-balanced optimal protection.

6.6.

Institutional systems for ensuring nuclear safety

As the Japanese Diet independent report indicated (The National Diet of Japan, 2012), the Fukushima
Daiichi accident had as a root cause1 structural flaws in Japan’s nuclear administration – institutional
failure rather than technical failure. The failure of the system in place to ensure nuclear safety
furthermore led to a breakdown of public trust in the industry, regulator and government in Japan,
and raised concerns about other institutions elsewhere in the world. Understanding that the accident
was a system failure rather than attributable to just one or more components in the system is key toensuring that wider lessons are learnt. Looking at the technical aspects of the accident is necessary
but not sufficient if nuclear accidents with different direct causes are to be prevented.
Thus, rather than just reviewing or changing one component (such as the regulator) in the system
the whole nuclear safety system has to be considered, especially the interactions among components.
Some work has been undertaken in this area, for example the INSAG 27 report (IAEA, 2017), but moreis required to expand knowledge and understanding.

6.7.

Ethics for leaders and participants

One of the major issues stemming from the accident at the Fukushima Daiichi Nuclear Power Plant
was the loss of public trust. The accident demonstrated that trust is easily lost, and once lost very
difficult to rebuild. One of the major components of rebuilding trust is the regard that the public havefor what drives the professionals in a profession or organisation. Many leaders and professionals in
the nuclear industry, regulators and other organisations have a sense of purpose and working for thegreater good. This is reflected in professional bodies’ required standards of behaviours. WANO haspublished a document on nuclear leadership in which it is stated:
As leaders in the commercial nuclear industry, we carry a unique responsibility to upholdthe highest standards of nuclear safety while producing electricity reliably. Our ability toeffectively lead our organisations and teams is essential to fulfilling our obligations to all
key stakeholders: our employees, the public, regulators and our colleagues in the global
nuclear power community. (WANO, 2019, p. 2)
The International Commission for Radiological Protection (ICRP) has published Ethical Foundations of
the System of Radiological Protection (ICRP, 2018). The core ethical tenets are:• beneficence and non-maleficence (doing good and avoiding causing harm);• prudence (choosing carefully in cases where full knowledge is not available);1.
Accident investigators talk of direct causes and root causes. Direct causes (e.g. a tsunami) instigate the accident; root
causes are the underlying problems that would eventually surface in an accident or “near miss”.

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FURTHER CHALLENGES STEMMING FROM THE ACCIDENT• justice (being fair in sharing advantages and disadvantages);• dignity (respect to individuals – a human right).
These principles have foundations in the Hippocratic Oath that has been used to guide medical
physicians through the centuries, and which may be the basis for the general trust that the public hasin the medical profession.
Perhaps the time is ripe for the various strands of nuclear ethics, as indicated above, to be brought
together in an overarching code of ethics for nuclear leaders and professions worldwide. This could
be part of the basis of building sustained public trust and confidence in the peaceful use of nuclear
energy. The NEA with its member countries could be the catalyst for such an initiative. Such an ethicalcode could then lead onto principles for policy decision processes enhancing an open dialogue amongexperts, authorities and citizens.

6.8.

Intergenerational knowledge and experience

The hard-won experience and knowledge that comes from accidents such as that at the Fukushima
Daiichi site, and from the ensuing work to understand and implement lessons, must not be lost to
future generations. This is only one part of the nuclear knowledge and experience available. Variousorganisations and companies have their own knowledge management systems which in principle
must preserve both essential documents and tacit know-how and experience. The world needs amechanism of bringing all this together dynamically and making it accessible (respecting any security
and commercial considerations) across generations and countries. The NEA has initiated some workin this area (NEA, 2019d), and its Radioactive Waste Management Committee established the Working
Party on Information, Data and Knowledge Management in 2020.
It is noted that the NEA has a Data Bank service covering nuclear-related computer codes and data.
This may be able to act as a basis for a wider world knowledge management system building on a
Japanese system for knowledge management related to Fukushima Daiichi.

6.9.

A global system of international organisations working together

The response to the Fukushima Daiichi accident has benefited greatly from the closer working togetherof international organisations (see section 4.2). Looking into the future, such collaborative work will be
required as nuclear safety and radiological protection are continuously improved in an effective andefficient way as a basis for promoting nuclear power as a safe, robust, clean energy technology. Leadersof regulatory bodies meet periodically to learn from each other and address common issues, as doleaders of nuclear power companies to hold each other to account and promote excellence. Apartfrom some conferences, leaders of international organisations rarely get together to build mutually
beneficial collaborations. The relationships formed when jointly responding to the Fukushima Daiichi
accident could be used as a basis for further partnership to address other global issues including thoseof interest to other parts of the OECD.

6.10. Legal preparedness
The Fukushima Daiichi nuclear accident reminded the international community of the importanceof having a clear and comprehensive legal framework in place to enable the relevant bodies to react
quickly and adapt to the specific circumstances of the accident to ensure timely and financiallyadequate compensation to victims. Japan’s Act on Compensation for Nuclear Damage was an adequate
basis requiring only further supplement to adjust the legal framework to the context of the accident(see section 3.4.3 above).
The NEA has organised workshops to discuss the practical features of implementing a nuclear
liability regime, whether at the national or international levels, and consequences of the absence oftreaty relations. Such discussion should continue in order to support states with nuclear installations,and as many states as possible that may be affected by a nuclear accident, in adhering to one of thenuclear liability regimes and improving their national legislation as necessary.

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7. Conclusions and perspectivesT

he accident at Fukushima Daiichi was a seminal event for both the Japanese and global nuclear
sectors. Japanese governmental and industrial organisations have responded well to the accident,
especially in containing the accident’s effects and in being open and transparent with information.
Globally, the accident proved to be a watershed moment that spurred greater exchange of information
and best practices between nuclear regulators, the industry, and international organisations than had
been seen previously.
In Japan, improvements have been made to the regulation and oversight of nuclear technology.
A major focus is placed now on safely decommissioning the damaged reactors and remediating thesite in a manner that accommodates the needs and concerns of stakeholders at the local, national
and international level. The Fukushima Daiichi site entails unprecedented challenges – including
four heavily damaged reactors with three melted cores. The decommissioning effort is being pursued
with vigour in a structured manner with a focus on risk reduction and with a priority to ensure thesafety of workers, the public and the environment. A large earthquake struck Fukushima Prefecture
on 13 February 2021 and impacted the site. While analysis performed thus far indicates that this event
caused no significant difficulties at the Fukushima Daiichi site, it serves as a clear reminder of theneed to complete the decommissioning effort as soon as practical.
Off-site decontamination activities in the areas around the site have progressed well. Most
evacuation orders have been lifted and public services have been restored in many of the affectedareas. There is now a need to enhance the ongoing programme to rebuild and revitalise communities
and local economies. This is a significant challenge that is situated more largely in the realm ofcommunications and confidence-building than in that of radiological protection and nuclear safety.
Globally, lessons learnt have been applied to further enhance the safety of nuclear facilities,
particularly in ensuring the availability of robust and diverse systems to respond to accidents andextreme events. International experts, many of whom have been engaged with Japanese partners since
the early days of the accident to support Japan’s response to and recovery from the accident, seek
opportunities to enhance the world’s knowledge base. The shared learning and co-operation benefit
the global community, fuelling further progress in many areas of nuclear safety and radiologicalprotection – including stakeholder engagement.
Going forward, efforts in Japan and around the world continue to rebuild and enhance publictrust in nuclear operations. In this respect, new lessons continue to be learnt, such as enhancing
post-accident recovery by placing the human and societal dimension at the core of planning throughcomprehensive stakeholder involvement. It is now widely understood that earning public trust is a key
catalyst for recovery.
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CONCLUSIONS AND PERSPECTIVES

Decommissioning and management of radioactive wastes
The safe decommissioning of the site and surrounding areas and the careful management of wastes
associated with these activities are the clear priority for the effort in Japan to recover from the
Fukushima Daiichi accident. There is a need to develop a more comprehensive system to manage
the unconventional wastes emerging from the decommissioning effort, including the developmentof characterisation methods and techniques for legacy and unconventional waste, for effective
decommissioning and treatment, and for waste management. Fully engaging the global community
will tap into worldwide experience in addressing highly contaminated sites and highlight both goodpractices and methods to be avoided.
The decommissioning effort also calls for effective application of robotics and remote technologies.
This is another area ripe for international collaboration. Development at national and international
level of strategic approaches to facilitate the implementation of such advanced systems inradioactive waste management, decommissioning and legacy management will support the Japanese
decommissioning activities. In particular, there is a need for Japan and other countries to co-operate
in addressing the unique challenges associated with the use of remote tools to progress the removal offuel debris from the damaged reactors.

Nuclear safety and scientific knowledge
The technical understanding of the most significant aspects of the causes and progress of theaccident has advanced significantly, providing a firm basis for the measures undertaken to further
improve the safety of nuclear installations worldwide. In applying the lessons learnt, the specificsituation in a country (geography, regulatory framework, etc.) must be taken into account. While
the outcomes may be very similar, different priorities for enhancing safety and preventing andmitigating potential accidents are identified in each country. As the Fukushima Daiichi reactors
are decommissioned, there will be opportunities to gain further understanding of the specifics ofthe accident progression that can enhance the scientific knowledge base. For example, information
may be gained on core melt behaviour, fission products release, and the behaviour of nuclear power
plant components and structures, including spent fuel pools, in a severe accident. Japan can assume
a central role in the enhancement of safety and knowledge in some specific areas and Japanese
research capabilities could be augmented to take the best advantage of opportunities to gather new
scientific knowledge.
Worldwide operating experience combined with risk insights provides a source of potential
improvement or innovations, as demonstrated in the course of several events over the history of
global nuclear operations. The Fukushima Daiichi experience is adding significantly to this knowledge
base. There remain opportunities for learning associated with the evaluation and mitigation of thetechnical, environmental, social, political and economic consequences of the accident. One maintechnical challenge is related to the removal of debris, and fuel debris in particular. Accordingly, theanalysis of fuel debris must be broad-ranging, considering that its primary purpose will be to optimise
the safety of the decommissioning work and the safe treatment, storage, and eventual disposal of thefuel debris and associated structures and materials. There is considerable international interest in thiswork and many insights to be gained.

Stakeholder involvement and risk communication
Since the general public has great interest in the work underway to remediate the Fukushima Daiichi
site and surrounding areas, effective engagement with the citizens of Fukushima Prefecture is avery high priority. As has been observed in key fora in recent years, particularly the NEA Stakeholder
Involvement Workshops, relating complex technical topics to public stakeholders is a difficult taskthat requires considerable attention and resources. This is a challenge in Japan and in many othercountries.

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CONCLUSIONS AND PERSPECTIVESIn Japan, the Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF)
has made tremendous strides in developing effective public engagement. There is still a need in all
countries, including Japan, to find better approaches to giving stakeholders more opportunities tomake their views understood and to see them incorporated into the policy decision process.
The Fukushima Daiichi experience, over the last decade, has spurred considerable rethinking inJapan and in countries around the world as to how stakeholders should be involved in policy decision
making. The more traditional approach, in which governments, industry, and regulators decide upon acourse of action and simply inform stakeholders after the fact with limited public input, is giving way
to far more inclusive approaches.
It is now well accepted that involvement of stakeholders – including local authorities, industry,
nongovernmental organisations, government officials, and, of course, the general public – in policy
decision making is appropriate and advisable to enhance the credibility, legitimacy, sustainability, andfinal quality of decisions related to the recovery effort.
It is particularly important for there to be continued enhancement of stakeholder engagement byregulatory bodies. Japan’s nuclear safety regulator, the NRA, includes stakeholder engagement in its
guiding principles. The regulator can further build and enhance its effectiveness in addressing theconsequences of the Fukushima Daiichi accident through the conduct of an open and constructive
dialogue with industry, at all levels.
Analysis has led to the recognition that stakeholder engagement is essential also for off-site
emergency management planning decisions which have direct impact on the longer-term recovery
and quality of life in areas affected by the accident. As a result of these considerations, efforts in Japanand globally are needed to develop better means for communicating and discussing risk with thegeneral public, especially prior to any event. Such communication could potentially reduce the feelingsof uncertainty and fear that often arise during radiological events. A clear, straightforward approach isParticipants working on tasks at a workshop for female junior and senior high school students. The
students, mainly from the Fukushima Prefecture, are considering careers in science and engineering. The
event was attended by female scientists from Japan and overseas who participated as mentors, as part of a
joint project between Japan’s Nuclear Damage Compensation and Decommissioning Facilitation Corporation(NDF) and the NEA. Source: NDF

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CONCLUSIONS AND PERSPECTIVES

needed and new thinking is required to develop it. The United Nations Sendai Framework for disasterrisk reduction and promoting stakeholder involvement provides some insights to enhance community
engagement and societal resilience (UNISDR, 2015).
In addition to communicating risk, it is also important to ensure that risks are assessed in theirbroadest sense. In Japan and in all other countries, the international nuclear community mustenhance emergency preparedness, response and recovery after radiological events by taking into fullaccount and mitigating mental health and psychosocial impacts of protective decisions. Events suchas the Fukushima Daiichi accident may have serious long-term effects on people’s mental health andwell-being and these deserve as much consideration as potential radiation exposure. Overall, an allhazards approach for preparedness, response and recovery is recommended.
Addressing these matters will require direct engagement with the public in exchanges of views
and understanding. While this change in approach is challenging, it is necessary to achieve the needed
improvements.

Damage compensation
Also related to societal recovery from any radiological accident is assuring prompt compensation of
the affected population, which concerns the application and interpretation of the nuclear liability
regime and the practical logistical matters relating to the processing of the claims received. It is
crucial for all concerned parties (mainly the affected population, the liable operator and the insurers)
to know exactly what nuclear damage will be compensated for and how to estimate the allocatedcompensation. This could ensure that the affected population will be adequately compensatedwithout having to go before the courts, which is time consuming, stressful and costly. In addition, it isessential to have the foundations for an efficient claim handling process that would allow the affected
population wherever they are situated (on national territory or abroad) to start receiving compensation
immediately in the aftermath of a radiological event. The experience being gained in Japan in this area
will have global relevance.

Knowledge management
Internationally co-operative, integrated knowledge collection, management, and analysis of thelessons emerging from the Fukushima Daiichi accident have benefits for the efforts underway in Japanand for nuclear safety around the world. A vast amount of valuable knowledge has been gained thus
far and much more will be realised over the years to come. It is under the responsibility of Japan andof the international nuclear community to protect, share and make the most of this knowledge. It is
important that every opportunity be taken to assemble, preserve and manage this vital information
in a dynamic system accessible across generations and countries. This knowledge will facilitate theeffective conclusion of the remediation of the Fukushima Daiichi and the recovery of affected areas.
An integrative knowledge system will enhance severe accident management, waste management,
decommissioning, societal/community preparedness and post-accident recovery. It will contribute to
the improvement of nuclear operations around the world, and to the development of expertise in all
countries today and for future generations.

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8. Recommendations

T

he purpose of the Nuclear Energy Agency (NEA) is to support co-operation between countries
with advanced nuclear technology infrastructures to address challenges both existent and future.
The Agency and its membership have been very active in understanding, assessing, and responding
to the Fukushima Daiichi accident since it occurred a decade ago. The NEA will continue its focused
engagement with Japanese organisations to support this important member country in the years
to come as the recovery effort continues, as well as support its global membership in sharing andapplying the many lessons learnt from this experience.
The NEA’s ability to convene the finest experts from around the world, to quickly establish
co-operative frameworks between countries, and to disseminate lessons learnt has been and willcontinue to be applied to the unique and difficult challenges associated with recovery from the
Fukushima Daiichi accident.
In particular, the NEA may apply its resources – and those of relevant OECD programmes – toexplore many areas discussed in this report such as: the development of international co-operation
to pursue forensic investigation work on fuel debris in partnership with Japanese counterparts;
co-ordinating support to Japanese organisations in the development of the methods for the safe andeffective retrieval of fuel debris; bringing together the experience of member countries to support
efforts to manage and dispose of unconventional radioactive waste emerging from the accident andrecovery; and supporting efforts in Japan and globally to develop optimised approaches for emergency
response and decision making that fully involve stakeholders.
Over the last decade, Japan has demonstrated excellent co-operation with the NEA and othermember countries, just as many NEA members have demonstrated strong interest in engaging with
the Agency and Japan in relation to the accident. All have appreciated the openness and accessibility
shown by Japanese officials. It will be important for the NEA – as well as other internationalorganisations – to leverage the successful collaborations forged in the aftermath of the Fukushima
Daiichi accident to seek further, experience-based enhancements in global nuclear safety and tocontinue modernising radiological protection. These efforts will be essential as all pursue a common
goal of improving the lives of citizens across the world.
The concluding assessment that emerges from the analysis performed in the course of developing
this report is that Japanese authorities and organisations have risen very effectively to theunprecedented challenges presented by the Fukushima Daiichi accident and subsequent recovery. The
efforts to reduce risks at the site have been very successful and the way has been cleared for many
people to at least consider returning to their homes.
As Japanese authorities have stated consistently, there are still many years of hard work ahead. In
the course of writing this report, several areas for enhancement have been identified for consideration
by relevant Japanese organisations, supported by the NEA and other member countries, that mightenable improvements and efficiencies. This report concludes by highlighting these areas.
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RECOMMENDATIONS

Recommendation area 1: Regulatory environment
Japan’s regulatory environment was significantly reformed following the accident in 2011 to
specifically address issues of transparency, openness, and independence, with the creation of the NRA
in 2012. This has been a challenging transformation that has met with success in the implementationof plant improvements against natural phenomena such as tsunamis, and in safety improvements
aimed at station blackout threats to core cooling and backup electrical power – all specific lessons
learnt from the Fukushima experience. In accordance with NRA principles and a culture of continuous
improvement, the NRA could take opportunities to further enhance its open interaction with licensees
while maintaining its independence and integrity.

Recommendation area 2: Systematic approach to safety
Some international activities have undertaken to review the whole nuclear safety system, including
the interactions among the component organisations. This is an area on which all countries involvedin nuclear operations need to focus. However, additional effort could be given to expanding theknowledge and understanding of a systematic approach to safety, such as that provided by “defence
in depth” or “strength in depth”, to develop and institutionalise a system for nuclear safety thatprovides levels of protection and engages the industry, regulators and stakeholders. In adopting suchan approach, Japan would benefit from a holistic consideration of national objectives for stakeholder
involvement, ethics, and principles for intervention by all interested parties. Through this leadershipJapan could spur similar action in countries around the world.

Recommendation area 3: Decommissioning technologies
Relevant Japanese organisations could benefit from enhanced participation in international
collaborative efforts associated with areas such as: maintaining safety in difficult radiologicalenvironments; advanced robotics suitable for radioactive applications; the characterisation of complex
wastes; and technologies needed to support the extraction of core debris.

Recommendation area 4: Waste management and disposal
For the decommissioning of Fukushima Daiichi Nuclear Power Plant to be successful, the uniquewaste management challenges must be met. While there are welcome signs that this subject is being
addressed, the waste management challenges encountered in decommissioning Fukushima Daiichi
Nuclear Power Plant are unique and demanding. Areas for intensified focus include: identifying andsecuring disposal options for the wide variety of identified wastes and, in particular, the handlingof the treated water held on the site; continued research on characterisation of the unique andunconventional waste forms; and the safe and effective extraction, removal, stabilisation, and ultimate
disposal of fuel debris.

Recommendation area 5: Damage compensation
The Japanese government has worked to establish and implement the compensation scheme
necessary to respond to the Fukushima Daiichi nuclear accident. However, continuous improvement
efforts are needed to address the application and interpretation of the nuclear liability regime aswell as the practical logistical matters relating to the processing of the claims received. Such efforts
include the arrangement for concerned people being able to know exactly what nuclear damage will
be compensated for and how to calculate the allocated compensation; and implementation of an
efficient claims handling process to allow the affected population, wherever they are situated, to start
receiving compensation in a timely manner.

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Recommendation area 6: Stakeholder involvement and risk communication
A principal goal of the restructuring of the nuclear safety framework in Japan has been to repair
the damaged confidence of the public in the ability of institutions to communicate accurately risk
information to the public and the world, and to engage meaningfully the public in policy and decision
making that affects the public. This report has acknowledged several examples of notable progress inthis area. Stakeholder involvement and public engagement are extremely important in transitioning
to an environment of “informed consent” characterised by public participation and community
ownership in such policy decision making. Here, Japan has the opportunity to demonstrate global
leadership in this important aspect of the democratic implementation of nuclear energy policy.
Continued progress in developing means of informed public engagement leading to a unified
national effort to regulate and manage the nuclear energy sector is strongly encouraged. Specifically,
the openness, transparency, and engagement with the public by the institutions involved withdecommissioning the Fukushima Daiichi site, environmental remediation and revitalisation ofaffected territories, are commendable and strongly encouraged. In keeping with the principle of
optimisation, use of multi-stakeholder arrangements for risk-informed policy decisions on complex
hazard reduction decommissioning activities is encouraged.

Recommendation area 7: Recognition of mental health impacts
The recovery from the Fukushima Daiichi accident has involved not only the physical and healthsciences but also environmental, economic, social, philosophical/ethical and emotional considerations.
It is recommended that additional consideration be given to how to take into account the mental
health and well-being of the affected populations. Such considerations will contribute more broadly tocontinued improvement in nuclear or radiological accident preparedness and recovery management.
This is a global challenge in which Japan has a unique opportunity to assume a leadership role.

Recommendation area 8: Opportunities for economic redevelopment
The work on and around the Fukushima Daiichi site will proceed for many years and require newtechnologies and methodologies. This is both a challenge and an opportunity. As has been seen
in major radiological remediation activities around the world, this work could be embraced as anengine for creativity and economic growth. The need for new remote and robotic technologies forthe decommissioning work has already been identified a potential area of economic development.
The Japan Atomic Energy Agency’s Naraha Center for Remote Control Technology Development is
an excellent beginning. It may be possible to build on this success by incentivising global innovators
to come to Fukushima and develop robots for both nuclear and broader applications. Other, more
ambitious possibilities may exist. For example, examination of core debris, could draw academics
and researchers from around the world and serve as the core of a university-based research centre.
Authorities in Japan are encouraged to consider holding an international conference to highlightpossible paths to leverage the Fukushima Daiichi decommissioning work to the maximum benefit of
the people of the area.

Recommendation area 9: Knowledge management
The Fukushima Daiichi event which began on 11 March 2011 and persists to this day has been tragicand challenging to the people of Fukushima Prefecture, to the Japanese people and authorities, and to
the global community. While it has been a difficult experience with many more hurdles to be overcomein the future, it is also a source of learning and exploration. It is essential that a system to capture
lessons learnt from this event be established in order to secure the associated knowledge.
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RECOMMENDATIONS

While safe and timely decommissioningis the clear priority, it is also important toseize the opportunity to extract new lessons
that will contribute to nuclear safety and thedesign of future facilities – at the same time as
reinforcing the success of the decommissioning
operation. A clear opportunity lies in thescientific investigation of core debris materials
that will be removed in the course of thedecommissioning effort. Japan is uniquely
positioned to take a global lead in knowledge
management and invite interested partners
to contribute to these examinations and to
structuring their outcome.
More broadly, there are many aspects ofWorker analysing radioactivity concentration and water qualityof samples collected at and around the Fukushima Daiichi
the accident that can serve to enhance current
Nuclear Power Plant. A work support device called “smart
expertise and develop a new generation ofglasses” is worn to improve the productivity and quality of
specialists both in Japan and around the world.
data entry and confirmation. Source: TEPCO Holdings
This will benefit the global community wellinto the future and provide a strong incentive
for Japan’s international partners to remain engaged in the long-term decommissioning project.
Accordingly, Japanese organisations are encouraged to aggressively pursue national and internationalframeworks that will preserve, analyse, and disseminate the hard-won experience from the accident
at the Fukushima Daiichi Nuclear Power Plant.

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References and further readingT

he following includes both the documents cited in this report, and an extensive but notexhaustive list of pertinent documents by the Nuclear Energy Agency (NEA) and other Japanese orinternational bodies. The NEA 2019 Annual Report (NEA, 2020a) covers all aspects of the Agency’s workand provides details of the many working parties and expert groups addressing topics of interest.
Callen J. and T. Homma (2017), “Lessons Learned in Protection of the Public for the Accident at the
Fukushima Daiichi Nuclear Power Plant”, Health Physics: The Radiation Safety Journal, Vol. 112 (6),pp. 550-559, Wolters Kluwer Health, Inc.. DOI: 10.1097/HP.0000000000000666.
ENSREG (2013), Report of the European Nuclear Safety Regulator’s Group, HLG_p (201324)117, European Nuclear Safety Regulators Group. www.ensreg.eu/document/
third-report-european-nuclear-safety-regulators-group-july-2013
IAEA (2006), Fundamental Safety Principles, IAEA Safety Standards Series No. SF-1, International Atomic
Energy Agency, Vienna. www-pub.iaea.org/MTCD/Publications/PDF/Pub1273_web.pdf
IAEA (2011), Draft IAEA Action Plan on Nuclear Safety, Report by the Director General,
GOV/2011/59-GC(55)/14, International Atomic Energy Agency, Vienna. www.iaea.org/sites/default/
files/gc/gc55-14_en.pdf
IAEA (2013), The Follow-up IAEA International Mission on Remediation of Large Contaminated Areas Offsite the Fukushima Daiichi Nuclear Power Plant, Preliminary Summary Report, Tokyo and Fukushima
Prefecture, Japan, 14-21 October 2013, International Atomic Energy Agency, Vienna. www.iaea.org/
sites/default/files/preliminarysummaryreport.pdf
IAEA (2014a), IAEA International Peer Review Mission on Mid-and-Long-Term Roadmap Towards theDecommissioning of TEPCO’s Fukushima Daiichi Nuclear Power Station Units 1-4, Mission Report, Second
Mission, Tokyo and Fukushima Prefecture, Japan, 25 November – 4 December 2013, International
Atomic Energy Agency, Vienna. www.iaea.org/sites/default/files/IAEAfinal_report120214.pdf
IAEA (2014b), 6th Review Meeting of the Contracting Parties to the Convention on Nuclear Safety Summary
Report, 24 March-4 April 2014, CNS/6RM/2014/11_Final, International Atomic Energy Agency, Vienna.
www.iaea.org/sites/default/files/2014-cns-summary-report-w-annexes-signed.pdf
IAEA (2015), The Fukushima Daiichi Accident, Report by the Director General, STI/PUB/1710, International
Atomic Energy Agency, Vienna. www.iaea.org/publications/10962/the-fukushima-daiichi-accident
IAEA (2017), Ensuring Robust National Nuclear Safety Systems – Institutional Strength in Depth, INSAG-27,
A report by the International Nuclear Safety Group, International Atomic Energy Agency, Vienna.
www-pub.iaea.org/MTCD/Publications/PDF/P1779_web.pdf
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REFERENCES AND FURTHER READING

IAEA (2019), IAEA International Peer Review Mission on Mid-and-Long-Term Roadmap towards theDecommissioning of TEPCO’s Fukushima Daiichi Nuclear Power Station, Mission Report, Fourth Mission,
Tokyo and Fukushima Daiichi NPS, Japan, 5-13 November 2018, International Atomic Energy Agency,
Vienna. www.iaea.org/sites/default/files/19/01/missionreport-310119.pdf
IAEA (2020), IAEA Follow-up Review of Progress Made on Management of ALPS Treated Water and the Report of
the Subcommittee on Handling of ALPS treated water at TEPCO’s Fukushima Daiichi Nuclear Power Station,
Review Report, International Atomic Energy Agency, Vienna. www.iaea.org/sites/default/files/20/04/
review-report-020420.pdf
ICRP (2016), “Increase in Disaster-Related Deaths: Risks and Social Impacts of Evacuation”, Report by
A.M. Hayakawa, Annals of the ICRP, Dec; 45(2_suppl), pp. 123-128, International Commission on
Radiological Protection, Sage, London. DOI: 10.1177/0146645316666707.
ICRP (2018), “Ethical Foundations of the System of Radiological Protection”, Annals of the ICRP; 47(1),pp. 1-65, ICRP Publication 138, International Commission on Radiological Protection, Sage, London.
DOI: 10.1177/0146645317746010
ICRP (2020), “Radiological Protection of People and the Environment in the Event of a Large Nuclear
Accident”, Annals of the ICRP; 49(4), pp. 11-135, ICRP Publication 146, International Commission on
Radiological Protection, Sage, London. DOI: 10.1177/0146645320952659.
The Investigation Committee on the Accident at Fukushima Nuclear Power Stations of Tokyo ElectricPower Company (2011), Interim Report by the Government Investigation Committee on the Accident at
Fukushima Nuclear Power Stations of Tokyo Electric Power Company, Tokyo. www.cas.go.jp/jp/seisaku/
icanps/eng/
The Investigation Committee on the Accident at Fukushima Nuclear Power Stations of Tokyo ElectricPower Company (2012), Final Report by the Government Investigation Committee on the Accident at
Fukushima Nuclear Power Stations of Tokyo Electric Power Company, Tokyo. www.cas.go.jp/jp/seisaku/
icanps/eng/
MAFF (2020), Summary of Monitoring on Fishery Products, Fisheries Agency of Japan, Ministry ofAgriculture, Forestry and Fisheries, Tokyo. www.jfa.maff.go.jp/e/inspection/index.html
METI (2011), Mid-and-Long-Term Roadmap towards the Decommissioning of Fukushima Daiichi Nuclear Power
Station Units 1-4, TEPCO, Nuclear Emergency Response Headquarters Government and TEPCO’s Midto-Long Term Countermeasure Meeting, Ministry of Economy, Trade and Industry, Tokyo. www.meti.
go.jp/english/earthquake/nuclear/decommissioning/pdf/111221_02.pdf
METI (2019), Mid-and-Long-Term Roadmap towards the Decommissioning of TEPCO’s Fukushima Daiichi
Nuclear Power Station (The 5th Revision), The Inter-Ministerial Council for Contaminated Water andDecommissioning Issues, Ministry of Economy, Trade and Industry, Tokyo. www.meti.go.jp/english/
earthquake/nuclear/decommissioning/pdf/20191227_3.pdf
METI (2020a), The Subcommittee on Handling of the ALPS Treated Water Report, The Subcommittee on
Handling of the ALPS Treated Water, Ministry of Economy, Trade and Industry, Tokyo. www.meti.
go.jp/english/earthquake/nuclear/decommissioning/pdf/20200210_alps.pdf
METI (2020b), Outline of Decommissioning and Contaminated Water Management (Progress Status Report,
September 2020), Secretariat of the Team for Countermeasures for Decommissioning andContaminated Water Treatment, Ministry of Economy, Trade and Industry, Tokyo. www.meti.go.jp/
english/earthquake/nuclear/decommissioning/progress_status.html
The National Diet of Japan (2012), The Official Report of the Fukushima Nuclear Accident Independent
Investigation Commission Executive Summary, The National Diet of Japan, Tokyo, Japan. https://warp.
da.ndl.go.jp/info:ndljp/pid/3856371/naiic.go.jp/en/report
NDF (2020), Technical Strategic Plan 2020 for the Decommissioning of the Fukushima Daiichi Nuclear Power
Station of Tokyo Electric Power Company Holdings, Inc. (2020 revision), Nuclear Damage Compensation
and Decommissioning Facilitation Corporation, Tokyo. www.dd.ndf.go.jp/en/strategic-plan/
book/20201214_SP2020eFT.pdf

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REFERENCES AND FURTHER READINGNEA (2000), “Impact of Short-Term Severe Accident Management Actions in a Long-Term Perspective”,
NEA/CSNI/R(2000)8, OECD Publishing, Paris. www.oecd-nea.org/upload/docs/application/pdf/202001/csni-r2000-8.pdf
NEA (2011a), Practices and Experience in Stakeholder Involvement for Post-nuclear Emergency Management,
NEA Publication No. 6994, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_14694/
practices-and-experience-in-stakeholder-involvement-for-post-nuclear-emergency-management
NEA (2011b), “Status of National Actions in Response to the TEPCO Fukushima Daiichi Accident_
Technical Note”, NEA/SEN/NRA/WGOE(2012)1, OECD Publishing, Paris. www.oecd-nea.org/jcms/
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NEA (2011c), “NEA Forum on the Fukushima Accident: Insight and Approaches – Forum Proceedings,
Paris, France, 8 June 2011”, NEA/CNRA/R(2011)12, OECD Publishing, Paris. www.oecd-nea.org/jcms/
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NEA (2011d), Nuclear Law Bulletin No. 88. NEA Publication No. 7001, OECD Publishing, Paris. www.oecdnea.org/jcms/pl_14706/nuclear-law-bulletin-no-88-volume-2011/2
NEA (2012a), OECD Nuclear Energy Agency (NEA) Activities in Follow-Up to the TEPCO Fukushima Daiichi Nuclear
Accident (2012), NEA Publication No. 6888, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_14564/
oecd-nuclear-energy-agency-nea-follow-up-to-the-tepco-fukushima-daiichi-nuclear-accident
NEA (2012b), The Economics of Long-term Operation of Nuclear Power Plants, NEA
Publication No. 7054, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_14752/
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NEA (2012c), Japan’s Compensation System for Nuclear Damage, NEA Publication No. 7089, OECD, Paris.
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NEA (2012d), “Challenges in Long-Term Operation of Nuclear Power Plants - Implications forRegulatory Bodies”, NEA/CNRA/R(2012)5, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_19170/
challenges-in-long-term-operation-of-nuclear-power-plants-implications-for-regulatory-bodies
NEA (2012e), “Patterns in Governmental Decisions and Recommendations (GDR) Information Exchange
During the Fukushima NPP Accident”, NEA/CRPPH(2012)3, OECD Publishing, Paris. www.oecd-nea.
org/jcms/pl_19152/patterns-in-governmental-decisions-and-recommendations-gdr-informationexchange-during-the-fukushima-npp-accident
NEA (2012f), International Structure for Decommissioning Costing (ISDC) of Nuclear Installations,
NEA Publication No. 7088, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_14804/international-structure-for-decommissioning-costing-isdc-of-nuclear-installations
NEA (2013a), Stakeholder Confidence in Radioactive Waste Management An Annotated Glossary of Key Terms,
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NEA (2013b), Crisis Communication: Facing the Challenges, NEA Publication No. 7067, OECD Publishing,Paris. www.oecd-nea.org/jcms/pl_14774/crisis-communication-facing-the-challenges-proceedings
NEA (2013c), Transition Towards a Sustainable Nuclear Fuel Cycle, NEA Publication No. 7133, OECD Publishing,Paris. www.oecd-nea.org/jcms/pl_14844/transition-towards-a-sustainable-nuclear-fuel-cycle
NEA (2013d), The Fukushima Daiichi Nuclear Power Plant Accident: OECD/NEA Nuclear Safety
Response and Lessons Learnt, NEA Publication No. 7161, OECD Publishing, Paris. www.
oecd-nea.org/jcms/pl_14866/the-fukushima-daiichi-nuclear-power-plant-accident-oecd/
nea-nuclear-safety-response-and-lessons-learnt
NEA (2014a), The Characteristics of an Effective Nuclear Regulator, NEA Publication No. 7185, OECD Publishing,Paris. www.oecd-nea.org/jcms/pl_14892/the-characteristics-of-an-effective-nuclear-regulator
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REFERENCES AND FURTHER READINGNEA (2014b), “Probabilistic Safety Assessment (PSA) of Natural External Hazards
Including Earthquakes, Workshop Proceedings”, Prague, Czech Republic, 17-20 June
2013, NEA/CSNI/R(2014)9, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_19518/
psa-of-natural-external-hazards-including-earthquakeworkshop-proceedings
NEA (2014c), “Status Report on Hydrogen Management and Related Computer Codes”,
N E A / CSNI /R ( 2 0 1 4 ) 8 , O E C D P u bl i s h in g, Paris. w w w.oec d-n ea.org/ jc ms/ pl_19516/
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NEA (2014d), “Status Report on Filtered Containment Venting”, NEA/CSNI/R(2014)7, OECD Publishing,Paris. www.oecd-nea.org/jcms/pl_19514/oecd/nea/csni-status-report-on-filtered-containmentventing
NEA (2014e), “WGOE Report on Fukushima Daiichi NPP Precursor Events”, NEA/C N R A / R ( 2 0 1 4 ) 1 , O E C D P u b l i s h i n g , P a r i s . w w w. o e c d - n e a . o r g / j c m s / p l _ 1 9 3 9 5 /wgoe-report-on-fukushima-daiichi-npp-precursor-events
NEA (2014f), “12th Workshop on Experience from the Inspection of Licensee’s Outage Activities
Including Fire Protection Programmes, Event Response Inspections, and the Impact on Inspection
Programmes of the Fukushima Daiichi NPP Accident – Workshop Proceedings”, Chattanooga,
Tennessee, USA, 7-10 April 2014, NEA/CNRA/R(2014)8, OECD Publishing, Paris. www.oecd-nea.org/
jcms/pl_19558/12th-workshop-on-experience-from-the-inspection-of-licensee-s-outage-activitiesincluding-fire-protection-programmes-event-response-inspections-and-the-impact-on-inspectionprogrammes-of-the-fukushima-daiichi-npp-accident-workshop-proceedings-chattanoogatennessee-usa-7-10-april-2014
NEA (2014g), “Report of the Survey on the Design Review of New Reactor Applications – Instrumentation
and Control”, NEA/CNRA/R(2014)7, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_19538/reporton-the-survey-of-the-design-review-of-new-reactor-applications-volume-1-instrumentation-andcontrolvolume-1instrumentation-and-control
NEA (2014h), “Supplementary Report on the Regulation of Site Selection and Preparation: CNRA Working
Group on the Regulation of New Reactors”, NEA/CNRA/R(2014)5, OECD Publishing, Paris. www.oecdnea.org/jcms/pl_19524/supplementary-report-on-the-regulation-of-site-selection-and-preparation
NEA (2014i), “NEA/CNRA/CSNI Joint Workshop on Challenges and Enhancements to Defence in Depth(DiD) in Light of the Fukushima Daiichi NPP Accident: Workshop Proceedings”, NEA/CNRA/R(2014)4,
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NEA (2014j), “Accident Management Insights After the Fukushima Daiichi NPP Accident: Report of the
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NEA (2014m), “Occupational Radiation Protection in Severe Accident Management”,
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NEA (2014o), Guide for International Peer Reviews of Decommissioning Cost Studies for Nuclear Facilities,
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REFERENCES AND FURTHER READINGNEA (2015a), Stakeholder Involvement in Decision Making: A Short Guide to Issues, Approaches and Resources,
NEA Publication No. 7189, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_14894
NEA (2015b), Fostering a Durable Relationship Between a Waste Management Facility and its Host Community
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NEA (2015d), “Human Performance under Extreme Conditions with Respect to a Resilient Organisation:
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NEA (2015e), “Robustness of Electrical Systems of Nuclear Power Plants in Light of the Fukushima
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NEA (2015g), “Report of the Survey on the Design Review of New Reactor Applications, Volume 2: Civil
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REFERENCES AND FURTHER READINGNEA (2016f), “State-of-the-Art Report on Molten-Corium-Concrete interaction and Ex-Vessel MoltenCore Coolability”, NEA/CSNI/R(2016)15, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_19746
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NEA (2018b), State-of-the-Art Report on Light Water Reactor Accident-Tolerant Fuels, NEA Publication
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NEA (2018c), Experience from the Fifth International Nuclear Emergency Exercise (INEX-5), NEA Publication
No. 7379, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_15064
NEA (2019d), Challenges in Nuclear and Radiological Legacy Site Management – Towards a Common Regulatory
Framework, NEA Publication No. 7419, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_40359/
challenges-in-nuclear-and-radiological-legacy-site-management-towards-a-common-regulatoryframework
NEA (2018e), Country-Specific Safety Culture Forum: Sweden, NEA Publication No. 7420, OECD Publishing,Paris. www.oecd-nea.org/jcms/pl_15086
NEA (2018f), Executive Summary of Towards an All-Hazards Approach to Emergency Preparedness andResponse, NEA Publication No. 7436, OECD Publishing, Paris. www.oecd-nea.org/rp/pubs/2018/7436all-hazards-epr-es.pdf
NEA (2018g), Proceedings of the Fifth International Nuclear Emergency Exercise (INEX-5) Workshop, NEA
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REFERENCES AND FURTHER READINGNEA (2018h), “Developments in Fuel Cycle Facilities after the Fukushima Daiichi Nuclear Power Station
Accident”, Workshop Proceedings Aomori City, Japan 15-17 November 2016, Appendix 3, NEA/CSNI/R(2017)12/ADD1, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_19840/developmentsin-fuel-cycle-facilities-fcfs-after-the-fukushima-daiichi-nuclear-power-station-nps-accidentworkshop-proceedings-appendix-3
NEA (2018i), “Examination of Approaches for Screening External Hazards”, NEA/CSNI/R(2018)7, OECD
Publishing, Paris. www.oecd-nea.org/jcms/pl_19860
NEA (2019a), Occupational Exposures at Nuclear Power Plants (2016), Twenty-Sixth Annual Report of the
ISOE Programme, 2016, NEA Publication No. 7453, OECD Publishing, Paris. www.oecd-nea.org/jcms/
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NEA (2019b), Insights from Leaders in Nuclear Energy: Safety, Performance and Responsibility,
NEA Publication No. 7461, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_15134/
insights-from-leaders-in-nuclear-energy-safety-performance-and-responsibility
NEA (2019c), Country Specific Safety Culture Forum – Finland, NEA Publication No. 7488, OECD Publishing,Paris. www.oecd-nea.org/jcms/pl_15146
NEA (2019d), NEA International Mentoring Workshop in Fukushima, August 2019, NEA
Publication No. 7514, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_28696/
mentoring-a-future-generation-of-female-leaders-in-science-and-engineering-2019
NEA (2019e), “Riverine Flooding: Hazard Assessment and Protection of Nuclear Installations”,
NEA/CSNI/R(2018)14, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_37980/
riverine-flooding-hazard-assessment-and-protection-of-nuclear-installations
NEA (2019f), “Components and Structures under Severe Accident Loading (COSSAL)”, NEA/CSNI/R(2019)2, OECD, Paris. www.oecd-nea.org/jcms/pl_19898
NEA (2019g), “Summary Report of the Joint Symposium on Decommissioning, Reconstruction,
Rehabilitation, and Food Safety: Rebuilding Post-Accident Confidence”, Paris, France, 26 March 2019,
NEA/CRPPH/R(2019)5, OECD, Paris. www.oecd.org/officialdocuments/publicdisplaydocumentpdf/?cote=NEA/CRPPH/R(2019)5&docLanguage=En
NEA (2019h), Summary of the NEA Workshop on the Application of Remote and Robotic Systems in Nuclear
Back-End Activities – Way Forward in System Implementation, OECD Publishing, Paris. www.oecd-nea.
org/rwm/workshops/2019/robsysnba/docs/summary.pdf
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Publication No. 7460, OECD Publishing, Paris. www.oecd-nea.org/jcms/pl_15132/
cost-benchmarking-for-nuclear-power-plant-decommissioning
NEA (2020a), Annual Report 2019, NEA Publication No. 7517, OECD Publishing, Paris. www.oecd-nea.org/
jcms/pl_28563
NEA (2020b), Occupational Exposures at Nuclear Power Plants (2017), Twenty-Seventh Annual Report of the
ISOE Programme, 2017, NEA Publication No. 7510, OECD Publishing, Paris. www.oecd-nea.org/rp/
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NEA (2020c), Lessons learnt from non-nuclear crises: Making the most of practical experiences gained during
past crises or disasters for improving mental health and psychosocial support in radiation emergencies, OECD
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NEA (forthcoming a), Methods for Assessing and Strengthening the Safety Culture of the Regulatory Body,
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NEA (forthcoming b), Long-Term Management and Actions for a Severe Accident in a Nuclear Power Plant,OECD Publishing, Paris.
NEA (forthcoming c), “Status of Site-level (Including Multi-Units) PSA Developments”, NEA/CSNI/R(2019)16, OECD Publishing, Paris.
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REFERENCES AND FURTHER READINGNEA (forthcoming d), Concepts and Terminology for Protecting Nuclear Installations from Flood Hazards, OECD
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NEA (forthcoming e), Advancing the Robustness of Electrical Power Systems of Nuclear Power Plants, OECD
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NEA (forthcoming f), “CSNI WGAMA Source Term Workshop 2019”, OECD Publishing, Paris.
NEA (forthcoming g), “Workshop Summary Report NEA Workshop on Optimisation: Rethinking the Art
of Reasonable”, Lisbon, Portugal, 13-15 January 2020, OECD Publishing, Paris.
NEA (forthcoming h), “Workshop Summary Report NEA Workshop on “Preparedness for Post-Accident
Recovery: Lessons from Experience” co-organised with the Japanese Nuclear Regulation Authority,
Tokyo, Japan, 18-19 February 2020, OECD Publishing, Paris.
NEA (forthcoming i), Towards a Shared Understanding of Radiological Risks: Summary Report of the NEA
Stakeholder Involvement Workshop on Risk Communication, Paris, France, 24-26 September 2019, OECD
Publishing, Paris.
NEA (forthcoming j), Thermodynamic Characterisation of Fuel Debris and Fission Products Based on Scenario
Analysis of Severe Accident Progression at Fukushima Daiichi Nuclear Power Station (TCOFF) Project
Summary Report, OECD Publishing, Paris.
NEA (forthcoming k), Characterisation Methodology for Unconventional and Legacy Waste, OECD Publishing,Paris.
NEA (forthcoming l), “Dialogue in the Long-term Management of Radioactive Waste”, NEA/
RWM/R(2020)1, OECD Publishing, Paris.
NEA (forthcoming m), Fourth International Workshop on the Indemnification of Damage in the Event of a
Nuclear Accident, Lisbon, Portugal, 8-10 October 2019, OECD Publishing, Paris.
NEA (forthcoming n), BSAF-2 Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Plant
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REFERENCES AND FURTHER READINGUS Department of Energy (2019), Amway, P., Andrews, N., Basu, S., Bunt, R., Butler, J., Ellison, P.,
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COVER PHOTO DESCRIPTION

The photo on the cover, taken in April 2019, is of a street planted with cherry trees in the
Yonomori district of Tomioka Town. The location is a little over 7 kilometres from the
Fukushima Daiichi Nuclear Power Plant. Although access to this area was restricted for a longtime after the accident, residents were allowed to visit during the cherry blossom season,
when they enjoyed the same full-bloomed cherry blossom scene as before the accident.
On 10 March 2020 the government lifted evacuation orders for a total of about 1.1 kilometres ofroad around Yonomori Station on the JR Joban Line and railway facilities in a difficult-to-returnarea of Tomioka Town. This release area, which is adjacent to the street shown in the photothat was also released back in 2017, made the cherry blossom corridor in total 1 kilometre
long. The total area released was about seven hectares, but it is limited to the area around theroad and railway station building. The aim is for residents to be able to make a full return inthe spring of 2023.
In February 2021 Tomioka Town was carrying out environmental rehabilitation work with thegovernment’s aid. The project included dismantling deteriorated buildings, restoring roads andreconnecting water and sewage in an area of about 390 hectares in the difficult-to-return areaby the spring of 2023. This planned area, a “Specified Reconstruction and Revitalization Base”
will ultimately accommodate approximately 1 600 people in 2028.

表紙写真の説明
表紙の写真は2019年4月に撮影された、富岡町夜の森地区の桜並木です。
この場所は福島第一原
子力発電所から7キロ強です。事故後長期間にわたってこのエリアへの立ち入りは制限されていましたが、住民は桜の開花の季節に訪れることが可能となり、事故前と変わらない満開の桜のシーンを楽しんでいます。
2020年3月10日、政府は、富岡町における帰還困難区域のうちJR常磐線の夜ノ森駅周辺の合計約
1.1キロメートルの道路と鉄道施設の避難命令を解除しました。2017年に避難指示が解除された
写真の通りと今回の解除エリアとがつながり、約１キロメートルもの桜並木が形成されました。解除された面積は合計約7ヘクタールでしたが、道路や駅舎周辺に限られており、住民が2023年春に帰還できるようにすることを目指しています。
2021年2月現在、富岡町は政府の支援を受けて環境修復工事を実施しています。
このプロジェクト
には、2023年春までに帰還困難区域の約390ヘクタールの地域で、劣化した建物の解体、道路及び上下水道の復旧を行う工事が含まれています。
この計画地域は、「特定復興再生拠点区域」と呼ばれており、2028年に約1600人が居住することを目標としています。

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Fukushima Daiichi Nuclear Power Plant
Accident, Ten Years On: Progress, Lessons
and Challenges
Much has been learnt in the ten years since the Great Eastern Japan Earthquake and the subsequent
accident at the Fukushima Daiichi Nuclear Power Plant, but significant challenges still remain.
This report presents the current situation at the Fukushima Daiichi Nuclear Power Plant and the
responses by Japanese authorities and the international community since the accident. It will assist both
policymakers and the general public to understand the multi-dimensional issues stemming from theaccident. These include disaster recovery, compensation for damages, nuclear safety, nuclear regulation,
radiation protection, plant decommissioning, radioactive waste management, psycho-social issues in thecommunity and societal resilience.
Building on two previous reports released by the OECD Nuclear Energy Agency (NEA) in 2013 and 2016,
the report examines the plant’s future, that of the affected region and population, as well as outlining
areas for further improvement and how the international community can help.

Nuclear Energy Agency (NEA)
46, quai Alphonse Le Gallo
92100 Boulogne-Billancourt, France
Tel.: +33 (0)1 45 24 10 15
nea@oecd-nea.org www.oecd-nea.org

NEA No. 7558