Fukushima Daiichi nuclear accident

On 11 March 2011, a massive earthquake of magnitude 9.0 on the Richter scale jolted the eastern coast of Japan. An hour after the earthquake, a 14-15 m tsunami, as estimated at the Fukushima Daiichi site, hit the Pacific coastline and led to a terrible loss of lives (approximately 19 000 people died or remain unaccounted for). It also led to loss of all onsite power sources resulting in serious accidents at the three operating Fukushima Daiichi units, which were classified by the Japanese authorities as level 7 on the International Nuclear and Radiological Event Scale (INES).

The accidents at Fukushima Daiichi Units 1, 2 and 3 were the result of the loss of offsite power caused by the earthquake, coupled with the loss of onsite power and the ultimate heat sink caused by the tsunami. Without a source of electrical power, the systems and components used to keep the fuel in the reactors cooled were not able to function. Although the operator attempted to implement alternative measures to cool the fuel, ultimately they were unsuccessful in preventing the fuel from overheating and melting. In addition, hydrogen generated during the accidents collected within the reactor buildings and caused explosions in the upper portions of the Unit 1, 3 and 4 reactor buildings, with significant damage to the top floors and exposure of the spent fuel pools to the environment.

In response to this accident, NEA member countries decided to alter the work priorities of the NEA standing technical committees in order to assess the accident and to identify safety lessons.

Work is being carried out on:

In addition, the NEA has devoted significant efforts to directly supporting the technical needs of the Japanese government, with this assistance primarily focusing on 1) the recovery of land and decontamination, 2) the development and implementation of national reviews and stress tests and 3) enhancements to the regulatory infrastructure.

Nuclear regulation

Actions taken by regulatory bodies and international organisations following the Fukushima Daiichi nuclear accident
A repository of information from 23 countries as well as 4 regional and 3 international organisations on national response activities, stress tests reports and complementary assessments and activities to the stress tests.

Report on the actions taken by the NEA member countries and standing technical committees in response to the Fukushima Daiichi NPP accident
The report entitled The Fukushima Daiichi Nuclear Power Plant Accident: OECD/NEA Nuclear Safety Response and Lessons Learnt was published in September 2013. It outlines international efforts to strengthen nuclear regulation, safety, research and radiological protection in the post-Fukushima context.

Precursor events
A review of previous operating events that have significant similarities to the Fukushima Daiichi NPP accident has been performed to address the following questions:

Some responses and operating experience lessons learnt from the accident at Fukushima Daiichi are provided in the report on Fukushima Daiichi NPP precursor events issued in January 2014.

Regulation of nuclear site selection
The "Supplementary Report on the Regulation of Site Selection and Preparation" was issued in July 2014. It addresses additional siting issues, such as assessing impacts of multi-unit sites, seismicity, security, specific design features of the NPP against the fixed site parameters and public consultation during siting. It also provides more details on regulatory approaches for new reactor siting including changes or enhancements as a result of the Fukushima Daiichi NPP accident.

Defence-in-depth (DiD) concept and implementation
A workshop on Challenges and Enhancements to DiD in Light of the Fukushima Daiichi NPP accident was held on 5 June 2013. Consequently, a Senior Task Group on Defence-in-depth had been set up, inter alia, to produce a booklet in the NEA regulatory guidance series – commonly known as Green Booklets – in order to assist member countries in re-considering and clarifying DiD and its implementation in light of the Fukushima Daiichi NPP accident.

Nuclear regulators effectiveness and safety culture
The green booklet describing The Characteristics of an Effective Nuclear Regulator in terms of roles and responsibilities, principles and attributes was published in July 2014. In the same vein, another green booklet is under preparation to cover the policy aspects of the higher level attributes and behaviours that create a safety culture of the regulatory body.

Accident management
A three-year mandate of the Task Group on Accident Management (TGAM) has been established to review accident management practices in light of the Fukushima Daiichi NPP accident. Its objectives include identifying measures that should be considered to enhance the regulations and regulatory guidance for operators’ accident management activities. In February 2014, the task group published a report on accident management insights after the accident at Fukushima Daiichi. It is built on the existing bases for capabilities to respond to design basis events and accidents at NPPs, and what additional measures should be considered as an accident progresses to the severe accident stage.

NEA met with Japanese officials to discuss nuclear safety regulatory organisations
An NEA team of international experts met in Tokyo on 17-18 January 2012 with members of the Japanese Advisory Committee for Prevention of Nuclear Accidents and the special Japanese Task Force for the Reform of Nuclear Safety Regulations and Organisations to foster increased understanding of various national regulatory organisations and approaches to regulatory oversight of nuclear power facilities.

The Fukushima Accident: Insights and Approaches
A meeting of nuclear regulatory authorities of the G8, NEA member countries and other associated countries (Brazil, Bulgaria, India, Romania, South Africa and Ukraine) was held on 8 June 2011 to discuss insights gained in relation to the accident and decide on appropriate follow-up actions at the international level.
Proceedings of the Forum on the Fukushima Accident: Insights and Approaches

New avenues for improving international nuclear safety
An International ministerial meeting co-organised by the French Presidency of the G8 and the NEA, with 37 countries in attendance was held on 7 June 2011.

Nuclear safety and research

New Expert Group on Accident Tolerant Fuels for LWRs
Following two workshops held in 2012 and 2013 at the NEA, an Expert Group on Accident Tolerant Fuels (EGATF) was established within the Nuclear Science Committee in June 2014. This expert group will define and carry out a programme of work to help advance the scientific knowledge needed to provide the technical underpinning for the development of advanced LWR fuels with enhanced accident tolerance compared to currently used zircaloy/UO2 fuel systems. In particular, the proposed group will foster information exchange on material properties and relevant phenomenological experiments, carry out state-of-the-art reviews, organise benchmark studies and foster international collaborations regarding the development of core materials and designs which provide an improved tolerance to accidents.

NEA / Japanese nuclear safety authority meeting on national safety reviews / stress tests
NEA experts met in Tokyo with the Japanese Nuclear and Industrial Safety Agency (NISA) and the Japan Nuclear Energy Safety Organisation (JNES) on 16-18 November 2011 to foster a better understanding by NISA and JNES of other NEA member countries' post-Fukushima national safety reviews/stress tests, international guidance and review methodologies.

Fukushima safety research activities

Eight priority safety research activities were identified to address issues arising from the accident at Fukushima Daiichi:

Joint nuclear safety research projects

For more than 30 years, the NEA has provided a platform for interested countries to co-operate on a cost-sharing basis and pursue research on particular areas that would be difficult to deliver on a national basis.  Following the Fukushima Daiichi NPP accident, an NEA review of the joint research projects was carried out in 2012 known as Main Benefits from 30 Years of Joint Projects in Nuclear Safety (ISBN 978-92-64-99171-2), where a number of projects were identified that were already examining safety aspects of the accident.

Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station (BSAF)
A joint project was initiated in 2012 called, Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station (BSAF). Eight member countries (Japan, France, Germany, Korea, Russia, Spain, Switzerland and the USA) are conducting a modelling study of the first six days of the accident. The first phase of the project is nearing completion, and discussions are underway for a second phase to begin in 2015.

Three specific Fukushima-initiated projects

Following the accident and this report, the NEA safety committees initiated three new joint projects based on existing research facilities to address safety issues related to the accident. These were HYMERES, PKL-3 and ATLAS.

Further information on these and other joint projects can be found under NEA joint projects.

Crisis communication

NEA Working Group on Public Communication of Nuclear Regulatory Organisations (WGPC)
The WGPC addressed the international dimension of the communicative responses to crises by assessing the experience of nuclear regulatory organisations (NROs) of NEA member countries and their stakeholders. Within this framework, a crisis communication workshop was held in Madrid on May 2012 and the report, Crisis Communication of Nuclear Regulatory Organisations: Towards global thinking, was issued in June 2013. In order to constantly improve communication, NROs invited external stakeholders to public communication workshops. The International Workshop with Stakeholders was held in April 2014. The next ones are scheduled for 2015 and 2016 in North America and Asia, respectively.

Radiological protection

International meetings on remediation and restoration of environments
The NEA co-organised two days of international meetings on The Experience and Technology of Russia, Ukraine and Other CIS Countries on Remediation and Restoration of Environments on 3-4 February 2012. The meetings provided opportunities for experts from zones most affected by the Chernobyl accident to share best practices in managing contaminated land.

Decontamination and recovery

International Symposium on Decontamination held in Fukushima, Japan
The Government of Japan, in co-operation with the International Atomic Energy Agency (IAEA), the OECD Nuclear Energy Agency (NEA), the Japan Atomic Energy Agency (JAEA) and the Japan Nuclear Energy Safety Organisation (JNES), held an International Symposium on Decontamination – Towards the Recovery of the Environment, in Fukushima, Japan on 16 October 2011.

Nuclear liability and compensation

Japan's Compensation System for Nuclear Damage As Related to the TEPCO Fukushima Daiichi Nuclear Accident
The NEA has prepared this publication in co-operation with the government of Japan to share Japan's recent experience in implementing its nuclear liability and compensation regime. The material presented in the publication should provide valuable insights for those wishing to better understand the regime applied to compensate the victims of the accident and for those working on potential improvements in national regimes and the international framework for third party nuclear liability.

Further information

OECD Nuclear Energy Agency (NEA) follow-up to the TEPCO Fukushima Daiichi nuclear accident
Extracts from NEA News
The NEA has undertaken a number of activities following the March 2011 accident at the Fukushima Daiichi nuclear power plant in Japan. This brochure contains three extracts from NEA News published in the months following the accident: Fukushima (what happened, consequence, follow-up), published June 2011; Fukushima: liability and compensation, published December 2011; and The NEA integrated response to the Fukushima Daiichi nuclear accident, published June 2012. Together these extracts help the reader to better understand the causes, consequences and importance of the NEA's response to the Fukushima Daiichi accident (2012).


Last reviewed: 15 September 2014