Welcome to the OECD/NEA press kit on Fukushima. Here you will find information on the Fukushima Daiichi nuclear power plant accident of 11 March 2011 and its implications for nuclear safety and radiological protection. There are also easy reference FAQs on the accident, and links to further online resources and documents.
The Fukushima Daiichi nuclear accident of 11 March 2011 resulted from the massive Tohoku earthquake (magnitude 9.0 on the Richter scale, one of the largest ever recorded in Japan) and the ensuing tsunami that hit the country’s Pacific coastline. The earthquake’s epicentre was situated 150 km north-east of the two Fukushima nuclear power plants (Daiichi and Daini) operated by the Tokyo Electric Power Company (TEPCO). The Onagawa nuclear power plant (operated by the Tohoku Electric Power Company) was the closest to the epicentre, at approximately 80 km. In total, 11 operating reactors affected by the earthquake shut down immediately.
Of the six reactor units at the Fukushima Daiichi site, three were operating at the time: units 1, 2 and 3. These units did shut down safely following the earthquake, but the earthquake caused the electric grid to collapse and offsite power supplies were lost. The onsite emergency diesel generators (EDGs) started and provided electrical power to emergency systems that began operating almost immediately after the earthquake (for more detailed information on the boiling water reactors (BWRs) used at Fukushima Daiichi, see BWR Design Basics).
However, about one hour after the earthquake, a tsunami estimated at 14-15 m struck the site. The height of the tsunami was approximately ten metres higher than estimated in the plant’s design. This caused wide-scale flooding of the site and the subsequent failure of all EDGs (with the exception of one air-cooled EDG at unit 6) as well as the pumps that provided cooling water from the "ultimate heat sink”. This is a term used for a complex cooling system used by nuclear power plants such as a river or sea, in this case the Pacific Ocean.
Had the initiating events at Fukushima Daiichi stopped with just the earthquake, the extent of the accident would have been significantly less. This was demonstrated by the significantly lower level of releases of radioactive material and subsequently reduced impact to the public and environment from the nearby Fukushima Daini nuclear power plant. At Fukushima Daini, one source of offsite electrical power remained available to provide power to the critical equipment needed to shut down and to cool the reactors.
With the loss of onsite and offsite electrical power at Fukushima Daiichi, all the safety systems that started after the earthquake and relied on electrical power to meet their function to protect and cool the fuel in the reactor cores at units 1, 2 and 3 failed. The systems that did not rely on electrical power were available for a short time following the accident. However, they also eventually failed. At that stage, both power supplies and access to the ultimate heat sink for cooling had been lost. When cooling of the reactor cores at units 1, 2 and 3 was lost, significant damage to the nuclear fuel occurred. Core melting was predicted to have begun at unit 1 several hours after the tsunami, at unit 3 on 13 March and at unit 2 on 14 March. For a day-by-day account of events, see the NEA Fukushima Daiichi accident timeline.
In addition to this reactor core damage, 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. This meant that the spent fuel pools in these buildings were exposed to the environment and radioactive materials were released. In total, radioactive material was released from four reactor buildings. The ability to add water to the spent fuel pools was also lost and resulted in reduced cooling capacity of the spent fuel pools without, however, damage to the fuel itself.
The accident was rated 7 on the International Nuclear Events Scale (INES) due to the major release of radioactive material and widespread environmental effects. However, the Fukushima accident differs from the only other nuclear event rated at level 7, the Chernobyl accident, because no widespread health effects were caused. For this reason, a revision of the INES scale may be performed to incorporate the lessons learnt from the application of the INES criteria to the Fukushima Daiichi accident.
Following the accident, every country with operating nuclear power plants conducted initial assessments of the continued safe operation of its plants. More thorough evaluations of the accident and its impact on safety were also undertaken. These have been called safety assessments or "stress tests”.
The stress tests evaluate the responses of a nuclear power plant to severe external events (single and multiple). They consider the initiating events, the consequential loss of safety functions and the management of a severe accident. Both the NEA and the IAEA have played a significant role in the exchange of related information among countries.
Stress tests in the European Union (EU) began on 1 June 2011, and were performed according to the specifications adopted by the European Nuclear Safety Regulators’ Group (ENSREG). The results are online. In addition to EU members, a number of non-EU countries (Armenia, Belarus, Croatia, Russia, Switzerland, Turkey and Ukraine) agreed to carry out stress tests using the EU methodology. National safety assessments have also been or are being carried out in Canada, Japan, Mexico, the Republic of Korea and the United States. The results are online.
The Fukushima Daiichi nuclear accident has demonstrated a need for nuclear regulators to improve power plant designs to prevent an accident, but also to mitigate an accident if it occurs. The potential safety improvements identified have therefore been technical in nature, but also organisational.
The NEA Committee on Nuclear Regulatory Activities (CNRA) has established the Senior-level Task Group on Impacts of the Fukushima Accident. Specific questions raised by the accident include the following:
The accident at Fukushima Daiichi also raised the significant technical challenge of dealing with prolonged loss of electrical power, or station blackout. The NEA is working towards improved predictive data and modelling to form a better understanding of how plants would respond if the power supply is cut for long periods.
In view of the hydrogen explosions which severely impacted units 1-4 at Fukushima Daiichi, the generation and transport of hydrogen following core damage is also being examined. Lessons can also be learnt on the impact of nuclear accidents on the ability to protect fuel stored in spent fuel pools. At Fukushima Daiichi, spent fuel pools were exposed to the environment. Their protection is therefore an important issue.
Work is currently being undertaken by the Multinational Design Evaluation Programme (MDEP), an independent group of regulatory authorities, to review the impact of the Fukushima Daiichi accident on two specific reactor designs: the Areva EPR and the Westinghouse AP1000.
The design implications from the Fukushima accident are also being factored into the designs of the next generation of nuclear reactors through the work of the Generation IV International Forum (GIF).
Currently nuclear regulators and industry use two basic analytical approaches for evaluating nuclear safety. The probabilistic approach is based on the likelihood of something occurring. With a deterministic approach, there exists the assumption that there will be a failure of some kind. Following the Fukushima Daiichi accident, these concepts will be better balanced for evaluating nuclear safety in both technical and organisational areas to ensure that nuclear power is made even safer.
Immediately after the Fukushima Daiichi accident and the start of the release of radioactive substances from the power plant, the Japanese government recommended the evacuation of the 78 000 people living within 20 km of the plant. It also recommended the sheltering of approximately 62 000 people living between 20 and 30 km from the plant, and the evacuation of a further 10 000 people living further to the north-east of the plant which was determined to be the most contaminated area. Because of these rapid government measures, health-significant exposure to radiation was avoided (see Fukushima FAQs for more information).
Currently evacuation zones are defined on the basis of the expected exposure of the public to radiation (in millisieverts, mSv). In Japan, the reference level is 20 mSv per year. This means that if members of the public are expected to receive more than a 20 mSv dose in a year they must be evacuated. Following the accident, the Japanese government chose these criteria based on the latest recommendations of the International Commission on Radiological Protection (ICRP).
In the event of an accident, for most nuclear power plants around the world, it is expected that people located within a 5 km radius will be evacuated. At Fukushima Daiichi, the evacuation zone was 20 km and in some circumstances out to 30 km.
The workers on site at Fukushima Daiichi are the population most highly at risk from radiation effects, due to both immediate effects from extremely high exposures, and longer-term effects from smaller doses. Under normal working conditions, any worker who is exposed to radiation as part of his or her job is allowed no more than 100 mSv of exposure over a five-year period, with exposure in no single year to exceed 50 mSv. Under extreme and emergency situations, international recommendations allow emergency workers to receive up to 500 mSv.
As of 15 June 2011, approximately 2 400 workers had been exposed as a result of recovery work at the Fukushima plant. Of these workers, 8 had received exposures over 250 mSv. This was the limit for emergency workers set by the Japanese Ministry of Economy, Trade and Industry (METI) and the Ministry of Health, Labour and Welfare on 15 March 2011. All worker exposures continue to be monitored, and those exceeding the emergency criteria will most likely be followed medically, although radiation effects such as cancer and leukaemia remain unlikely even in these workers.
Until local residents around Fukushima return home, it is the national government that will continue to take decontamination initiatives. The basic policy in areas of high contamination is to rapidly reduce radiological exposure through extensive decontamination work. This applies in areas where radiological exposures of 20 mSv per year or more are estimated. However, the Japanese government has also set a longer-term objective of reducing the additional annual dose received by the public to 1 mSv per year.
The Japanese authorities have specified by how much they intend to decontaminate affected areas where people live. For the general public, there is a provisional objective of reducing annual radiological exposure by 50% in two years. Decontamination efforts will account for 10% and natural radioactive decay will account for 40% of this reduction. For children, the authorities have specifically targeted a 60% reduction in annual exposure over the next two years. This is to be achieved by targeted decontamination of the areas in which they live and play, such as schools or parks. Decontamination efforts will account for 20% and natural radioactive decay for 40% of this reduction.
For further information on decontamination, refer to the Fukushima FAQs.
The accident at Fukushima Daiichi nuclear power plant has raised the question of liability for the accident and the compensation of those affected. Although there have been no casualties due to radioactivity, the accident has nonetheless been responsible for the evacuation of thousands of people and for the loss of livelihoods, goods and property.
As the operator of the Fukushima Daiichi nuclear power plant, the Tokyo Electric Power Company (TEPCO) is exclusively liable for all the consequences of the accident including the indemnification of victims. In addition, the victims of the accident do not need to prove fault or negligence on the operator’s part to be compensated, because TEPCO is strictly liable for the accident. TEPCO also faces unlimited liability, which means compensation will not be fixed to a limited amount. This liability is, however, limited in time to 20 years from the date when the damage occurred. Victims must address claims within 10 years from the date that the person suffering damage has knowledge of both the damage and the operator liable, which in this case isTEPCO.
Under a nuclear liability regime, the operator of a nuclear power plant must have financial security (usually insurance), which in the case of TEPCO stands at Japanese yen (JPY) 120 billion. However, a Governmental Indemnity Agreement between TEPCO and the Japanese government was reached for this amount, to cover non-insurable risks, such as earthquakes and tsunamis.
As of 13 November 2015, JPY 5.6891 trillion (EUR 43 billion) had been paid in compensation for damages attributable to the accident. These figures may be subject to change as time progresses. (For updates, check the "Status of Indemnification payouts" on TEPCO's website)
The Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF) was established in September 2011 by the Japanese government and 11 national nuclear operators, to manage a fund which receives contributions from the nuclear operators which are shareholders of NDF in order to support these operators in providing compensation to victims of nuclear accidents. In case such contributions are insufficient, NDF may also receive funds from the Japanese government, through government bonds which amount will have to be reimbursed. Although established following the Fukushima Daiichi accident, NDF will continue to be maintained in the future as part of the Japanese nuclear liability regime. As of October 2015, TEPCO had received approximately JPY 5.6059 trillion (EUR 42 billion) from NDF. (See TEPCO's 22 October 2015 press release)
At the time of the accident, Japan was not a party to an international nuclear liability convention (since then, it joined the Convention on Supplementary Compensation for Nuclear Damage in April 2015), but its nuclear liability regime made similar provisions. Thus far, there has been no transboundary damage following the accident, and so liability and compensation issues fall under Japanese legislation.
Three main laws are applicable following the accident: the Civil Code, the Act on Compensation for Nuclear Damage (Compensation Agreement) and the Act on Indemnity Agreements for Compensation of Nuclear Damage (Indemnity Agreement).
For more information on nuclear liability and compensation in the case of the Fukushima Daiichi nuclear accident, see the NEA Publication "Japan's Compensation System for Nuclear Damage as Related to the TEPCO Fukushima Daiichi Nuclear Accident" (2012) and the December 2011 and 2014 issues of NEA News. For further information about nuclear liability regimes, see "Progress towards a global nuclear liability regime" (Nuclear Law Bulletin, No 93), as well as the International nuclear third party liability press kit.
The Fukushima Daiichi accident has drawn attention to the implications of the accident on the future cost of nuclear energy. It will take some time before the full impact is known, and it is still early to give a global indication of how the accident has affected costs. However, in general terms costs for nuclear energy could rise as new requirements following Fukushima become mandatory.
For further information on the economics of nuclear energy, see the Economics of nuclear power press kit.
The NEA is uniquely positioned to support Japan and the international community in moving forward to identify and to apply lessons learnt from the accident. With member countries and partners in Europe, North America and Asia, the NEA can bring together top technical and regulatory experts from mature nuclear industry and regulatory organisations.
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 allow the reader to understand better the causes, consequences and importance of the NEA's response to the Fukushima Daiichi accident.
In follow-up to the Fukushima Daiichi nuclear accident, the NEA is implementing the INFASE programme, or Integrated NEA Fukushima Actions for Safety Enhancements. The programme is headed by the Senior-level Task Group on the Impacts of the Fukushima Accident (STG-FUKU), which was set up by the NEA Committee on Nuclear Regulatory Activities on 23 March 2011.
Three NEA standing technical committees are principally involved in this Fukushima follow-up work: the Committee on Nuclear Regulatory Activities (CNRA), the Committee on Radiation Protection and Public Health (CRPPH) and the Committee on the Safety of Nuclear Installations (CSNI). Further information on the NEA committee structure can be found here.
The objective of the INFASE programme, through research, analysis and the sharing of experience, is to bring about improvements across a range of areas which will enhance nuclear safety and aid the recovery of those affected by the accident.
The NEA is addressing, in particular:
A summary report of key NEA actions and member country responses is currently being prepared and is expected to be published in 2013.
Improving the current knowledge base regarding the status of the reactor cores in units 1 to 3 of the Fukushima Daiichi nuclear power plant is a vital step in preparing for fuel debris removal and the dismantling and decommissioning of the power plant.
In November 2012, the NEA launched a benchmark study to improve severe accident codes and models and to further the understanding of severe accident progression. Eight countries comprising France, Germany, Japan, Korea, Russia, Spain, Switzerland and the United States are participating in the Benchmark Study of the Accident at the Fukushima Daiichi Nuclear Power Station (BSAF). Further information on the BSAF benchmark is available here.
The issue of hydrogen release into a nuclear power plant containment has been the subject of much focus since the accident at Fukushima Daiichi, where 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.
In this respect, the NEA launched the Hydrogen Mitigation Experiments for Reactor Safety (HYMERES) Project. This is a four-year research programme (2013-2016) using Switzerland's PANDA facility and France's MISTRA facility to provide data for resolving complex, safety-relevant issues for the analysis and mitigation of a severe accident caused by hydrogen release into a nuclear power plant containment. The project will involve Canada, the Czech Republic, China, Finland, France, Germany, India, Italy, Korea, Russia, Spain, Sweden and Switzerland.
On 9-10 May 2012, the NEA hosted the International Workshop on Crisis Communication in Madrid, Spain, in collaboration with Spanish regulatory authority the Consejo de Seguridad Nuclear. The workshop brought together senior-level regulators and communicators from nuclear regulatory organisations (NROs), along with other communication stakeholders from civil society, in order to share best practices and to improve NRO crisis communications based on lessons learnt after the Fukushima Daiichi nuclear accident.
A basic design philosophy of nuclear facilities is defence-in-depth, which provides multiple, independent levels of protection against the release of radioactive substances.
While the concept of defence-in-depth has been found to be valid, its implementation has raised challenges and needs to be further reviewed and improved, especially in light of events at the Fukushima Daiichi nuclear power plant.
The issue of defence-in-depth is addressed in NEA Director-General Luis E. Echávarri's speech "Forging a New Nuclear Safety Construct", delivered at the American Society of Mechanical Engineers (ASME) workshop on 3-5 December 2012 in Washington DC, United States. Extracts from Mr Echávarri's speech are available here.
The NEA is working to evaluate the methodologies for defining and assessing initiating internal and external events, including coupled events, as well as methodologies defining design-basis criteria. In this area, two NEA working groups are active: the Working Group on Risk Assessment (WGRISK) and the Working Group on Integrity of Components and Structures (WGIAGE).
Given the insights gained from the Fukushima Daiichi accident, it is important to evaluate operating experience for events that may be precursors to future events that could challenge the safety of nuclear power plants. In this area, through the Working Group on Operating Experience (WGOE) and the Working Group on Risk Assessment (WGRISK), the NEA is focusing on precursor events and probabilistic safety assessment (PSA) studies. The NEA is also conducting a review and analysis of previous NEA joint international research projects relevant to the analysis of the accident at Fukushima Daiichi.
Currently nuclear regulators and industry use two basic analytical approaches for evaluating nuclear safety. The probabilistic approach is based on the likelihood of something occurring. With a deterministic approach, it is assumed that there will be a failure of some kind. Following the Fukushima Daiichi accident, efforts are being undertaken to better balance these two concepts for evaluating nuclear safety in both technical and organisational areas to ensure that nuclear power is made even safer.
On 17-18 January 2012, an NEA team of international experts met in Tokyo 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. Participants discussed different approaches to reforming areas recommended by the Advisory Committee, such as those concerning independence, regulatory oversight, crisis management, human resources and development, new safety regulations, transparency and international aspects for regulatory organisations. Presentations are available on the NEA Fukushima information exchange page.
On 16-18 November 2011, an NEA team of international experts met in Tokyo with the Japanese Nuclear and Industrial Safety Agency (NISA) and the Japan Nuclear Energy Safety Organisation (JNES) to foster a better understanding by NISA and JNES of other NEA member countries' post-Fukushima national safety reviews (or "stress tests"). Experts from Japan, France, Finland, Korea, the United Kingdom, the United States and the International Atomic Energy Agency (IAEA) participated in these meetings. Presentations are available on the NEA Fukushima information exchange page.
Over 120 nuclear regulatory and industry experts met in Paris on 15-16 September 2011 to discuss the accomplishments of the Multinational Design Evaluation Programme (MDEP) and the future of global nuclear safety.
On 7 June 2011 in Paris, France, representatives of the G8 and NEA member and associated countries participated in the International Ministerial Seminar on Nuclear Safety following the Fukushima accident, which enabled important discussions on how to reinforce international co-operation and international legal frameworks on nuclear safety.
On 8 June 2011, the Forum on the Fukushima Accident: Insights and Approaches brought together the nuclear regulatory authorities of the G8, NEA member countries and associated countries including Brazil, India, Romania, South Africa and Ukraine. Participants discussed insights gained in relation to the Fukushima Daiichi accident and decided on appropriate follow-up actions at the international level. The conclusions of the ministerial seminar and the regulators forum were also communicated to the IAEA as part of the preparations for the IAEA Ministerial Conference on Nuclear Safety of 20-24 June 2011. Following that conference, the IAEA produced an Action Plan comprising 12 actions to strengthen the global nuclear safety framework following the Fukushima Daiichi accident.
In the area of radiological protection and public health, the NEA has, in collaboration with the International Commission on Radiological Protection, co-sponsored a series of public dialogues in Fukushima Prefecture on the rehabilitation of living conditions following the Fukushima Daiichi accident. This Fukushima Dialogue Initiative has focused on community and stakeholder co-operation, contaminated foodstuffs and the education of children and youth.
Date: 26-27 November 2011
Place: City of Fukushima, Japan
Details: The objective of the first meeting was to foster dialogue between local actors involved in the rehabilitation of living conditions in Fukushima Prefecture. Participants heard presentations on the situation in Fukushima, and on the lessons learnt from the Chernobyl nuclear accident. Two aspects of particular importance were raised: re-establishing the affected communities with safe living conditions and quality food products, and solidarity with other communities.
Date: 25-26 February 2012
Place: Date City, Fukushima Prefecture, Japan
Details: The second dialogue meeting focused on past accomplishments, current challenges and future initiatives to improve the radiological situation and living conditions for local inhabitants. The participants emphasised the human dimension of the situation, the particular importance of preserving the dignity of the population and of reinforcing local, national and international solidarity. Meeting participants recognised the need for a more detailed characterisation of the radiological situation to allow people to know where, when and how they are exposed.
Date: 7-8 July 2012
Place: Date City, Fukushima Prefecture, Japan
Details: The third dialogue meeting focused primarily on experiences related to contaminated foodstuff following the Fukushima Daiichi nuclear accident, addressing the concerns of local inhabitants and stakeholders. The discussions on food management involved a wide range of stakeholders including farmers, retailers, consumer organisations, teachers, parent-teacher associations, journalists, medical doctors and city/village officials. Participants came from the Fukushima prefecture as well as from Tokyo. Among the conclusions reached at the meeting was the decision to create a forum for a permanent dialogue among all parties concerned (producers, distributors and consumers) on the issue of foodstuff.
Date: 10-11 November 2012
Place: Date City, Fukushima Prefecture, Japan
Details: The fourth dialogue focused on the education of children, using the knowledge of the radiological situation in Fukushima Prefecture gained from the first three dialogues. Teachers from schools in Fukushima shared their experiences, and participants heard the lessons learnt in the areas in Norway and Belarus affected by the Chernobyl nuclear accident.
Date: February 2013 (tentative)
Place: Date City, Fukushima Prefecture, Japan
On 12-14 March 2012, the Japanese government and the Tokyo Electric Power Company (TEPCO) held an International Experts' Workshop and International Symposium on the Decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Plant Units 1-4 in Tokyo, Japan. This event was co-organised with the OECD Nuclear Energy Agency (OECD/NEA) and the International Atomic Energy Agency (IAEA). The event provided a forum for discussion and exchange of information among technical experts from Japanese utilities, research and design organisations, regulatory bodies, manufacturing and service companies, as well as other international experts on decommissioning, radioactive waste management and robotics. Attendees visited the Fukushima Daiichi nuclear power plant following the symposium.
On 3-4 February 2012, the NEA co-organised two days of international meetings in Tokyo, Japan, on The Experience and Technology of Russia, Ukraine and Other CIS Countries on Remediation and Restoration of Environments. The meetings provided opportunities for experts from zones most affected by the Chernobyl accident to share best practices in managing contaminated land.
On 16 October 2011, 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. Read more Watch video footage of the symposium
Last updated: 21 December 2015