Fukushima Daiichi nuclear accident
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On 11 March 2011, Japan was struck by a massive earthquake of magnitude 9.0 on the Richter scale, which initiated a tsunami that inundated 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 and the entire facility was severely damaged. Post-accident analyses have verified that the radiation from the accident has not led to any direct impact on human health. However, the health and well-being of 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 operating reactors at the Fukushima Daiichi nuclear power plant quickly and effectively shut down as designed when the earthquake struck. 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) overheated and 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.

After nine months, the immediate risks posed by the damaged reactors were brought under control by achieving cold shutdown of the facility. In the years since, Japanese authorities have undertaken 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.

NEA's work

The Agency and its membership have been very active in understanding, assessing, and responding to the Fukushima Daiichi accident since it occurred in 2011. The NEA continues sharing and applying the many lessons learnt from this experience.

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 more tolerant 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 and Lessons Learnt, many such measures have been implemented.

To address near-term challenges in handling very low-level post-accident radioactive waste, the NEA 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 in decision making, have been a significant focus of NEA activities. The 2021 report Fukushima Daiichi Nuclear Power Plant Accident, Ten Years On: Progress, Lessons and Challenges details the range of such initiatives, as well as the activities of other international organisations.

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In 2019, the NEA Committee on Radiological Protection and Public Health's(CRPPH) Working Party on Nuclear Emergency Matters (WPNEM) created the Expert Group on Non‑radiological Public Health Aspects of Radiation Emergency Planning and Response (EGNR) to provide input to the WHO framework for mental health and psychosocial support in radiological and nuclear emergencies and to work on an operational extension of that document. The EGNR report will deliver guidance to decision makers in member countries while planning for, responding to, and recovering from nuclear or radiological emergencies by providing practical solutions, approaches and tools to integrate mental health and psychosocial support into protective action plans.