Nuclear plant severe accidents: challenges and prevention

A number of high-profile investigations on the cause of and the lessons learned from the Fukushima accident and the lessons learned were initiated after the accident. Implementations of the lessons learned have resulted in the new post-Fukushima safety requirements, for example, in Japan and the United States, and have also led to an update of the International Atomic Energy Agency safety standards to assure safety of the commercial light water reactors worldwide against severe accidents. Implementation of the new safety requirements to existing nuclear plants has been ongoing in Japan, while that of the US plants has been completed. This chapter focuses on (1) the updated understanding of the Fukushima accident, with additional insight from accident analyses that were not available at earlier years; (2) the lessons learned; (3) the development of new post-Fukushima safety regulations for coping with beyond-design-basis accidents; and (4) the implementations of the safety regulations in nuclear power plants in Japan and the United States.