PERIODICAL SAFETY REVIEW AND PROBABILISTIC SAFETY ASSESSMENT IN JAPAN

摘要

Currently 49 commercial nuclear reactors, representing some 40 GW, are in operation in Japan, and they have shown excellent stable performance in recent years. It is particularly important to implement comprehensive preventive maintenance actions in addition to strictly enforcing normal safety regulations, including those measures which are not legally mandatory, such as countermeasures after a severe accident, and the periodical safety review. The paper introduces the commitments to these preventive actions in Japan. In June 1992, the Ministry of International Trade and Industry (MITI) notified every electric power company that they would be required to implement periodical safety reviews (PSRs). The PSR is designed to incorporate the latest advances in technical knowledge and to reflect lessons learned from incidents and failures in Japanese and overseas nuclear power plants. The first series of PSRs have been applied to the three oldest nuclear power reactors, Tsuruga Unit 1, Fukushima Daiichi Unit 1 and Mihama Unit 1 since October 1992. These reviews were conducted with regard to the opinions of experts, and the results were published in August 1994. The second series of PSRs are currently being conducted on four older power reactors, Fukushima Daiichi Unit 2, Shimane Unit 1, Mihama Unit 2 and Genkai Unit 1. In July 1992, MITI requested every electric power company to perform studies on severe accident management measures for their nuclear power plants. At the same time, MITI established the Severe Accident Countermeasure Study Group under the Nuclear Power Generation Technical Advisory Committee, and started studies on severe accident issues by experts in this field. In March 1994, the electric power companies submitted accident management study reports for 51 plants in operation or under construction, and MITI studied the technical appropriateness of these reports while referring to the opinions of the Severe Accident Countermeasures Study Group. MITI announced in October 1994 that these study results were satisfactory, and reported to the Nuclear Safety Commission accordingly. The MITI report is currently being studied by the Deliberation Committee on Comprehensive Safety of Reactors of the Nuclear Safety Commission.