Safety assessment of nuclear power plant under volcanic phenomena part2-revision of JEAG4625 on the safety assessment of severe accident measures equipment and maintenance programme

Japan is one of the countries with abundant active volcanoes. In the field of Nuclear Energy, it is necessary to assess safety against volcanic hazards, and voluntary guidelines were published in JEAG4625 in 2009 to set up the requirements of site assessments and the basic designs of nuclear power plants (NPPs). Revised guidelines were published in 2014, which stated the need to examine volcanic phenomena and concrete countermeasures in the detailed designs of NPPs. A further revision included the requirement of the safety assessment of equipment used for measures in a severe accident. This paper focuses on the background and technical basis of the revision of the voluntary guidelines and shows the basic policy on the concept of defence in depth for protecting NPPs against volcanic phenomena and the requirements of equipment to perform measures in the case of a severe accident to prevent nuclear hazards due to volcanic phenomena and the maintenance programme after a volcanic eruption.