Current Nuclear Reactor Safety R and Ds and Trends in Japan

This paper provides a cursory look at the nuclear reactor safety regulation system and research programs in Japan relevant to nuclear reactor thermal hydraulics in general. After an introduction to Japanese nuclear power program, the nuclear regulation system is briefly described, and nuclear research infrastructure including research institutes and supporting organizations are outlined. In the matured stage of nuclear energy deployment in Japan, safety researches are focused onto those of ensuring the public safety, further improving and reinforcing the safety performances of the current and future nuclear installations, and enhancing nuclear safety regulatory activities. Among them, the prioritized nuclear safety research program is picked up and a brief look at several topics is made in connection more or less to thermal hydraulics. They include those of future risk-informed regulation, material degradation mechanisms principally concerning SCC and ageing management of nuclear power plants, severe accident issues, accident management, code development efforts in the areas of fuel behaviours, core thermal hydraulics, neutronics-thermal hydraulics coupling for high burn-up UO2 and MOX fuelled LWRs with corresponding experimentation, and a series of development programs of safety analysis methods for sodium cooled fast reactors of the next generation. (authors)