Overview of tritium safety studies in Japan

Tritium safety is one of the most important R&D subjects for developing International Thermonuclear Experimental Reactor (ITER) and fusion reactor. In Japan, tritium safety studies are being conducted in JAERI (Japan Atomic Energy Research Institute), NIRS (National Institute of Radiological Sciences), and universities. In JAERI, experiments and experiences in Tritium Process Laboratory (TPL) are most important. Here, a few kilograms of tritium have been safely used from its start of operation in 1988. Recent important research subject is elucidation of tritium behavior in the tritium confinement system using a caisson (12 m5) combined with tritium removal system. JAREI is also conducting safety related studies such as, tritium confinement, tritium decontamination, tritium permeation, off-normal events, and tritium accountancy. In universities, various fundamental researches have been conducted, including tritium permeation, simulation of tritium behavior in the fusion reactor system, tritium contamination and decontamination, tritium measurement, tritium interaction with materials, and tritium trapping on the surface of various fusion reactor components. Tritium environmental behavior and biological effect are important subjects to evaluate the consequences of released tritium and to provide an appropriate information to receive good public acceptance for fusion reactor. Fundamental and code development studies related to them are being conducted in universities, JAERI, and NIRS. Licensing preparation for ITER is being conducted at the Government in the collaboration with JAERI. This includes safety features, fundamental approach for safety design, assessment of safety design features, and evaluation of the consequences of off-normal events.