Study on tritium accountancy in fusion DEMO plant at JAERI

Nishi, Masataka; Yamanishi, Toshihiko; Hayashi, Takumi; DEMO Plant Design Team

The fusion DEMO plant is under designing at JAERI as a fusion machine following ITER, and it is designed with long-term steady operation and tritium breeding blanket in which more tritium is produced than consumption. Therefore, proper tritium accountancy control concept should be discussed and developed for its safety and operation. From the viewpoint of regulation for the radioisotopes, at first, it will be suitable to divide facilities of the fusion DEMO plant into three accountancy control blocks, that is, (1) the contaminated waste management facility, (2) the long term tritium storage facility, and (3) the fuel processing plant. In each block, tritium amount of receipt and delivery should be carefully accounted. The fuel processing plant involves tritium production in the blanket, therefore proper accounting method for produced tritium should be established. Furthermore, dynamic accountancy is indispensable to the fuel processing plant to monitor tritium inventory distribution for safety and optimum system control in addition to the accountancy under regulation.