Degree of conservatism/margin of estimated tritium releases for HCCR-TBS

Korea has developed a Helium Cooled Ceramic Reflector (HCCR) TBM to be tested in the ITER. It consists of two major loops, which are HCS (Helium Cooling System) and TES (Tritium Extraction System) (figure 1). Tritium is one of the most highly permeable molecule on earth, therefore tritium permeation takes place from TES to HCS in the TBM. Permeated tritium migrates along the system pipes and tritium release in port cell and port interspace area is one of important safety issues for human access. Tritium is radioactive molecule which is 12.3 years of half-life. It is difficult to find good property reference for the HCCR TBS and other fusion application. This paper summarizes degree of conservatism/margin of estimated tritium releases for HCCR-TBS. Degree of conservatism/margin of estimated tritium releases for HCCR-TBS has been assessed with respect to possible items. TES and CPS performance increase methods give big impact on entire HCCR TBS design, therefore, it is just possible design option at this level of detail. In this regard, 20 ~ 2000 of conservatism/margin could be suggested in total. Tritium permeation issue in fusion industry is critical and has huge uncertainty to get realistic release rate. It is the fact that permeability is highly depended on operational temperature and surface condition. Practically it is expected that tritium amount in human access area for fusion reactor is negligible or manageable, however, dynamic and multi-dimensional tritium release analysis could be a solution for detail estimation.