Evaluation of tritium permeation in solid breeder blanket cooled by supercritical water

Kosaku, Yasuo; Yanagi, Yoshihiko*; Enoeda, Mikio; Akiba, Masato

As a candidate DEMO blanket, the design of solid breeder blanket cooled by supercritical water has been performed. The candidate structural material is F82H. The coolant is supercritical water (pressure; 25 MPa, temperature; 550-780K) to achieve high generation efficiency. The temperature of cooling tubes in tritium breeder zone has been evaluated at 650-800K. In this temperature range, tritium permeation must be investigated from the view point of safety management, because high temperature coolant is directly supplied to the power generation system. In the present work, the tritium permeation into the first wall cooling water by the implantation and that through cooling tubes in tritium breeder zone have been evaluated. Assuming tritium injection energy and flux are same as SSTR, the calculated value of the tritium permeation rate into the first wall cooling water is 68.3 g/day. On the other hand, that of the permeation rate through cooling tubes is 75.3 g/day (20% of generated tritium) when helium gas flows so that tritium partial pressure becomes 1 Pa at the outlet.