Comparison of coolant conditions in the blanket for a water-cooled DEMO reactor SlimCS

Someya, Yoji; Tobita, Kenji; Uto, Hiroyasu; Takase, Haruhiko; Liu, C.; Asakura, Nobuyuki

Conceptual design of an alternative tritium-breeding blanket for SlimCS has been studied. The proposed blanket concept is that LiSiO pebbles or LiO pebbles for the tritium breeding and BeTi pebbles for the neutron multiplication are mixed and these pebbles are filled in the blanket. The coolant condition was selected to be sub-critical water, whose temperature difference between inlet and outlet were 290C and 360C, respectively, and pressure was 23 MPa. When LiO pebbles were mixed with BeTi pebbles, higher TBR was obtained, being greater than 1.05 for the blanket with the thickness of 0.48 m. However, the compatibility of the blanket structural material (F82H) with the sub-critical water is a concern. As the second step, therefore, we replaced the condition by the PWR water condition of 15.5 MPa and 290-330C to improve the compatibility with F82H. In addition, the PWR water has an advantage that matured technologies in nuclear power plants will be likely to reduce development risks in fusion plant engineering. Therefore, consideration of coolant plumbing was decreased from all length in blanket. On the other hand, use of the PWR water to the blanket requires a reduction of coolant plumbing length to meet the temperature range. The proposed blanket was assessed with an ANIHEAT code, and the two cases of coolant conditions were compared.