Plasma Material Interaction Study on Low Activation Materials Used for Balnket and First Wall in Fusion Reactor

T. Hino (Sp), Hokkaido University, Sapporo (JP) 
ssues of plasma material interactions for low activation materials such as ferritic steel, vanadium alloy and SiC/SiC composite have been investigated at Hokkaido University.
Ferritic steel, F82H, was irrdiated by 1.7 keV deuterium ions. The amount of retaied deuterium in F82H was observed to be lower than that in stainless steel, 316L SS. The physical sputtering yield of F82H was 0.04 atom per ion, comparable with that of 316L SS.
Vanadium alloy, V-4Cr-4Ti, was irradiated by deuterium ions. The deuterium concentration of vanadium alloy was lower than a critical concentration for hydrogen embrittlement, when the temperature was taken a balnket operation temperature, 900 K. The helium retention of vanadium alloy was also examined after the helium ion irradiation. The amount of retained helium was comparable with those of other plasma facing materials, graphite, SiC, B4C and W.
Helium gas permeability was measured for SiC/SiC composite. The SiC/SiC composite made by NITE process showed very low permeability, so that the blanket module may be produced using only SiC/SiC composite. However, a vacuum pumping for inside of blanket module is required to avoid the increase of helium concentration in a plasma. The change of permeability due to heat cycles was also measured. The temperature was increased up to 1300 K. A number of heat cycle was taken up to 120. The increase of permeability was avoided when the heating speed in the heat cycle was taken low.
The present results contribute to the design of first walls and blanket module in fusion demonstration reactor.

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