OVERVIEW

In fusion demonstration reactors, use of low activation materials has been required for a safety of fusion plant. Major concern on low activation materials has been on the material damage due to neutron irradiation so far. However, these materials are also used as plasma facing components and then the plasma surface interactions have to be investigated. In the present study, interactions of ferritic steel with plasma ions, fuel hydrogen absorption of vanadium alloy and helium gas permeation in SiC/SiC composite were investigated to clarify the suitability of the low activation materials.

The ferritic steel had ion sputtering yield similar to stainless steel, although in the surface the fuel hydrogen retention differed with that of the stainless steel. The vanadium alloy causes the hydrogen embrittlement due to a large hydrogen absorption. In order to reduce the hydrogen absorption speed, the use of titanium oxide coating was found to be very effective. The SiC/SiC composite is employed as blanket material, and then the concern is permeation of helium gas coolant. The SiC/SiC composite recently developed showed extremely low permeability. Then, this material can be used for the blanket without a metal...