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Abstract. Low activated materials such as ferritic steel, vanadium alloy and SiC/SiC composite have to be developed for realization of a fusion demonstration reactor. Major issues concerning these low activated materials have been evaluation of neutron irradiation effects and feasibility as blanket materials. Since these are also in-vessel materials, issues of plasma material interactions have to be investigated. Ferritic steel, F82H, is well oxidized in the atmosphere. Thus, pre-baking is necessary before installation. The required baking temperature is higher than 900 K. Vanadium alloy, V-4Cr-4Ti, absorbs hydrogen well and hydrogen embrittlement takes place when the hydrogen concentration exceeds a critical level. In order to avoid hydrogen absorption, the formation of an oxide layer on the alloy was found to be very useful. In JFT-2M, the vanadium alloy was exposed to a deuterium discharge environment for 9 months. On the alloy surface, an oxide deposition layer with a thickness of 200 nm was formed. The deuterium concentration observed was very low, only 1.3 wppm. SiC/SiC composite may be employed as divertor plates in addition to its use as blanket material. Fuel hydrogen retention was very similar to that of graphite but the chemical erosion was negligibly small.
IAEA 2001
