Silicon carbide and the new low activation requirements for a fusion reactor first wall

The radioactive behaviour of silicon carbide is compared to that of other structural materials proposed for fusion applications. This analysis takes into account short- and long-term issues like accident safety, maintenance and waste management. Low activation criteria based on the compliance with radioactivity limits are proposed. According to these criteria, steels can hardly be considered as possible low-activation materials. Even the elementally-tailored reduced activation steels can never fulfil completely all criteria. Vanadium alloys and SiC in the form of a new ceramic matrix/ceramic fibre composite ('SiC/SiC') must be regarded as the most promising low-activation materials, as far as radiological/activation behaviour is concerned. Some of the problems associated with the activation of vanadium alloys are examined. SiC/SiC turns out to be an ideal low-activation material as all criteria are fulfilled. Attention is given to the activation of SiC impurities. (orig.)