Neutronic aspects of the safety and environmental performance of silicon carbide as blanket structural material

Safety and environmental assessments have been made of conceptual fusion po wer plant designs employing silicon carbide composites (SiC/SiC) as the fir st wall and blanket structure material. These have used similar analysis me thods to earlier studies of designs based on vanadium alloy or low-activati on martensitic steel, allowing direct comparisons. The very low short-term activation of silicon carbide results in an almost insignificant level of d ecay heat in postulated loss of coolant accidents, and a lower gamma -dose rate on the timescale of relevance to handling for maintenance operations. However on the longer time-scale, of interest in possible recycling operati ons, decommissioning and waste management, SiC/SiC appears to perform no be tter than vanadium alloy or low-activation martensitic steel, due in part t o the activation of impurities in a realistic composition. Furthermore, its increased neutron transparency may result in higher activation in the vacu um vessel and ex-vessel components, unless costly additional shielding is i ntroduced. (C) 2001 UKAEA Fusion. Published by Elsevier Science B.V. AU rig hts reserved.