Purity and radioactive decay behaviour of industrial 2D-reinforced SiCf/SiC composites

Ceramic matrix composites based on SiC with continuous fibres (SiCf/SiC) are considered promising structural materials for future fusion devices. It was still to clarify, whether impurities in industrial SiCf/SiC could jeopardise radiological advantages. Experimental impurity analyses revealed a two-dimensionally reinforced SiCf/SiC with the matrix produced by CVI as very pure. Chemo-spectrometric methods were combined with radioactivation methods (CPAA, NAA). A quantification of the main constituents Si, C and O was added. Calculations with the FISPACT-2.4 code and EAF-2 library identified elements detrimental for different low-activation criteria. For the neutron exposure, EEF reactor-study first wall and blanket conditions were simulated. The calculated SiCf/SiC included 48 trace elements. Even under conservative assumptions, all low-activation limits of European interest are fulfilled. Exclusively the hands-on recycling limit for the First Wall can intrinsically not be satisfied with SiC. The theoretical goal of a SiCf/SiC depleted of 28Si (isotopic tailoring) is critically discussed. ((orig.))