Comparative radiological assessment of SiC/SiC composites as structural materials in nuclear fusion technology

The fusion technological consequences of the radioactive decay behaviour of SiC-based structural material were analysed based on a complete chemical analysis of an industrial SiCf/SiC composite. Radioactivation simulation was performed with the FISPACT-2 code and EAF-2 cross-section library, taking n-spectra from the SEAFP reactor study for first wall and blanket. The decay of radioactivity in SiCf/SiC after shut down and derived radiological quantities are presented and compared with those of SEAFP structural materials. The effective dose equivalent (EDE) to the population from accidental release of activated material was computed with the GENII code. SiCf/SiC performs favourably. Contact dose rates and γ-dose rates inside the plasma chamber are given. Assuming an upper limit of 104 Gy h−1 for robotized maintenance, SiCf/SiC renders the first wall a zone where immediate repair would be possible. For this short-term activation limit, an elemental “critical list” is presented. Long-term decay heat generation and contact dose rates show which material fulfils waste limits. Although Al-26 is generated in the first wall, SiCfSiC is a safely disposable material, owing to other characteristics such as inertness against corrosion.