Design substantiation of ceramic materials on fusion reactor confinement boundaries

Ceramic components will be used for electrical insulation and optical transparency on the heating and diagnostic systems of fusion reactors. As these form the boundary for the radioactive confinement, a defined procedure is required to demonstrate structural integrity. The established design codes are incompatible with ceramic materials for various reasons, predominantly the brittle nature of ceramics. CCFE and others have started to develop an in-house design code for the use of brittle materials in pressure vessels, this paper discusses the rationale behind the rules. The difficulty of reconciling the statistical nature of failure in ceramics with the deterministic nature in codes is addressed and it is suggested that the only way to achieve this is by a proof testing approach. The inherent weakness of the proof testing methodology, quantifying the strength loss during the qualification test is discussed. Further work is required to determine the validity of the rules experimentally.