Ceramics for fusion reactor applications

Ceramics are required in fusion reactors to serve as neutral beam injector insulators, dielectrics for RF heating systems, the toroidal current break, and magnet and direct converter insulators. Ceramics may also be needed for low-Z first wall structures, armor, limiters or divertor collectors. The characteristically severe operating conditions for these materials can result in significant degradation of bulk physical properties. Irradiation-induced changes in density, mechanical strength,, thermal and electrical conductivity, dielectric breakdown strength, loss tangent, and DC electrolytic behavior must especially be considered. This paper reviews radiation effects in a number of candidate ceramics, including Al2O3, MgAl2O4, Si3N4, MgO, sialon, and SiC, and discusses their potential for use in the above applications. Techniques are proposed for optimizing ceramic performance based on current understanding of radiation damage mechanisms, and areas are specified where further studies are critically needed. (author)