Nuclear Applications for Ultra-High Temperature Ceramics and MAX Phases

Future nuclear reactor systems and the severe conditions under which they will operate are reviewed. Current nuclear applications of ceramics are predominantly as oxide fuels as well as ceramic/glassy waste forms, although non-oxides do find niche uses such as graphite moderators and B4C control rods. UHTCs properties of interest to the nuclear industry include that they may be fissile, and that they have high thermal conductivity, refractoriness, and phase stability. Using such properties, future nuclear ceramics will potentially include UHTCs, for example, as non-oxide fuels (U/Pu carbides and nitrides) and fuel cladding (TaC, ZrC, HfC). MAX phases may also find application as fuel cladding. Oxide and non-oxide composite (e.g., SiC/SiC) and inert matrix fuel systems are under development for future fission reactors while uses of ceramics in fusion reactor systems will be both functional (such as the ceramic superconductors in the magnet systems for controlling the plasma) and structural in various locations outside of the first wall in magnetic confinement fusion. Finally, the importance of thermodynamics in severe conditions and the need for accurate thermodynamics databases are highlighted.