Thermal conductivity of ceramics during irradiation

Thermal conductivity is one of the most important parameters for the design of fusion reactors using ceramic materials. Thermal diffusivity of ceramics decreases by phonon scattering and specific heat increases slightly as the temperature rises to 1300 K. The amount of point defects during neutron irradiation changes with the irradiation temperature. In this work, α -Al2O3, AlN, β -Si3N4 and β -SiC specimens were irradiated in the experimental fast reactor JOYO at 775, 835 and 1039 K to high neutron fluence. Thermal diffusivity was measured at elevated temperatures in vacuum via the laser flash method. Using an approximation function, the thermal diffusivity at the irradiation temperature was determined for each specimen, and the one during irradiation was estimated with additional assumptions. Thermal diffusivity of ceramics during irradiation was found to be almost temperature independent, and the thermal conductivity has a slight increase with temperature.