High temperature thermal physical performance of SiC/UO2 composites up to 1600 °C

Abstract

SiC was introduced to UO2 matrix by spark plasma sintering (SPS) to improve the thermal conductivity. The microstructure evolution and thermal physical properties up to 1600 °C were firstly reported. The grain growth and the formation of equiaxed grain structure were inhibited by the addition of SiC. The critical SPS sintering temperature, above which SiC was positive on improving thermal conductivity, was discovered to be 1300 °C. Two equations were proposed to calculate the thermal diffusivity and thermal conductivity of SiC/UO2 sintering at 1500 °C. Each percent of SiC fraction brought about 3% increment in thermal conductivity. The coefficient of thermal expansion (CTE) was decreased after SiC addition. Such improvement in thermal conductivity and decrease in CTE were beneficial to the fuel safety in accident condition.