Effect of Gd2O3 Dispersion on the Thermal Conductivity of UO2

10 wt% Gd2O3-dispersed UO2 pellets, in which Gd2O3 particles are dispersed in UO2 matrix, were prepared, and the thermal conductivity was investigated. The Gd2O3-dispersed UO2 pellets consisted of Gd2O3, UO2, and a Gd-U-O phase that was formed by diffusion of U ions into Gd2O3 particles during the sintering process. In addition, pores were mainly distributed at the boundary between the Gd2O3 particles and the UO2 matrix. The thermal conductivity of 10 wt% Gd2O3-dispersed UO2 decreased with temperature (5.8-2.7 W m-1K-1 from 300 to 1273 K) and was larger than that of (U,Gd)O2 solid solutions (3.8-2.6 W m-1K-1) with the same Gd2O3 content. The increase in the thermal conductivity by Gd2O3 dispersion was attributable to the reduction in phonon-point defect scattering in the UO2 matrix. Dispersion of Gd2O3 particles was effective in improving the thermal conductivity of Gd2O3-UO2 fuel pellets.