Thermal conductivities of irradiated UO2 and (U,Gd)O-2

The evaluation of thermal conductivity of irradiated fuel is very important since it directly affects the fuel operating temperature. The disk-shaped UO2 and UO2-10 wt%Gd2O3 samples were prepared and irradiated to about 4%FIM A to measure the thermal diffusivities by the laser flash method. The burnu p was almost uniform within each sample. The irradiation temperature was al most constant and uniform within each sample except the temperature escalat ion that occurred during the irradiation. The thermal conductivity, determi ned from the thermal diffusivity, density and specific heat capacity, decre ased by irradiation, while it partly recovered after the thermal diffusivit y measurement at temperatures up to about 1800 K. The thermal conductivity reduction attributable to the irradiation-induced point defects was small i n the samples which experienced higher temperature than 1273 K during the t emperature escalation. The present results were compared with the reported models. (C) 2001 Elsevier Science B.V. All rights reserved.