Thermal Conductivity of PuO₂ as Determined from Thermal Diffusivity Measurements

The thermal conductivity of PuO₂ as determined by thermal diffusivity measurements is presented for the temperature range 250 to ≈1200°C. Specimens of PuO₂ with confirmed stoichiometry were fabricated by hot isostatic pressing of powder to densities of 96.5 and 81.9% of theoretical. The thermal diffusivity of four specimens, two of each density, was measured by the heat pulse technique using a laser as the heat source. The data indicated that the thermal conductivity of PuO₂ is lower than that of UO₂, and decreases with increasing temperature from 250 to 1000°C in an approximate 1/T relation. Values range from 0.06 W/(cm deg C) at 300°C to 0.025 W/(cm deg C) at 1200°C. An apparent reduction of the PuO₂ was observed at temperatures above 1200°C.