THERMAL-CONDUCTIVITY MEASUREMENTS ON UO2+X FROM 300 TO 1,400 K

In order to evaluate the thermal conductivity of oxidized fuel pellets of leaker fuel rods, UO2+z samples with x between 0.00 and 0.20 were prepared by an oxidation or a sintering method. Sample thermal diffusi vities were measured by using a laser flash method from 300 to 1,400 K and their thermal conductivities were evaluated from multiplying the thermal diffusivities by the sample densities and the specific heat ca pacities derived from the literature. The thermal conductivities of UO 2+x were decreased with increasing hyperstoichiometry and they were ex pressed as a function of their hyperstoichiometry using the concentrat ion of U5+ formed with the excess interstitial oxygen atoms.