Effect of Nb On Sintering Process of Gamma Phase Uranium Alloys Fuel Pellets

Abstract

As a candidate material for metallic fuel, U-Mo metal fuel pellets are the most promising. U-Mo and U-Mo-Nb alloy pellets with a certain porosity were successfully prepared by the process of hydrogenation/dehydrogenation - compression molding - argon liquid-phase sintering. In order to study the effect of Nb addition on γ phase uranium alloy fuel pellets, microstructure and thermo-properties of the samples were observed by XRD/SEM etc. Results showed that with the increase of Nb content in the pellets from the non-add to micro-adding, Nb can facilitate the diffusion of Mo into the U matrix, resulting in the formation of a metastable γ-U phase. Meanwhile, during the same liquid phase sintering process of U-Mo fuel pellets, with the increase of Nb content, the number of secondary phases in U-Mo fuel pellets gradually decreased, while the size and number of voids of the secondary phases decreased. And the distribution of voids is more uniform. The specific heat capacity and thermal diffusivity of porous γ phase uranium alloys fuel pellets with different density were measured and thermal conductivity from 373K to 873K were calculated according to the experiment results. It is suggested that the thermal conductivity will increase with the density of pellets.