Irradiation behavior of the interaction product of U-Mo fuel particle dispersion in an Al matrix

Irradiation performance of U-Mo fuel particles dispersed in Al matrix is stable in terms of fuel swelling and is suitable for the conversion of research and test reactors from highly enriched uranium (HEU) to low enriched uranium (LEU). However, tests of the fuel at high temperatures and high burnups revealed obstacles caused by the interaction layers forming between the fuel particle and matrix. In some cases, fission gas filled pores grow and interconnect in the interdiffusion layer resulting in fuel plate failure. Postirradiation observations are made to examine the behavior of the interdiffusion layers. The interdiffusion layers show a fluid-like behavior characteristic of amorphous materials. In the amorphous interdiffusion layers, fission gas diffusivity is high and the material viscosity is low so that the fission gas pores readily form and grow. Based on the observations, a pore formation mechanism is proposed and potential remedies to suppress the pore growth are also introduced.

► We in-pile tested U-Mo dispersion in Al matrix.
► We observed interaction layer growth between U-Mo and Al and pore formation there.
► Pores degrades thermal conductivity and structural integrity of the fueled zone.
► The amorphous behavior of interaction layers is thought to be the main reason for unstable large pore growth.
► A mechanism for pore formation and possible remedy to prevent it are proposed.