Evidence of amorphous interdiffusion layer in heavy ion irradiated U-8wt%Mo/Al interfaces

U-Mo/Al based nuclear fuels are worldwide considered as the most promising high density fuel for the conversion of high flux research and test reactors from highly enriched uranium to lower enrichment. However in-pile growth of an amorphous interdiffusion layer at the U-Mo/Al interfaces strongly limits the performances of this fuel. Several in-pile tests have been performed to optimize the composition. In this paper, a breakthrough in simulating the U-8wt%Mo/Al behavior under out-of-pile irradiation is reported. It is shown that an amorphous U-8wt%Mo/Al interdiffusion layer (IDL) is obtained by heavy ion irradiation (¹²⁷I) in a U-Mo/Al diffusion couple under controlled temperature conditions. The properties of this IDL coincide with the results obtained from in-pile tests. This methodological work clearly indicates that heavy ion irradiations could be routinely applied for optimizing composition of U-Mo/Al nuclear fuels. In other words these out-of-pile tests using ion beams could become a representative, efficient and economic step before in-pile irradiation.