Kr implantation into heavy ion irradiated monolithic U–Mo/Al systems: SIMS and SEM investigations

Abstract

Worldwide, high performance research and material test reactors are aiming to convert their fuel from high enriched uranium towards low enriched ones. High density U–Mo/Al based nuclear fuels are considered as a promising candidate for this conversion. However, during in-pile test irradiations, the formation of an interdiffusion layer (IDL) between the U–Mo and the Al matrix is observed, caused by irradiation enhanced U–Al interdiffusion processes. This IDL accumulates fission gases at the IDL/matrix interfaces. Together, these two effects strongly reduce the performance of this new fuel type. Recently, the out-of-pile technique of heavy ion irradiation (127I) on U–Mo/Al layer systems proved to be an alternative to time-consuming in-pile test irradiations for certain fuel behaviour aspects. Here we present SIMS and SEM investigations of non-conventional 82Kr implantation into previously heavy ion irradiated U–Mo/Al layer systems. It is shown that Kr accumulates inside μm large porosities at the IDL/matrix interfaces. This critical accumulation of μm-sized large gas bubbles is directly related to the presence of the irradiation induced IDL. Without IDL no critical accumulation of fission gas bubbles occurs.