Microstructure evolution and phase transformation of heavy-ion irradiated U–Mo/Al fuels

The microstructure evolution and phase transformation of the interdiffusion layer resulting from the interaction between U–Mo and Al in U–Mo/Al bilayer systems irradiated from 140 °C to 275 °C are discussed. Heavy ion irradiation was used as a convenient tool to produce an interdiffusion layer comparable to those occurring during in-pile irradiation. A burn-up equivalent of up to ∼7.7×10²⁰f/cm³ has been reached to simulate the early in-pile irradiation. Scanning and transmission electron microscopy coupled with energy dispersive spectroscopy were performed to determine the phase and the composition of the induced interdiffusion layer. The present analysis reveals that the U–Mo/Al interdiffusion layer is completely amorphous up to an irradiation temperature of 200 °C. In our experimental geometry, nanograins start to form from 220 °C, propagating from the Al layer towards the U–Mo layer. The γ-U-Mo and the Al layers retain their crystallinity. Furthermore, with increasing irradiation temperature, the Al proportion in the interdiffusion layer rises, indicating an enhanced Al atomic flow with increasing irradiation temperature.