Microstructure studies of interdiffusion behavior of U₃Si₂/Zircaloy-4 at 800 and 1000 °C

Fuel swelling during normal reactor operations could lead to unfavorable chemical interactions when in contact with its cladding. As new fuel types are developed, it is crucial to understand the interaction behavior between fuel and its cladding. Diffusion experiments between U₃Si₂ and Zricaloy-4 (Zry-4) were conducted at 800 and 1000 °C up to 100 h. The microstructure of pristine U₃Si₂ and U₃Si₂/Zry-4 interdiffusion products were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) equipped with an energy dispersive X-ray spectroscopy (EDS) system. The primary interdiffusion product observed at 800 °C is ZrSi₂, with secondary phases of U-Zr in the Zry-4, and Fe-Cr-W-Zr-Si phases at Zry-4/ZrSi₂ interface and Fe-Cr-U-Si phases at ZrSi₂/U-Si interface. The primary interdiffusion products at 1000 °C were Zr₂Si, U-Zr-Fe-Ni, U, U-Zr, and a low melting point phase U₆Fe.