Microstructural characteristics of plasma sprayed, electroplated, and co-rolled Zr diffusion barriers in hot isostatic pressed low enriched U-10 wt% Mo monolithic fuel plates

Microstructural development in U-10 wt% Mo monolithic fuel plates with Zr diffusion barriers applied by electroplating, plasma spraying and co-rolling was examined after hot-isostatic pressing in Aluminum alloy, AA6061 cladding. Scanning and transmission electron microscopy were employed to examine the phase constituents and microstructure of the fuel alloy, Zr diffusion barrier, and the interaction between them. The co-rolled Zr barrier exhibited the most uniform thickness and a least amount of defects (e.g., porosity, inclusions and delamination). However chemical banding was observed within the fuel alloy. The electroplated Zr diffusion barriers were inconsistent in thickness, contained a significant amount of the δ-ZrH_1.5 phase, and yielded inconsistent interdiffusion and reaction with the U–10Mo fuel alloy. The plasma sprayed Zr diffusion barriers contained a significant amount of porosity, exhibited inconsistent barrier thickness, and produced a UO₂ layer, 2–3 μm in thickness due to interdiffusion and reaction with the U–10Mo fuel alloy during HIP.