Diffusion studies of U-Zr alloys with Fe alloys at 650 C and 700 C - 5263

Diffusion studies of uranium-zirconium alloys with iron alloys are relevant in the developments of metallic nuclear fuels for fast neutron reactors. Metallic fuels have preferable qualities in reactors, such as the ability to reach higher burn-ups and be manufactured with available space to accommodate swelling from fission gases. Zirconium is commonly included in the fuel because it stabilizes the irradiation behavior of uranium and reduces fuel-clad interactions. It also has a small neutron capture cross-section. Earlier diffusion studies have reported the interactions of uranium and iron and uranium alloyed with zirconium and iron. In this work it is demonstrated that diffusion couples of both uranium and uranium-zirconium alloys with both iron and HT-9 stainless steel (12Cr-1MoVW) strongly interact, and both exhibit behaviors similar to uranium-iron diffusion. Additionally, there are new phases consistent with those found in the Fe-U-Zr ternary phase diagram, but chromium is not found in the interaction regions. Another key difference when uranium-zirconium is coupled with HT-9 is that the diffusion rates are much smaller. This result is interesting because it suggests an interaction between zirconium and chromium, despite a negligible rate of diffusion for chromium. Hence, diffusion experiments involving uranium and uranium-zirconium with chromium have also been performed and the results will be presented elsewhere. (authors)