Structure characterization and steam oxidation performance of U3Si2 with Zr alloying additions

Research and development of high uranium density fuels supports the on-going effort to enhance reactor technology, safety, performance, and economics. Among high uranium density fuels, U ₃Si ₂ is a favored fuel candidate due to its higher uranium density and improved thermal conductivity when compared to traditional UO ₂. While U ₃Si ₂ demonstrates an improved fuel economy, it suffers from rapid degradation when exposed to water at T > 300°C. In order for U ₃Si ₂ to be implemented in water cooled reactors, the water reaction must be understood and mitigated. Reported here is the performance of Zr alloying additions to U ₃Si ₂ exposed to high temperature steam oxidation environments. The investigation shows that homogenization heat treatment contributes to a delayed onset of oxidation and an improved homogeneity throughout the arc-melt fabricated alloyed compositions. Of the pre- and post-annealed samples, the post-annealed 7 vol% Zr addition exhibited the highest onset temperature of oxidation. A preliminary computational investigation to complement the experimental analysis assesses the solubility of Zr in U ₃Si ₂ and its incorporation in the crystal lattice.