Thermodynamic assessment of the uranium-zirconium alloy system for nuclear energy applications

Abstract

Uranium – 10 wt% zirconium (U-10Zr) alloy nuclear fuels have been used for many decades and new variations are under consideration ranging from U-5Zr to U-50Zr. The thermophysical behavior of the uranium-zirconium system has been revisited using differential scanning calorimetry (DSC) and other methods. Alloys containing 0.1, 2, 5, 10, 20, 30, and 50 wt% zirconium were prepared by melt-casting ~40 g samples in yttrium oxide crucibles. The phase transitions observed using DSC analyses are in general agreement with the established phase diagram with a few notable exceptions that may, in part, be due to impurities. Most notably, the transition from the α(U)+γ phase field to the β(U)+γ phase field at ~662°C was never observed in these experiments. This observation is consistent with earlier experimental assessments of the U-Zr binary phase diagram as compared with the more recent computational assessments.