The influence of the fission product element Y on the oxidation process of UO2

To study the impact of fission product elements on spent nuclear fuel during high-temperature oxidation, this study selected yttrium (Y) as a representative element. UO 2 pellets doped with varying mass fractions of Y 2 O 3 (1, 3, and 5 wt%) were fabricated via high-temperature sintering. The results indicate that both the lattice parameter and grain size decreased with increasing dopant concentration, while the oxidation temperature increased significantly. Characterization of the oxidation products demonstrated a gradual reduction in U 3 O 8 content and a decrease in the average valence state of uranium ions as the Y 2 O 3 content increased. Kinetic analysis indicated an increase in the activation energy for UO 2 oxidation from 88.32 ± 2.21 kJ/mol (pure UO 2 ) to 122.27 ± 3.05 kJ/mol (5 wt% Y 2 O 3 - doped sample), confirming that Y 2 O 3 doping elevates the energy barrier for oxidation. This work provides critical data and a theoretical foundation for understanding the behavior of spent fuel containing rare earth fission products during oxidative volatilization, thereby offering valuable insights for optimizing spent fuel reprocessing strategies.