Abstract Scope |
Accident tolerant nuclear fuels are necessary to ensure the safety of nuclear power reactors. Cracking due to thermal gradients and mechanical stresses provide additional pathways for radionuclide release. Pellet cladding interaction in Zircaloy-clad fuel can result in diffusion of Zr into the fuel matrix and formation of solid solution (U,Zr)O2 phases, while extreme conditions in a reactor meltdown results in a wide range of (U,Zr)O2 (ss) and metallic (U,Zr) phases. In this work, UO2 and (U1-yZry)O2 (y=0.01-0.2) are examined using X-ray diffraction (XRD), Raman spectroscopy and electron backscatter diffraction (EBSD). Synchrotron XRD and high temperature Raman spectroscopy show a decrease in the onset temperature of thermal oxidation with the addition of Zr, most prominently with lower concentrations of Zr. EBSD shows a 10X reduction of grain size in (U0.8Zr0.2)O2 compared to undoped UO2, accompanied by a lesser degree of cracking after oxidation to U3O8. |