Microstructure and thermophysical properties of Er2O3-doped UO2 ceramic pellets

Abstract

Increasing the initial enrichment of 235U to develop super high burnup fuels is one of the hopeful ways to enhance the economic benefit for nuclear power plants. Er2O3-doped UO2 ceramic pellets have been considered as a promising nuclear fuel for solving the initial reactivity control due to the desirable neutron absorption property of Er as the burnable poison. Microstructure and thermophysical properties of doped UO2 ceramics containing 0, 5, 10 and 15 wt% Er2O3 were systematically investigated. Results show that the lattice parameter of the doped UO2 ceramics linearly decreases as a function of the Er2O3 content and follows Vegard’s law, indicating the formation of a complete solid solution between the Er2O3 and UO2 up to 15 wt% of the Er2O3 content. The average grain size, as well as specific heat capacity and thermal expansion coefficient of doped UO2 ceramics were considerably increased by the addition of Er2O3, while the thermal conductivity decreases very clearly with the Er2O3 doping content. Meanwhile, the mechanisms of changing the microstructure and thermophysical properties of Er2O3-doped UO2 ceramics have been discussed, and especially, the effect of lattice defects such as substitutional atoms and oxygen vacancy on the thermal conductivity has been discussed quantitatively with a phonon scattering model.