The Effects of Xe/Cs Occupation on the Thermal Transport Properties of U3si: A First-Principles Study

Abstract

In this study, the effects of fission products Xe and Cs on the thermal conductivity for U3Si, which has been proposed to be an alternative nuclear fuel for UO2 due to its high thermal conductivity and high uranium density, are systematically investigated based on first-principles calculations. It is shown that Xe/Cs occupation in U3Si results in degraded thermal transport properties, due to the weakened chemical bonding, decreased phonon group velocity, as well as destroyed periodic structures caused by Xe/Cs occupation. However, the thermal conductivity of 9.8 ~ 14.0 W/mK at 300 K and 12.9 ~ 29.6 W/mK at 1000 K for Xe/Cs-containing U3Si are remarkably larger than the respective values of 8.3 W/mK and 3.5 W/mK for ideal UO2. The presented results suggest that the U3Si with Xe/Cs occupation has better thermal transport ability than the traditional nuclear fuel UO2, particularly at high temperatures, demonstrating the great potential of U3Si as an Accident Tolerant Fuel.

Keywords: First-principles calculations, Uranium silicide compounds, Electron and phonon, Thermal transport properties