Thermal Transport in Thorium Dioxide

Abstract

Thorium is more abundant in nature than uranium and thorium fuels can breed fissile U-233 fuel that can be used in various types of nuclear reactors. Moreover, thorium dioxide has drawn interest from researchers due to its relatively superior thermal properties when compared to conventional uranium dioxide fuel pellets. In this study, thermal transport in thorium dioxide is investigated using reverse non-equilibrium molecular dynamics. The thermal conductivity of bulk thorium dioxide was measured to be 20.8 W/m-K and the phonon mean free path was estimated to be between 7 ∼ 8.5 nm at 300 K. It was also observed that the thermal conductivity of thorium dioxide has a strong dependency on temperature; the thermal conductivity decreases with an increase in the temperature. Moreover, by simulating thorium dioxide structures with different lengths at different temperatures, it was also identified that short wavelength phonons dominate thermal transport in thorium dioxide at high temperatures, resulting in decreased intrinsic phonon mean free paths and minimal effect of boundary scattering while long wavelength phonons dominate the thermal transport in thorium dioxide at low temperatures.