Anisotropic thermophysical properties of U3Si2 fuel: An atomic scale study

Due to renewed interest in uranium silicide compounds as a candidate for nuclear reactor fuels, there is a need for extensive investigations of their thermophysical properties as a function of temperature. In this work, we calculate the thermophysical properties of the U3Si2 compound within the framework of molecular dynamics (MD) using a semi-empirical modified Embedded-Atom Method (MEAM) potential and density functional theory (DFT). Thermal expansion, thermal conductivity, heat capacity, and elastic properties are presented as a function of temperature from 300 to 1800 K. The thermal conductivity of U3Si2 increases with temperature due to the electronic contribution while the phonon contribution decreases with increasing temperature. The phonon contribution to the thermal conductivity at 300 K is estimated at 2.03 W/mK and 1.41 W/mK using non-equilibrium molecular dynamics (NEMD) and equilibrium molecular dynamics (EMD), respectively. The electronic contribution is estimated to be 8.56 W/mK using the semi-classical Boltzmann transport theory at 300 K. Furthermore, we compared the thermal conductivity in two different crystallographic directions to shed light on the spatial anisotropy using NEMD and EMD methods. The inherent anisotropic thermophysical properties can be used to parametrize phase field models to incorporate anisotropic thermal conductivity and thermal expansion, allowing for a more accurate description of microstructural evolution under variable temperature and irradiation conditions. (c) 2019 Elsevier B.V. All rights reserved.