Theoretical study on the mechanical and thermal properties of uranium dioxide doped with lanthanide fission products

Abstract

The structural, mechanical and thermal properties of fuel materials going through fission process are prime concern in the context of safe nuclear reactor operations. The interaction of fission products with the nuclear fuel significantly changes the fuel performance. Understanding their impact on fuel behavior is very important for efficient reactor operations. For this purpose, the mechanical and thermal properties of Uranium dioxide (UO2) fuel in the presence of lanthanide (Ln) fission products are calculated using first principles based electronic structure calculations. The density functional theory (DFT) calculations employed here is improved for strongly correlated 5f electrons of uranium using Hubbard-U corrections. The elastic properties such as bulk modulus, Young's modulus, Poisson's ratio etc. are evaluated from optimized structures of UO2 and Ln-doped UO2. The results obtained match very well with available experimental observations. Further, the thermal properties like heat capacity and coefficient of thermal expansion are calculated using quasi-harmonic approximation from phonon frequencies obtained from density functional perturbation theory. The calculated thermal properties gave excellent agreement with trends reported in available experimental studies. Atomic scale simulations performed here provide insight to most relevant fuel properties which will be helpful in designing advanced fuel materials.