Development of U-Zr-Xe ternary interatomic potentials appropriate for simulation of defect and Xe behaviors in U-Zr system

Abstract

U-10Zr metallic fuel (alloys of U with 10 wt% Zr) is considered as a potential candidate for fast reactors due to its excellent performance. However, the fission gas swelling has a significant impact on its properties and prevents it from reaching higher burnup. To gain a deeper understanding of the fission gas swelling mechanism, molecular dynamics simulations based on interatomic potentials are underway to fill the key knowledge gaps. In this work, two modified embedded-atom method (MEAM) potentials are developed for the U-Zr system with Xe, one for α-U-Zr and δ-UZr2, and the other for γ-U-Zr. The parameters of the potentials are determined by fitting the material properties from experiments or density functional theory (DFT) calculations. It is verified that the potentials can reproduce well the lattice constants, elastic constants, point defects, surface energy, and the melting point of U. In addition, the lattice constants, elastic constants, cohesive energy, and point defect formation energy of Zr are in good agreement with the experimental and DFT results. For the alloy system, the typical defect properties of Zr and Xe in U, as well as the formation energy and elastic constant of δ-UZr2 are close to the DFT. The lattice constant, linear thermal expansion, and mixing enthalpy of γ-U-Zr alloy are following the experimental values. The results show that the obtained potentials are suitable for simulating the defect evolution and Xe behaviors in the U-Zr system.