Radiation driven diffusion in gamma U-Mo

A monolithic fuel design based on a U-Mo alloy has been selected as the fuel type for conversion of the U. S. High-Performance Research Reactors. A critical phenomenon of interest regarding U-Mo monolithic fuel is the large amount of swelling that takes place during operation, particularly at high fission densities. The accurate prediction of fuel evolution under irradiation requires implementation of correct thermodynamic and kinetic properties into mesoscale and engineering fuel performance modeling codes. One such property where there exists incomplete data is the diffusion of relevant species under irradiation. Fuel performance swelling predictions rely on an accurate representation of diffusion in order to determine the rate of fission gas swelling and the local microstructural evolution. In this work, we present molecular dynamics simulations of the radiation driven diffusion of U, Mo, and Xe in U-Mo nuclear fuels. Diffusion coefficients for each species are determined over a range of temperatures and compositions. Updated diffusion coefficients are presented that are applicable under irradiation and incorporate both intrinsic and radiation driven diffusion. (C) 2020 Elsevier B.V. All rights reserved.