An ab-initio based semi-empirical thermal conductivity model for multiphase uranium-zirconium alloys

Abstract

In this work, a three-stage thermal conductivity model for complex metal alloys is developed, based on density functional theory (DFT) calculations, physics rules, and experimental data. The model is broken down into three stages for incorporating incremental complexity—Stage 1: modeling single-phase alloys with fixed compositions over a range of temperatures; Stage 2: modeling single-phase alloys across a range of compositions; and Stage 3: modeling multi-phase mixtures. The model is demonstrated using U-Zr and U-Mo alloys and displays good agreement with experimental data, with a root-mean-square error (RMSE) of about 1.3 W/m-K (~10% error against experimental data) over the typical operating temperature range for all phases of U-Zr. This model delivers the same level of accuracy as existing models for U-Zr and U-Mo, along with the same (or fewer) number of fitting parameters. More importantly, all the fitting parameters have clear physical meaning, providing significant insights into the physics of various electron- and phonon-scattering mechanisms and enabling predictions regarding the thermal conductivities in alloys, with a reduced reliance on experimental data.