Modeling the phase diagram of U-Zr-Ce metallic fuel and calculating solubility limit of Ce in U and Zr by using first principles and phonon calculations

Abstract

During irradiation, rare earth elements (REEs) tend to be redistributed to the outer region of fuel along the temperature gradient. The migration of REEs lead to the fuel-cladding chemical interaction which causes fuel failure. Accurate phase diagrams of U-Zr-REEs and U-TRU-Zr-REEs are needed to analyze this phenomenon. However, existing phase diagrams are calculated based on insufficient experimental data particularly. In this study, the solubility limits of $\gamma$-Ce in $\alpha$-U and $\alpha$-Zr are calculated by using first principles and phonon calculations based on density functional theory (DFT) to improve the binary phase diagrams of Ce-U and Ce-Zr. From these calculation results, binary phase diagrams of Ce-U and Ce-Zr were calculated and compared with existing literature data. The ternary phase diagram of the U-Zr-Ce is modeled by extrapolations of new binary phase diagrams obtained from the calculations.