First-principles molecular dynamics evaluation of the electroreduction kinetics of Nd from molten LiCl-KCl salt on different liquid metals

Abstract

Electrorefining has been identified as a promising technique for recovering valuable actinides from spent nuclear fuels. However, the electrochemical separation of accumulated fission products in the electrorefining salt electrolyte is a remaining challenge that is important for the minimization of the radioactive waste volume. In this work, we employed first-principles molecular dynamics (FPMD) simulations to investigate the performance of five candidate liquid metal electrodes (i.e., Bi, Pb, Sb, Sn, Zn) in separating Nd (a major fission product) from LiCl-KCl molten salt. The equilibrium potentials and diffusion coefficients of Nd³⁺ in these liquid metal cathodes are calculated via FPMD simulations and validated with literature data. The radial distribution functions, bond-angle distribution functions, Voronoi polyhedron and binding energies corresponding to the local Nd structure are analyzed to interpret the strong atomic interaction between Nd and the liquid metals. Finally, the calculated properties are incorporated into an electrode kinetics model to evaluate the electrolysis performance of different liquid metal cathodes, demonstrating the prospect of FPMD-based approach to streamline the selection of efficient electrode materials.