Polarizable force field parameterization and theoretical simulations of ThCl₄ -LiCl molten salts

Recycle of thorium is an essential process in the thorium-uranium closed fuel cycle of molten salt reactor (MSR). Pyrochemical treatment of spent nuclear fuel using chloride molten salts as medium has been considered as a promising method. In this article, we performed molecular dynamics simulations on the ThCl₄ LiCl molten salts using a polarizable force field parameterized by us from first-principles calculations. The microscopic structures and macroscopic properties at different compositions were investigated using the developed force field to understand the structure/property relationship in the mixture. The differences between ThCl₄ LiCl and ThF₄ LiF MSs are compared to understand the behaviors of Th⁴⁺ in the fluoride-chloride mixed media. In the molten fluorides, the coordination number of Th⁴⁺ is larger, and the resulting more shared anions lead to lower ThF dissociation barrier and shorter lifetime of the Th⁴⁺ first solvation shell. Our results also indicate the Pauling's structural rules for crystals can be used to rationalize the local structures in molten salts. © 2018 Wiley Periodicals, Inc.