Uranium chemical species in LiCl-KCl eutectic under different conditions for the dissolution of U3O8

Abstract As a typical uranium oxide, the electrochemical behaviors of U3O8 in molten salt have attracted many research endeavors, but its dissolution behavior and related mechanism in molten salt has been less well understood. In this work, we reported the dissolution of U3O8 in LiCl-KCl eutectic with the assistance of NH4Cl, which has potential significance for the pyrochemical reprocessing of spent oxide fuels. The spectroscopic techniques such as fluorescence emission spectroscopy, UV-Vis absorption spectroscopy, and X-ray Absorption Fine Structure (XAFS) were used to determine the chemical species during the dissolution process of U3O8. The results show that U3O8 can be completely dissolved in molten salt under the air atmosphere, and it exists in the form of [UO2Cl4]2−. In contrast, under an argon atmosphere, the soluble [UO2Cl4]3− and insoluble UO2 were detected as the main products.