Solubility and dissolution kinetics of uranium trifluoride in 2LiF-BeF2 molten salt

Although uranium trifluoride (UF 3 ) holds promise for applications in molten salt reactors, its high-temperature physicochemical properties in molten salt systems have yet to be thoroughly explored. In this study, the solubility and dissolution kinetics of UF 3 in molten 2LiF-BeF 2 (66–34 mol %, FLiBe) eutectic salt were investigated using the isothermal saturation method within the temperature range of 823 K to 973 K. High-purity UF 3 compacts (∼99.70 %) were synthesized via an optimized solid-phase reaction protocol and subsequent compacting. The UF 3 -saturated FLiBe molten salts were prepared by immerse dissolution of nickel mesh-wrapped UF 3 compacts and bulk uranium in the molten salt, eliminating the filtration step. Experimental findings showed that the dissolution equilibrium of UF 3 in the FLiBe salt was 120 h. The solubility of UF 3 exhibited a linear increase (R 2 > 0.99) from 4.16 wt. % to 12.60 wt. % as the elevation of temperature. Crystallographic analysis confirmed that the typical UF 3 phase was the only uranium-bearing phase throughout the dissolution process, while deconvolution X-ray photoelectron spectroscopy (XPS) verified the exclusive presence of the U 3+ species under all temperature conditions. Notably, the dissolution kinetics conformed to a mass transport control model.