Interaction Between Uranium Trifluoride and the Mixture of Lithium and Beryllium Fluorides

Abstract

Equilibrium potentials of uranium have been measured in the LiF-BeF2-UF3 melt as a function of temperature and uranium fluoride concentration. The empirical equation of uranium potential isotherms and polytherms have been obtained. Cathode polarization of uranium in the molten mixture of beryllium and lithium fluorides has been measured using the current switch off method from the stationary state. Uranium ions were found to have primarily the-valence of three in the LiF-BeF2 electrolyte in the studied temperature and uranium fluoride concentration ranges. Conditional standard potentials of uranium in the molten mixture of lithium and beryllium fluorides were calculated relative to the reference fluorine electrode according to the experimentally obtained data on the equilibrium potentials of the uranium electrode in the LiF-BeF2-UF3 melt. Standard conditional changes in the Gibbs energy, enthalpy, and entropy at the formation of uranium trifluoride from the elements in the form of dilute solutions were determined. The enthalpy of mixing of liquid uranium fluoride and the 0.73LiF – 0.27BeF2 melt was calculated.