Effect of Melt Composition on the Reaction of Uranium Dioxide with Hydrogen Chloride in Molten Alkali Chlorides

The reaction of uranium dioxide with excess hydrogen chloride in alkali chloride melts (LiCl, 3LiCl-2KCl, NaCl-KCl and NaCl-2CsCl) has been studied between 450 and 750 ◦ C, and the reaction products were characterized by electronic absorption and X-ray absorption spectroscopy. Uranium( V), [UO 2 Cl 4 ] 3− , and uranium(IV), [UCl 6 ] 2− , species were formed. They depended upon the temperature and the radius of the alkali cations present. Uranium(V) ions predominated in melts with small cations (LiCl and 3LiCl-2KCl).