Chlorination of Li₂O and uranium metal in molten LiCl-KCl using NH₄Cl

This paper reports on a new approach to chlorinating molten salts using vaporized NH₄Cl. In separate experiments, chlorination of dissolved Li₂O and submerged U metal was demonstrated. Ammonium chloride was thermally decomposed in a quartz glass vaporization chamber with an internal temperature ranging from 295 to 384 °C. These decomposition products were then bubbled into eutectic LiCl-KCl salt via argon carrier gas. The vapor appears to absorb as NH₄⁺/Cl^- into the molten LiCl-KCl based on the high dissolved concentration of acid compared literature reported solubility of HCl. In Li₂O chlorination experiments, complete reaction was achieved starting with 1 wt% Li₂O for reaction times of 24.8 h or less. In U metal chlorination experiments, dissolved U concentrations ranged from 1.75 to 4.17 wt% for reaction times ranging from 3.5 to 21.6 h. The rate limiting step is mass transfer and reaction between the molten salt and U metal pellet. Cyclic voltammetry peak heights were correlated with dissolved U concentration with overall scan results consistent with UCl₃ being the dominant form of dissolved U. (author)