Distillation of Components of the LiCl–KCl–LaCl3–CeCl3–NdCl3–UCl3 Molten Mixtures under Reduced Pressures

Data on the saturated vapor pressure and relative volatility of various individual chlorides (LiCl, KCl, NdCl3, CeCl3, LaCl3, and UCl3) involved in the pyrochemical processing of spent nuclear fuel (SNF) are briefly reviewed. Alkaline metal chlorides are shown to be most volatile. The volatility of rare-earth metal and uranium trichlorides in a temperature range of 500–1000°C is lower by 2–5 orders of magnitude. Components of molten chloride electrolytes based on a LiCl–KCl eutectic placed in nickel boats containing uranium and rare-earth metal trichlorides are subjected to high-temperature vacuum distillation under different conditions: temperature 700–1000°C, time 0.4–4 h, degree of vacuum from 2 × 10–3 to 2 Pa, and concentration 0.25–1.7 mol % UCl3 and 0.13–0.7 mol % rare-earth element (REE) trichlorides (totally). The redistribution of the salt components between the melt and vapor condensates is determined. The conclusions are made about the relative volatility of the components of the molten salt mixtures (alkaline metal, REE, and uranium chlorides), and optimum distillation conditions are chosen.