Electrochemical Separation of Alkaline-Earth Elements from Molten Salts Using Liquid Metal Electrodes
Thomas P. Nigl, Timothy Lichtenstein, Yuran Kong, Hojong Kim
Abstract
Closing the nuclear fuel cycle requires recycling used nuclear fuel. Additional waste is generated during recycling due to fission products accumulating in processing salts (LiCl–KCl). Reducing the waste generated during recycling entails recovering alkaline-earth fission products (Ba2+/Sr2+) from molten chlorides with a minimal loss of bulk electrolyte constituents (Li+/K+). Electrochemical codeposition of Ba2+/Li+ and Sr2+/Li+ into liquid metal (Bi, Sb, Sn, and Pb) and alloy (Bi–Sb) electrodes was investigated in LiCl–KCl–(BaCl2, SrCl2) electrolytes at 500 and 650 °C. For the pure Bi (500 °C) and Sb (650 °C) electrodes, the greatest percentage of charge was used to deposit Ba and Sr. Effective recovery of Ba/Sr by liquid Bi and Sb electrodes is supported via experimentally determined activity values of Ba/Sr in Bi and Sb. Alloying Sb with Bi increased Ba recovery but decreased Sr recovery, compared to the recovery using a liquid Bi electrode. The results suggest that alkaline-earth fission products can be recovered from molten chlorides using liquid metal electrodes via electrochemical separation, thereby providing a method to reduce the generation of nuclear waste from nuclear fuel recycling.