Abstract—The technology of pyrochemical processing of mixed nitride uranium–plutonium spent fuel that is applied at the experimental and demonstration energy complex of the Siberian Chemical Plant includes several certain procedures finally aimed at extraction of the target fission products. The penultimate stage of processing is planned to be the electrorefining of the products of the previous stage, namely, metallized spent nuclear fuel (SNF). To implement electrolytic refining, it is necessary to determine the processes and technological regimes of electrolytic refining of the alloys modeling the product of this stage at the processing module. The results of electrorefining of the model alloys (modeling raw materials of the electrorefining stage) on an enlarged laboratory electrolysis cell are presented. The initial parameters of uranium refining in the melts based on 3LiCl–2KCl–UCl3 have been determined earlier. The basic parameters of refining are the use of the 3LiCl–2KCl–UCl3 (10.1 wt % UCl3) electrolyte and conducting experiments at 550°C. The uranium alloys containing palladium and neodymium are prepared by direct melting of uranium metal, PdAP-1 palladium metallic powder, and neodymium metal (99.99%) in a medium of high-purity argon (99.998%). At 550°C, the cathodic deposits are typical dendritic forms of orthorhombic α-uranium tending to needle formation with an increase in the cathode current density. An increase in the process time and the cathode current density leads to a decrease in the current efficiency because of electrode short circuit caused by cathodic deposit needles or metal fell from the cathode. The conditions of the cathodic process are clarified as a result of electrorefining experiments. For the electrorefining of the alloys U–Pd (1.59 wt %), U–Pd (1.62 wt %), U–Pd (1.54 wt %), U–Pd (1.58 wt %)–Nd (5.64 wt %), U–Pd (1.84 wt %)–Nd (6.49 wt %), and U–Pd (1.79 wt %)–Nd (6.54 wt %), uranium cathodic deposits are produced. They are subjected to chemical analysis, which shows a high purity of the resulting metallic uranium and the absence of metallic palladium and molybdenum. The palladium and uranium separation factor exceeds 5000, and that of neodymium and uranium is higher than 1000, which corresponds to the requirements imposed on purification from fission products at this stage of pyrochemical processing of SNF. Palladium is accumulated in anodic tailings, while the major mass of neodymium dissolves in molten electrolyte.
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Nikitin, D.I., Polovov, I.B. & Rebrin, O.I. Electrorefining of Uranium Alloys Containing Palladium and Neodymium in 3LiCl–2KCl–UCl3 Melts. Russ. Metall. 2023, 1031–1039 (2023). https://doi.org/10.1134/S0036029523080177
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DOI: https://doi.org/10.1134/S0036029523080177