Using carbonate ions to investigate Ce(III) ions precipitation in molten chlorides (NaCl-KCl)

This study focuses on the oxidation of Ce(III) ions into cerium dioxide (CeO 2 ) as a surrogate of Pu(III) ions in NaCl-KCl eutectic (50.6-49.4 mol%) molten salt at 700°C. The oxidation was achieved through carbonate ions addition in the context of plutonium recycling. This process is designed for salt recycling in the context of MSR (Molten Salt Reactor) or actinide pyroprocessing. The behaviour of sodium carbonate (Na 2 CO 3 ) in this salt, mainly the CO 3 2- ion, was investigated using Differential Scanning Calorimetry (DSC) and infrared spectroscopy. These analyses revealed the high solubility and stability of carbonate ions in this salt, as well as its enhanced stability over extended usage periods. Several CeCl 3 /Na 2 CO 3 ratios have been studied to realize the oxidation, and the isolated powders were analyzed using different characterization methods including XRD (X-Ray Diffraction). Cerium chloride conversion yield has been determined around 99.99% using elementary methods. The analysis showed that the precipitates contained a mixture of CeOCl/CeO 2 with a molar ratio of less than one of Na 2 CO 3 and only CeO 2 with an excess of Na 2 CO 3 . The exact amount of Na 2 CO 3 required was determined by elucidating the reaction mechanism via gas analysis.