Formation of Rare-Earth Element Phosphates in the Melts Based on the Equimolar Mixture of Sodium and Potassium Chlorides

The processes that occur during the reactions of 15 rare-earth element (yttrium, lanthanum, and all lanthanides except for promethium) chlorides with sodium orthophosphate in the melts based on the NaCl–KCl equimolar mixture are studied in an inert atmosphere at 750°C. The phase and granulometric compositions of the rare-earth element phosphates are determined. The influence of the molar ratio of phosphate to rare-earth element on the composition and particle size of the phosphates is studied. The conditions necessary for the quantitative precipitation of both individual rare-earth elements and a mixture of the rare-earth elements from the melt are determined. The mixture of rare-earth elements imitates the content of rare-earth fission products in the spent nuclear fuels to be processed.