Orthophosphates of Langbeinite Structure for Immobilization of Alkali Metal Cations of Salt Wastes from Pyrochemical Processes

Mixtures of alkali metal chlorides used as electrolytes in pyrochemical processes for nuclear fuel production and spent nuclear fuel reprocessing were subjected to conversion into orthophosphate ceramic materials based on langbeinite mineral. The results of the solid-state synthesis of the phosphates are described. The phase and chemical composition, chemical stability, and heat resistance of the orthophosphates were studied by X-ray phase analysis, X-ray spectrum microanalysis, emission spectrum analysis, and scanning electron microscopy. Quantitative incorporation of alkali metal cations, including Cs, into such materials was proved. The use of a binder (89% Bi2O3 + 11% NaF mixture) considerably increases the density of the ceramic prepared and substantially enhances its chemical stability.