High level waste (HLW) partitioning concept includes separation of a long-lived fraction following by its immobilization in ceramics. Improved process flow sheet suggested for implementation at PA 'Mayak' implies production of a long-lived HLW fraction with rare earth elements (REE) as major components, Am and Cm as minor constituents, and only traces of U, Pu, and corrosion products (iron group elements). Because most of the elements occurred are trivalent, one of the most promising host phase is supposed to be REE aluminate or ferrate with perovskite structure. Major advantages of the perovskite are incorporation of trivalent REEs and actinides, simultaneous incorporation of residual corrosion products, flexibility of perovskite structure allowing accommodation of traces of tetravalent actinides (U, Pu), high chemical durability, and high HLW volume reduction. High melting points of the perovskites makes problematic melting route, therefore, cold pressing and sintering method is more preferable. In order to reduce sintering temperature pre-treatment of ceramic batches with high mechanical energy has been studied.
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