A STRUCTURAL-CHEMICAL APPROACH TO SELECTING CRYSTALLINE MATRICES FOR ACTINIDE IMMOBILIZATION

Abstract

The use of confinement matrices is a key part of safe management of high-level radioactive wastes (HLWs) derived in the nuclear fuel cycle. The matrices should immobilize radioisotopes after HLW deposition in the geological environment with possible groundwater filtration. The glasses currently used for this purpose on an industrial scale are not capable of incorporating sufficient amounts of plutonium and have low stability to chemical corrosion. This paper summarizes the results of structural analysis of crystalline phases that could be used for immobilization of actinide wastes of various compositions. It was suggested that pyrochlore-type phases can be used for incorporation of the actinide-zirconium-rare-earth element fraction of HLWs, while ferrites with a garnet structure could be used for immobilization of wastes of complex composition with high contents of corrosion products (Fe, Al, Ga). Ceramics of such composition were synthesized and analyzed for concentrations of actinides (Th, U), rare-earth elements (Gd, Ce), and Zr. It is necessary to study the stability of these phases to radiation and chemical corrosion to select suitable matrix materials.