Investigation of Iron Phosphate Glasses for the Immobilisation of Pyroprocessing Wastes

Potential future fuel cycles may produce used nuclear fuels (UNFs) that are incompatible with aqueous reprocessing routes such as PUREX or UREX. Consequently, alternative routes such as pyroprocessing have seen renewed interest. Pyroprocessing is an electrochemical process and uses a LiCl-KCl eutectic (LKE) to dissolve the UNF which is then refined by means of electrochemistry. U and Pu may be recovered but the salt becomes progressively enriched in fission products, reducing efficiency and necessitating regeneration or replacement of the eutectic. Waste streams with high LKE content are highly challenging due to their low solubility in glass and ceramic wasteforms, high temperature volatility and aqueous solubility. Iron phosphate glasses have been reported to have a relatively high tolerance to the incorporation of chloride. As such, this study presents conceptual iron phosphate glass wasteforms for the immobilisation of these high chloride wastes. These materials have been characterised by powder X-ray diffraction, scanning electron microscopy, X-ray absorption spectroscopy, Raman spectroscopy, Mössbauer spectroscopy and aqueous durability testing. Initial results indicate that these wasteforms possess useful properties and could contribute to a toolbox for the immobilisation of challenging pyroprocessing wastes.