Development of monazite glass-ceramic wasteforms for the immobilisation of pyroprocessing wastes

Pyrochemical reprocessing is a potential route for the reprocessing of fuels from next-generation reactors. Lanthanide fission products may be separated from the reprocessing salt by a number of methods; however, salts may be entrained in the resultant product. This work demonstrates conceptual monazite glass-ceramic wasteforms based on the quarternary (100−x)(10Na2O–36Fe2O3–54P2O5)–xLa2O3 (x = 5, 10, 15), with La2O3 as a surrogate for the lanthanide oxide waste stream. Samples were produced by the melting of La2O3 with a sodium-iron-phosphate glass frit and characterised by XRD and SEM–EDX. The monazite phase was successfully formed at all waste loadings with clear segregation of La to the crystalline phase; however, high La2O3 loading (>10 mol%) was found to destabilise the glass system resulting in gross crystallisation. These initial results indicate that monazite glass-ceramics are promising wasteforms for this waste stream.