ENCAPSULATION OF WASTE

摘要

The invention relates to a ceramic material for the encapsulation of high level radioactive waste, e.g. resulting from the reprocessing of irradiated nuclear fuel. Waste streams which are likely to arise in the future due to developments to the so-called PUREX process (so-called Advanced PUREX process) may not be suitable for containment by the established vitrification technique. The invention provides a ceramic waste immobilising medium in which waste from reprocessed nuclear fuel assemblies is contained and in which waste ions from at least fission products in irradiated nuclear fuel may be dissolved in substantially solid solution form, the ceramic waste immobilising medium having a matrix comprising phases of hollandite, perovskite and zirconolite in which matrix said waste ions are dissolved, wherein the waste comprises significant amounts of material from non-fuel components of fuel assemblies. Also provided is a method of immobilizing waste from reprocessed nuclear fuel assemblies, the method comprising the steps of mixing a liquor containing said waste with a precursor material comprising oxides or oxide precursors of at least titanium, calcium and barium to form a slurry; drying said slurry; and calcining said dried slurry under a reducing atmosphere to form a powder, the powder comprising 30-65 weight % waste.