Characterisation and disposability assessment of multi-waste stream in-container vitrified products for higher activity radioactive waste

[Display omitted] •In-container vitrification (ICV) is assessed for thermal treatment of nuclear waste.•UK specific wastes were blended with glass forming additives (e.g. soil) by ICV.•The vitrified products were variably heterogeneous in nature.•Low release rates for radionuclide surrogates during aqueous leaching were achieved.•Products performed similar to or better than HLW glass acceptable for disposal. Materials from GeoMelt® In-Container Vitrification (ICV)™ of simulant UK nuclear wastes were characterised to understand the partitioning of elements, including inactive surrogates for radionuclide species of interest, within the heterogeneous products. Aqueous durability analysis was performed to assess the potential disposability of the resulting wasteforms. The vitrification trial aimed to immobilise a variety of simulant legacy waste streams representative of decommissioning operations in the UK, including plutonium contaminated material, Magnox sludges and ion-exchange materials, which were vitrified upon the addition of glass forming additives. Two trials with different wastes were characterised, with the resultant vitreous wasteforms comprising olivine and pyroxene crystalline minerals within glassy matrices. Plutonium surrogate elements were immobilised within the glassy fraction rather than partitioning into crystalline phases. All vitrified products exhibited comparable or improved durability to existing UK high level waste vitrified nuclear wasteforms over a 28 day period.