Within the United Kingdom (UK) , it is proposed that nuclear waste will be disposed in a geological disposal facility, 200 m to 1 km underground1. This facility will incorporate an engineered barrier system that will be optimised to physically and chemically impede the transport of radionuclides to the biosphere. The facility will house a large volume of cemented Intermediate Level Waste (ILW), in addition to vitrified ILW. A significant volume of concrete will be used in its construction. Interaction of groundwater with the cementitious components of the facility (both the waste and construction materials) will lead to the presence of high pH conditions within a repository. The effect of cement leachates on vitrified wasteforms is not well understood.
We present results from a glass durability study using idealised cement leachates to develop our understanding of glass durability mechanisms in these complex repository like environments. Simulant ILW glasses relevant to the UK disposal program have been utilised. We also investigated a simulant UK high level waste glass (MW-25%) and the International Simple Glass2 (ISG), a 6 component borosilicate glass, with components that are common to most borosilicate nuclear glasses. Glass powders were exposed to idealised cement leachates of “intermediate” and “old” ages, approximately representative of GDF conditions at ~1000 and ~10,000 years of operation, according to the product consistency test B3. Analysis of the normalised mass loss and normalised leaching rate of these glasses as a function of cement leachate composition was achieved through analysis of solution concentrations. Simultaneously we present analysis of monolith sample alteration layers by SEM/EDX and GA-XRD. Collectively, these data support a mechanistic understanding of glass dissolution in the context of a complex geological disposal environment for vitrified UK waste