The Immobilisation Science Laboratory, University of Sheffield, is working with Magnox South Ltd to develop a range of glass formulations that are suitable for vitrification of the Wet Intermediate Level Waste (WILW) envelope arising from decommissioning of the Hinkley Point ‘A’ (HPA) power station. Four waste mixtures or permutations are under consideration for volume reduction and immobilisation by vitrification. The inorganic fractions of several of the wastes are suitable for vitrification as they largely consist of SiO2, MgO, Fe2O3, Na2O, Al2O3 and CaO. However, difficulties may arise from the high organic and sulphurous contents of certain waste streams, particularly spent ion exchange (IEX) resins. IEX resin wastes may be the key factor in limiting waste loading, and possible thermal pretreatments of IEX resin to decrease C and S contents prior to vitrification have been investigated. Our results suggest that lowtemperature (90 °C) pretreatment is more favourable than hightemperature (250, 450, 1000 °C) pretreatment. A thorough desktop study has provided initial candidate glass compositions which have been downselected on the basis of glass forming ability, melting temperature, viscosity, liquidus temperature, chemical durability and potential sulphate capacity. Early results for two of the candidate glass formulations indicate that formation of an amorphous product with at least 35 wt % (dry waste) loading is achievable for HPA IEX resin wastes.
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