LAUSR

Abstract In the UK, the Waste Vitrification Plant (WVP) at Sellafield converts the highly active liquid (HAL) waste from the reprocessing of spent nuclear fuel into a glass wasteform suitable for long term storage and disposal. After the completion of reprocessing operations, the highly active liquor (HAL) storage tanks will be emptied and washed out to remove any accumulated solids. These solids are expected to contain high concentrations of molybdenum. Hence, a new glass formulation has been developed specifically for immobilisation of these waste streams. This ‘Ca/Zn’ glass allows for significantly higher waste loadings by the formation of CaMoO4 crystals when the Mo content exceeds its solubility limit in the glass. The product quality of the new Ca/Zn glass is currently undergoing validation, which includes measuring the chemical durability to demonstrate its suitability for long-term storage and disposal. Previous powder-based leach tests have indicated a very slow approach to the low residual dissolution rate regime in contrast to other HLW glasses. Hence, this study investigated the leaching of Ca/Zn glass powders in Si-saturated solutions at high surface area to volume ratios in order to probe the long-term dissolution rate.