As the UK prepares to invest in new operational nuclear power plants, industry and research organisations are also looking to decommission the UK’s existing nuclear legacy facilities. Fuel cladding, and corrosion products thereof, represent one of the major challenges to waste retrievals and storage at Sellafield and the wider nuclear industry. Waste is currently housed in aged storage facilities pressing retrieval and interim storage (such as the Magnox Swarf Storage Siloes) prior to immobilisation and geological storage. The volume and porosity changes arising are complex, and overall porosity increase and volume expansion have only been observed in unconfined cases, where reaction rates are appreciable.
This PhD project will work alongside leading teams within the University of Leeds and Sellafield Ltd, to investigate the nature of waste evolution under storage conditions in order to predict volume changes and resulting forces generated on confinement packaging. Specifically, under interim storage, Magnox alloy undergoes a series of physical and chemical changes; such as corrosion reactions forming brucite, as well as with CO2 to form hydromagnesite and other magnesium hydroxycarbonate phases as a soil/clay like sediment bed, which will gradually dry-out over long timescales. Behaviour under confined conditions and over the timescales of storage (many decades) is poorly understood, resulting in significant costs to the UK taxpayer to ensure wastes are safely stored. This is an exciting interdisciplinary project, combining chemistry and civil engineering with soil mechanics and geotechnics. It will also involve a close working relationship with the nuclear industry.