Improving the safety and reliability of geological disposal of higher activity radioactive waste via geothermal energy co-production

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According to the Nuclear Decommissioning Authority, Higher Activity Waste (HAW) includes HighLevel Waste (HLW), Intermediate Level Waste and some Low Level Waste that is unsuitable fordisposal in the Low Level Waste Repository. HLW from re-processing typically occurs in liquid formand is converted into a solid product via a process called 'vitrification' prior to long-term storage anddisposal. Storage is via canisters placed into an air-cooled store until a suitable disposal routebecomes available. A facility would store vitrified HLW for at least 50 years before disposal. The UKGovernment's policy for long-term management of HAW is geological disposal, which involvesplacing waste deep underground in a Geological Disposal Facility (GDF). A GDF includes multipleengineered barriers, several hundred metres underground, constructed in a suitable geologicalenvironment to ensure that the radioactivity in the waste is sufficiently isolated and contained thatit will not cause harm to people and the environment for many hundreds of thousands of years.There is currently no GDF operating in the UK, but the Government is currently developing a siteselection process to find a volunteer host community with suitable geology. The Welsh Governmenthas also decided to adopt a policy of geological disposal for the long-term management of HAW andcontinues to support the policy of voluntary engagement. Scottish Government policy is that thelong-term management of HAW should be in retrievable near-surface facilities close to the origin ofthe waste.The temperature of HLW can rise significantly because of its radioactivity. This poses technicalchallenges when designing a GDF, due to the impact that the released thermal energy could have onthe physical and chemical stability of both natural and engineered barriers, with potentialconsequences for the GDF's long-term safety and reliability. If the original structure of the rock isaltered, for example, it may change a groundwater movement pattern and the transport pathwayfor radionuclides to the environment. Also, waste glass could undergo devitrification.This project aims to investigate the potential benefits of controlling the temperature field in a GDFvia bespoke, closed-loop geothermal energy recovery systems, where the HAW would act as a hightemperature anthropogenic geothermal source. Geothermal engineering design concepts will bedeveloped and evaluated for potential GDF application taking account of depth, layout, geologicalcharacteristics at the site, the radioactivity inventory and the anticipated temperature fielddevelopment over time. Their impact on the long-term integrity of GDFs will be assessed, as will theamounts of recoverable energy for heat and/or power generation or for use to maintain stablerepository conditions, taking account of safety, operational and environmental constraints.The project provides an ideal opportunity for a highly motivated geoscientist, physical scientist, orengineer to develop solutions to important problems affecting energy and the environment. Thestudentship will benefit from the doctoral training opportunities of the Graduate School of thecollege of science and Engineering in Glasgow University. The work will be conducted in the Schoolof Engineering in Glasgow, in collaboration with the Scottish Universities Environmental ResearchCentre in East Kilbride.