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

According to the Nuclear Decommissioning Authority, Higher Activity Waste (HAW) includes High
Level Waste (HLW), Intermediate Level Waste and some Low Level Waste that is unsuitable for
disposal in the Low Level Waste Repository. HLW from re-processing typically occurs in liquid form
and is converted into a solid product via a process called 'vitrification' prior to long-term storage and
disposal. Storage is via canisters placed into an air-cooled store until a suitable disposal route
becomes available. A facility would store vitrified HLW for at least 50 years before disposal. The UK
Government's policy for long-term management of HAW is geological disposal, which involves
placing waste deep underground in a Geological Disposal Facility (GDF). A GDF includes multiple
engineered barriers, several hundred metres underground, constructed in a suitable geological
environment to ensure that the radioactivity in the waste is sufficiently isolated and contained that
it 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 site
selection process to find a volunteer host community with suitable geology. The Welsh Government
has also decided to adopt a policy of geological disposal for the long-term management of HAW and
continues to support the policy of voluntary engagement. Scottish Government policy is that the
long-term management of HAW should be in retrievable near-surface facilities close to the origin of
the waste.
The temperature of HLW can rise significantly because of its radioactivity. This poses technical
challenges when designing a GDF, due to the impact that the released thermal energy could have on
the physical and chemical stability of both natural and engineered barriers, with potential
consequences for the GDF's long-term safety and reliability. If the original structure of the rock is
altered, for example, it may change a groundwater movement pattern and the transport pathway
for 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 GDF
via bespoke, closed-loop geothermal energy recovery systems, where the HAW would act as a hightemperature anthropogenic geothermal source. Geothermal engineering design concepts will be
developed and evaluated for potential GDF application taking account of depth, layout, geological
characteristics at the site, the radioactivity inventory and the anticipated temperature field
development over time. Their impact on the long-term integrity of GDFs will be assessed, as will the
amounts of recoverable energy for heat and/or power generation or for use to maintain stable
repository conditions, taking account of safety, operational and environmental constraints.
The project provides an ideal opportunity for a highly motivated geoscientist, physical scientist, or
engineer to develop solutions to important problems affecting energy and the environment. The
studentship will benefit from the doctoral training opportunities of the Graduate School of the
college of science and Engineering in Glasgow University. The work will be conducted in the School
of Engineering in Glasgow, in collaboration with the Scottish Universities Environmental Research
Centre in East Kilbride.