- The legacy ponds research reduced radioactivity within the effluent treatment system by more than 69% and led to an estimated cost saving of more than £10 million.
- Microbial growth research directly informed in-pond treatment settings, enhancing fuel retrieval operations and saving approximately £2.4 million.
- Research into iron oxide floc formation and binding with radionuclides informed operational changes that further reduced radionuclide discharges to the Irish Sea.
Decommissioning high-hazard radioactive waste
The Sellafield site in Cumbria, UK is one of the most complex nuclear facilities in the world. Its legacy facilities contain high-hazard, spent nuclear fuel, some of which has corroded during storage in ponds to form sludge.
As a result, the facilities are described as posing an ‘intolerable risk’ by the Nuclear Decommissioning Authority – their safe and timely decommissioning is of national and international importance. In addition, radioactive liquid wastes that are also produced on-site require treatment before their disposal.
Professor Katherine Morris
Katherine Morris is Professor of Environmental Radiochemistry and Environment and Waste Lead at Dalton Nuclear Institute.
Understanding the behaviour of Sellafield's liquid waste treatment systems
The University of Manchester worked in collaboration with Sellafield Ltd and the National Nuclear Laboratory to explore radionuclide, mineral, and microbial behaviour in the pond environments, and radionuclide and mineral behaviour during effluent treatment processes, which use iron oxides to treat acidic, radioactive liquid wastes. The research findings were shared between industry and academic partners, enabling Sellafield Ltd to improve efficiency and safety.
Improving processes across the waste lifecycle
By applying the research findings Sellafield Ltd has further:
- improved liquid waste treatment;
- optimised storage and handling protocols;
- increased productivity and site safety.
The research and its impact cover three main areas of waste retrievals, handling and processing.
Sellafield’s legacy ponds – large deep reservoirs containing corroded spent nuclear fuel – are high-hazard environments: the removal and storage of their contents is a top priority to reduce risk on site. Some legacy ponds are susceptible to the growth of microorganisms, which can cause extensive ‘blooms’ that reduce visibility within the ponds and hinder the removal of the irradiated fuel waste.
University researchers studied these microorganisms and identified the species in the ponds responsible for the loss in visibility. As a result, Sellafield were able to apply and refine a range of strategies to inhibit their growth.
By limiting the microbial growth, visibility has improved in the ponds, allowing for a 40% increase in waste retrieval operations and accelerating risk reduction as the hazardous materials are removed and stabilised. These improvements have led to an estimated saving of at least £2.4 million in operational costs.
“It is crucial that this waste is retrieved as quickly as possible. Thanks to evidence-based changes in process, fundamentally underpinned by The University of Manchester's research, delays in waste treatment have been avoided.”
Senior Research Manager, Sellafield
Optimising waste handling
When pond retrievals occur, there is a period of settling before the overlying liquid wastes are separated from the radioactive solids and processed. The liquid wastes are stored in an effluent collection vessel in which the radioactivity in the solution increases over time until it challenges the operational capability of the treatment system.
University research insights informed new vessel mixing regimes, which made the liquid less cloudy, reduced the overall radioactivity in the effluent by between 69–95% and further reduced the likelihood of costly interruptions to retrievals.
Optimising waste processing
Another key treatment process at the site involves treating acidic radioactive liquid wastes that contain both iron and radioactivity. On treatment, the iron forms solid iron oxides (rust-like phases) which adsorb radioactivity dissolved in the liquid waste and precipitate out to form a ‘floc’. Filtration of this iron oxide floc leaves a cleaned liquid phase.
Research on how the iron oxides formed during the treatment process directly informed operational changes that improved the cleaning process. This operational change delivered a range of environmental and economic benefits, including further reducing the already low levels of actinide (long lived, high-hazard components of the releases) discharged into the Irish Sea by up to 90%.
Overall, this body of research has informed plant-level operations used in the decommissioning of key nuclear fuel storage ponds and liquid waste treatment systems at Sellafield – a top priority for the reduction of risk on site.
Collaborate with our experts
The Dalton Nuclear Institute acts as a central hub for nuclear energy research and development, providing advice and partnerships support to varied industry and academic collaborations.
Professor Francis Livens
Professor of Radiochemistry and Director of the Dalton Nuclear Institute
Professor Sam Shaw
Professor of Environmental Mineralogy
Professor Jon Lloyd
Professor of Geomicrobiology
Professor Scott Heath
Professor of Nuclear Chemistry
Dr Tom Neill
Research Fellow in Environmental Radioactivity
Dr Lynn Foster
Research Fellow in Geomicrobiology