COVER STORY | LEGACY POND TREATMENT
Right: Alkaline to neutral radioactive effluents from the highest nuclear risks and hazards at Sellafield – its legacy ponds and silos – are treated in the Site Ion Exchange Plant (SIXEP)
What is the process for deciding on what projects to
take forward? Morris says, “this is all about communication of challenges by the subject matter experts coupled to careful listening and refinement of research ideas across the Centre of Expertise, which has led us to define and refine successful projects together”. The group’s work was cited in the Research Excellence
Framework, the UK’s five yearly assessment of impact made by its higher education and research organisations. The Framework’s aims include providing accountability for public investment in research and produce evidence of the benefits of this investment; and to provide insights into the health of research in the UK’s higher education institutions. The citation is a testament to the impact of the E&DCE between September 2015 and July 2020. Its outcomes
included: ● Reducing radioactivity within the effluent treatment system at Sellafield’s legacy ponds by more than 69%, with an estimated cost saving of more than £10 million (US$12.6 million).
● Microbial growth research that informed in-pond treatment settings and enhanced fuel retrieval operations enabling a 40% increase in fuel retrieval operations, with savings of around £2 million (US$2.5 million).
● Research into iron oxide floc formation and binding with radionuclides, resulting in optimised treatment protocols for radioactive reprocessing effluents, allowing Sellafield to achieve a 50–90% reduction in actinide discharges during targeted periods of plant operations and significantly reducing alpha radioactivity discharges to the Irish Sea.
The challenge at Sellafield At the UK’s complex and challenging Sellafield site, operations and decommissioning are under way simultaneously. The work addressed two types of radioactive effluents that are generated on site. Firstly, acidic radioactive effluents, from reprocessing spent nuclear fuel and the subsequent clean-up of legacy reprocessing facilities, are treated in the enhanced actinide removal plant (EARP). Secondly, alkaline to neutral radioactive effluents from the highest nuclear risks and hazards at Sellafield – its legacy ponds and silos – are treated in the Site Ion Exchange Plant (SIXEP). Since 2013 a programme of research has covered three
areas: ● Iron oxide flocculation and radionuclide removal during reprocessing effluent treatment.
● The EARP process neutralises the acidic, radioactive effluents to form an iron floc that scavenges the radionuclides from solution. The treated aqueous effluent is then discharged to the environment under authorisation.
● Research on iron oxide floc formation pathways was developed and discussed with NNL and Sellafield.
Above: Acidic radioactive effluents are treated in the enhanced actinide removal plant (EARP) at Sellafield. An experimental EARP rig is shown
32 | March 2024 |
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University of Manchester research into the EARP floc formation pathway identified that, counter to classic nucleation models, Fe-13 Keggin moieties were present under very acidic conditions (pH <0.15). This highlighted that effluent streams in EARP with higher initial pH values may
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