Electrokinetic Separation for Enhanced Decontamination of Soils and Groundwater Systems

Safely managing the legacy of first generation nuclear power, reducing nuclear risks and hazards, has in recent years become a priority for the nuclear industry both in the UK and Republic of Korea (ROK) as downscaling continues in the interim to 'new nuclear'. The Nuclear Decommissioning Authority (NDA, UK) estimate the total cost of decommissioning first generation nuclear power to be £121 B over the next 120 years, with significant costs associated to the management of spent fuel and legacy wastes. However, substantial effort is also directed towards remediating sites prior to their next planned use.

Remediating soils and groundwater is extremely challenging due to the low-levels of radionuclide contaminants encountered in the environment and their strong association with clays, rendering simple washing of contaminated soils inadequate. The challenge to successfully remediate is pointedly highlighted by the vast quantities of soils which have now been removed and stored at interim facilities following the incident at the Fukushima Daiichi Nuclear Power Plant. Substantial disturbance to the ecosystem is discouraged and methods to remediate soils and groundwater in-situ are highly favored.

The proposed research will consider in-situ remediation by chemical-enhanced electrokinetic separation to desorb Cs and Sr from difficult clay types. Chemical treatment using non-ionic, biodegradable polymers will be explored as a method to expand clay interlayers and recover ions which have become 'trapped' in clay particles. Once desorbed the mobile ions should be recovered to prevent their migration. Our partners at KAIST, ROK will design novel adsorbents to isolate ions at the cathode via electrochemical separation and by adsorption using 2D fabricated composite membranes that are impermeable to the selected ions to deliver rapid sorption kinetics and high adsorption capacity.

The research will advance understanding on appropriate methods to desorb ions from different clay types and successfully capture mobile ions, locally concentrating the contaminants and reducing the volume of waste for ultimate disposal. As decommissioning programs advance, remediation of soils and groundwater systems will come into focus. Installing in-situ technologies which can achieve high decontamination levels, require minimal engineering support, and do not cause long-term damage to the local ecosystem are highly desired and have the potential to accelerate remediation timescales and reduce the full lifetime costs of decommissioning legacy nuclear sites.

Finally, the UK-ROK international collaboration and industry partnership has an opportunity to enhance public confidence in the nuclear sector, engaging with future engineers and the general public who will witness a nuclear sector moving away from 'care and maintenance' to actively returning legacy sites to their desired end-state, all at the same time as growing 'new nuclear' and moving waste to its ultimate destination in a geological disposal facility.

With the recent publishing of the ROK 'Energy Conversion Roadmap' and announcement of downscaling of nuclear power plants in the ROK from 24 to 14 by 2038, waste management and decommissioning programs have become a priority for both the UK and ROK. In the UK alone, clean-up of 17 of the UK's earliest nuclear sites (operated by four site licence companies (SLCs) i) Sellafield Ltd., ii) Magnox Ltd., iii) Low Level Waste Repository Ltd., and Dounreay Site Restoration Ltd.) is estimated to cost £121 B over the next 120 years (NDA), with land remediation (soil and groundwater), one of the four major activities supporting decommissioning, estimated to cost £3 B. Innovation that can deliver substantial cost savings is highly desired and is now a recognized driver for the UK nuclear decommissioning sector; "...innovation-led growth that delivers successively lower generation costs and a 20 per cent reduction in decommissioning costs to the taxpayer" (Industrial Strategy Nuclear Sector Deal, 2018).

Planning for site remediation is currently ongoing with the likely commencement of land remediation strategies/techniques to be mid-to-late 2020s (Sellafield), hence the nature of the proposed fundamental research is very timely. Sellafield Ltd. (project partner - see supporting letter) recently completed (2002-2010) an extensive contaminated land and groundwater management project (presentation Cruickshank, 2012) to assess the levels of contamination resulting from "a number of leaks, spills and burials". The results from the study highlighted major contaminants including 137Cs and 90Sr, and the potential for over 13 M m3 of soil classed as radioactive waste.

In-situ remediation by chemical-enhanced electrokinetic separation is a mostly passive treatment process of relative low cost (compared to direct disposal) and minimal impact to site operations, attributes of significant benefit when initiating remediation projects on congested sites around buildings with vibration constraints.

Research successes will be shared via a number of industry-focused forums including i) Sellafield Ltd. working groups, ii) EPSRC TRANSCEND (see supporting letter) theme and annual meetings with industry participation from SLCs, NNL, AWE, TUV SUD, Cavendish Nuclear, NDA, RWM Ltd., iii) the Nuclear Waste and Decommissioning Research Forum with industry participation from (duplicates not included) EDF Energy, MoD, Government Decontamination Services, Culham Centre for Fusion Energy, and iv) CL:AIRE (Contaminated Land: Applications in Real Environments) a not-for-profit organization to stimulate the regeneration of contaminated land in the UK by sharing best practice and knowledge. Our project partners SNC Lavalin / Atkins and Sellafield Ltd. are both members of this group and will facilitate engagement throughout the project.

Our industry partner SNC Lavalin / Atkins is a global engineering company developing innovative solutions to address customer issues across the nuclear lifecycle. With vast experience providing the highest performing nuclide abatement systems at Fukushima, Japan, along with suppling systems for new build Chinese LWR reactors, CANDU reactors, a tritium processing facility, and solid and liquid waste managment systems to Korean LWRs, SNC Lavalin / Atkins is a highly valued partner who can directly benefit from the proposed fundamental research, furthermore creating opportunity to advance the technology/methods up the technology readiness levels. SNC Lavalin / Atkins is also known for their excellence in nuclear waste management at numerous sites across the US, Europe and the Middle East, hence the two-strands of research being proposed are of direct relevance to SNC Lavalin / Atkins.