Electrokinetic Remediation for Nuclear Site Decommissioning (RSC Radiochemistry YRM2021)

Electrokinetic Remediation, EKR, is an electrochemical remediation technology that uses electricity to remove pollutants, such as fission products (137Cs, 90Sr), actinides (U-Am) and other radioactive and non-radioactive species, from contaminated nuclear site materials. It is a flexible and low-energy (< 1 V.cm-1) technique that operates effectively in low permeability substrates (cements, etc.) which are difficult to remediate by conventionally (e.g. chemical oxidation). It can be combined with renewable power inputs and operate in-situ, providing effective, safe, and sustainable solutions in which worker exposure to hazardous radiochemicals is minimized while high remediation efficiencies are retained. However, EKR is limited mostly to the laboratory or pilot scale for nuclear industry applications, with reliable, meter-plus scale studies in real operating environments still lacking. Figure 1 – The EKR process, with precipitation of iron-rich phases shown when electrodes used are steel. Cation (C+) and anion (A–) movement with pH gradient, towards electrodes of opposing charge, is shown. Water electrolysis half-cell values are vs. SHE. Here, we discuss EKR and its potential uses at nuclear sites at scale. We begin by summarizing the key advantages offered by EKR over other, conventional remediation methods and, from this, review how EKR, singly or in combination with other technologies, can be or has been applied practically. We also discuss our recent efforts (e.g. analysis by XRD, SEM/EDX, - and Mossbauer spectroscopies, etc.) to understand how a model system, using electrochemically precipitated Fe (Figure 1), influences sorption of selected contaminants in real nuclear materials. The target audience for this contribution cross-cuts academia and industry, developing fundamental concepts (electrochemistry, geochemistry) and applying them to the grand challenge of tackling the UK’s nuclear waste legacy