A charged topic: application of electrokinetic remediation for removal of difficult-to-measure radionuclides at nuclear sites

Abstract

As the number of nuclear sites across the world requiring decommissioning increases, so do the challenges faced by site operators whilst safely dismantling facilities. One common issue are difficult-to-measure radionuclides (DTMRs), which emit pure alpha, pure beta, low-energy gamma, or a combination of these radiation types during decay. This makes their in situ detection problematic, requiring complex analysis in laboratories to quantify activities present. DTMRs can be abundant at nuclear sites and so effective remediation technologies are essential for meeting both small-scale and site-wide decommissioning objectives. Whilst numerous decontamination techniques are currently deployed at nuclear facilities, the context specific nature of many remedial challenges mean that no single approach is appropriate for every scenario. Electrokinetic remediation (EKR) is a more sustainable and lower-cost decontamination technology compared to traditional approaches. A low-voltage direct current is applied to a contaminated material, inducing electromigration (movement of ions), electrophoresis (movement of charged colloids) and electroosmosis (movement of water). Whilst previous EKR work has focussed on easy-to-measure radionuclides (ETMRs), much less attention has been paid to DTMR remediation.
This thesis explores the applications of EKR on DTMRs, some for the first time in this context, that are present within materials commonly found at nuclear sites – namely, groundwaters, cements (as part of concretes), and sediments. H-3, Sr-90, and Tc-99 all showed good EKR amenability in groundwaters, although transportation rates varied between each. For both homogeneous- and surface-contaminated cements, Cs-137 displayed clear migration whilst H-3, Sr-90, I-129, and U-236 showing a lesser degree or no mobilisation. In an aged, authentically contaminated coastal sediment core, Tc-99 and Pu showed greater remediation capability with a citric acid electrolyte, with Am-241 more mobile with seawater and Cs-137 demonstrating little or no remobility in either setting. Overall, low-voltage EKR showed the greatest potential when treating environmental materials (i.e. groundwaters and sediments), with a trade-off existing between the voltage used and both the remedial project duration and financial cost. The time between contamination and treatment of the material is also shown to be important, highlighting the potential of EKR as an effective emergency response technology for radionuclide leaks. Future work should look at in situ applications of the technique as well as larger pilot-scale trials to further promote EKR use as a diverse remedial tool at nuclear sites.

More information

Identifiers

ORCID for Shaun Daniel Hemming: orcid.org/0000-0001-5826-8710

ORCID for Andy Cundy: orcid.org/0000-0003-4368-2569

ORCID for Phillip Warwick: orcid.org/0000-0001-8774-5125

Catalogue record

Export record