Enhanced Electrochemical Oxidative Decontamination
Large amounts of infrastructure from the UK civil nuclear programme are to be decommissioned over the next 50+ years. The whole of the NDA estate (reactor stations and reprocessing facilities) contains significant quantities of pipework and vessels, all of which will require decontamination. Completing decontamination permits reclassification of wastes and provides more efficient use of repositories.
During the decommissioning process it is often desirable to remove surface contamination in order to reduce hazard and simplify further processing operations (e.g. providing man access for cutting and size reduction operations). Wet decontamination procedures and wash outs are commonly employed for this purpose, which generate large volumes of liquid effluent. As an example, for the Sellafield site alone it is conceivable that decontamination effluents could be in the order of between 50,000 and 100,000 m3. Management and disposal of effluent is therefore a limiting factor in deployment of wet decontamination processes.
In addition, the most effective decontamination solutions often contain combinations of acids (e.g. nitric/HCl) and complexants e.g. citric acid, EDTA. However, their application is often limited by downstream issues, like corrosiveness of halides, resulting in damages to downstream plants, and interference of complexants with downstream processing and containment of nuclear waste. Recovery or destruction of halides (e.g. chloride) and complexants to avoid these issues would allow potentially more aggressive decontamination solutions to be used, resulting in shorter clean up times.
The ELENDES project: pilot-scale EEOD developed with NNL
In response to these challenges C-Tech Innovation has developed the Enhanced Electrochemical Oxidative Decontamination (EEOD) process, which uses patented new types of electrode materials in conjunction with electrode configurations to effectively break down strong acid and complexant mixtures. The treated wastewater is then suitable for downstream processing with existing plant.
The advantages of EEOD include:
- Capability to effectively treat strong acid / complexant mixtures resulting in faster, simpler lower cost downstream waste processing
- The opportunity to employ more effective decontamination reagents that may otherwise be discounted due to issues with downstream processing through the electrochemical removal of problematic components.
- The potential to treat isolated or otherwise inaccessible plant removing reliance on centralised infrastructure hence accelerating decommissioning timescales.
The EEOD process can lead to significant increases in effectiveness of decontamination effluents by allowing the innovative deployment of new decontamination solutions, and will therefore deliver improved efficiency, i.e. increased levels of decontamination, and cost reductions (e.g. through reclassification of nuclear waste). It will also open up the potential to treat isolated plant and to remove reliance on centralised infrastructure hence accelerating decommissioning timescales.
The application of electrochemical treatment of decontamination effluents can offer the opportunity to develop a remotely deployable decontamination process that can service the whole of the NDA estate and MOD and CBRN resilience. The technology could also have a role in supporting the maintenance requirements for nuclear reactor stations.