DAWNMANTLE - Decontamination and waste minimisation strategies for and using advanced molten salt nuclear technologies

Molten salt reactors and pyroprocessing technologies are likely to be key components in future nuclear fuel cycles. The attraction of these technologies can be argued is predominantly based upon the inherent safety imparted by the use of molten salt media (e.g. reduced criticality risk allowing small plant footprints; reduced likelihood of volatile radioactive species formation compared to oxide fuel reactors; plant operation at atmospheric pressures; negligible radiation degradation of molten salt media). These technologies also have the potential to be applied to current and near future decommissioning programmes such as decontaminating materials and minimizing waste volumes requiring managed disposal. Contaminated metals make up a significant proportion of the waste inventory as components (such as pipework, vessels and structural beams etc.) become contaminated during nuclear operations. In 2016, the Nuclear Decommissioning Authority reported that there is approximately 32,000 tonnes of contaminated intermediate level waste (ILW) stainless steel in the UK alone. At a current predicted rate of ~£70,000/m3 to dispose of ILW, this volume of waste adds up to a considerable cost liability.
This project aims to assess materials requirements that will allow the deployment of advanced molten salt technologies in current decommissioning programmes and across various operations in future nuclear fuel cycles, and determine whether these technologies can provide benefit the nuclear energy sector. This will be achieved by a cradle-to-grave approach by assessing the nature of all materials that come in contact with radioactive material with these approaches and attempting to provide safe and effective waste management options for all waste streams.

The key impacts from this proposed research are as follows:
- Development of molten salt technologies for decontaminating problematic steel materials from nuclear processes for reclassification to lower waste categories as part of an integrated waste management strategy.
- Materials performance assessments linked with decommissioning requirements providing comprehensive selection criteria to determine material type/s for structural containment of molten salt technologies in nuclear processes.
- Contribute to databases of spectroscopic and electrochemical information of various species (e.g. radioelements, corrosion products) in molten salt media that can be used to assess the chemical composition within these extreme environments - for immediate use by the academic community for the verification of molten salt studies, but can be used in future processes to determine salt compositions from on-line process monitoring data.
- Journal and conference publications will be submitted from this work with each output mainly focussing on the sharing of fundamental data and understanding typically related to an individual operation.