HADES: A User Facility for High Activity Decommissioning Engineering Science

HM Government's civil nuclear energy policy has the threefold objectives of: exploiting nuclear power for low carbon, reliable and affordable electricity generation; decommissioning the legacy of historic nuclear fuel cycle activities; and safe disposal of radioactive wastes. Building on the Nuclear Industrial Strategy, the Nuclear Sector Deal set the vision for the civil nuclear sector, to deliver by 2030:
* 30% cost reduction in cost of new build projects
* Savings of 20% in cost of decommissioning compared with current estimates
* Up to £2bn domestic and international contract wins
The HADES Facility for High Active Decommissioning Engineering Science aims to play a pivotal role in realisation of these objectives through investment of a suite of equipment to enable fundamental and applied research in thermal treatment of radioactive wastes. Such technology utilises the application of heat to immobilise radionuclides and chemotoxic species within a passively safe product (a glass, slag or ceramic) suitable for interim storage and disposal. The benefits afforded by this approach are potentially game changing and include radical volume reduction and elimination of waste reactivity and organic inventory. The estimated lifecycle cost savings arising from successful implementation of thermal treatment technology in legacy nuclear decommissioning programmes are £billions in each of the UK and USA. Thermal treatment of radioactive wastes from future advanced recycle of nuclear fuels will reduce the environmental footprint of future nuclear generation, and reduce the associated waste management cost, through development of next generation materials for high level waste immobilisation, which are compatible with the challenging characteristics of such wastes and achieve a greater efficiency of waste incorporation. The technological developments achieved in these domains will realise new intellectual property and highly skilled human capital to grow the UK share of the legacy and future nuclear decommissioning market.
The HADES Facility, the only one of its kind in the UK, will enable this impact to be realised by creating unique infrastructure to handle large radioactive inventories and real radioactive wastes at the laboratory scale, to develop waveform formulation, process envelope, and product disposability to advance thermal treatment technology and enable timely implementation by current and future site licence companies. In so doing, we will nucleate grow a world leading community of practice, producing highly skilled user-researchers, through effective training and networking activities. Additionally, the unique capability established within the HADES Facility will be a beacon to attract and engage international collaboration, enabling us to pool research resources to address trans-national challenges in radioactive waste management and extending the reach of impact from the arising research beyond the UK.

The HADES Facility will be unique in the UK with its capability to enable thermal treatment research with high inventories of radionuclides. The Facility will be capable of addressing a diverse range radioactive waste management challenges relevant to decommissioning of UK and international nuclear sites. In summary, we therefore focus on three areas of immediate impact, each associated with a Sheffield led research projects with EPSRC and industrial support, although we have identified a considerable UK and international user base who could exploit the facility capability to advance their own research programmes.
1) Maturation of hot isostatic pressing technology to immobilise UK plutonium stockpile and residues and high dose spent adsorbents. HM Government has placed renewed focus on management of the plutonium stockpile, for which immobilisation of at least 5tHM is likely to be required. Upgrade of our existing Hot Isostatic Press with an Active Furnace Isolation Chamber and control system, will allow systematic investigation of ceramic and glass-ceramic formulations utilising U and effective Pu surrogate and optimisation of process envelopes. Translation of the research outcomes enabled by the Facility infrastructure, through effective collaboration with the National Nuclear Laboratory, Sellafield Ltd., and Nuclear Decommissioning Authority, will contribute to the evidence base required to inform HM Government decision on plutonium immobilisation and an investment in a waste treatment complex. This research, which cannot currently be undertaken at any other UK facility, is timely and has the potential to address one of the highest priority challenges on the Sellafield site, from the perspective of both research outcomes and the operational experience of radiological HIP application. This work is supported by several EPSRC grant
2) Thermal treatment is one potential treatment option for spent ion exchange resins which pose a challenge to low level waste disposal, for example, due to incorporated complexants (e.g. EDTA). We are developing proof of the efficacy of thermal treatment to such wastes, which results in destruction of the complexant species and incorporation of the radionuclide inventory into a compatible glass matrix. The proposed equipment investment will support future laboratory scale development of this approach utilising real radioactive resin wastes supplied by MOD, to understand the impact of radiolytic degradation of resin on the process envelope, evolved off gas, and product quality. MOD, are undertaking a Best Practicable Environmental Option assessment for these wastes, to reduce onsite hazard in line with regulator advice. Thus, our planned research, enabled by the Facility, will be opportune because the outcomes will arise during a key window of strategy development to allow uptake by MOD to refine their waste management strategy and potentially open the first route for vitrified resin disposal at LLWR. The research outcomes will also be of interest to other waste producers.
3) The NDA Research Board has highlighted the need to "ensure that thermally treated products meet the acceptability criteria for disposal" as being of "fundamental importance" so that "disposability does not become a "show stopper" at a late stage". The RWM Science & Technology Plan specifies the knowledge gaps that need to be addressed in this regard, which focus on understanding the mechanisms of plutonium (glass)-ceramics and vitrified ILW glass dissolution, and interaction with engineered back fill materials, in conceptual disposal concepts; note, also there still remain knowledge gaps concerning the fundamental mechanisms of HLW glass corrosion. The proposed equipment investment will enable the UK research community to address these challenges by enabling preparation and characterisation of conceptual wasteforms, incorporating key radioactive elements (U, Tc), for mechanistic dissolution studies.