MBase: The Molecular Basis of Advanced Nuclear Fuel Separations

Over 95% of used nuclear fuel is uranium and plutonium, which can be recovered and reused. However, because used fuel is intensely radioactive, this requires very complex processes. These processes can also be adapted to the separation of high hazard materials from the residual radioactive wastes, to simplify radioactive waste management. However, industrial reprocessing of used fuel primarily relies on a 50 year old solvent extraction process (Purex), which was originally developed for much simpler fuels. As a result, modern fuels can prove difficult to reprocess. We will therefore explore two different approaches to nuclear fuel separation in parallel, one based on the established Purex technology and the other on a much more recent development, ion selective membranes (ISMs). ISMs are porous, chemically reactive membranes which can bind metals from solutions then release them again, depending on conditions, thus allowing highly selective separations.In the solvent extraction system, we will focus on a common problem in solvent extraction, third phase formation, and on separation of a group of long lived, high hazard waste isotopes (the fission product technetium and the minor actinides). With the ISMs, we will first prove their utility in uranium/plutonium separation, then extend these studies to the minor actinides. Throughout, we will work with the elements of interest, rather than analogues or low activity models and in realistic radiation environments. In both strands of the project, we will explore the underlying physical and chemical processes then, building on this understanding, we will develop a series of quantitative models, building from phase behaviour to unit operations and finally to process flowsheet models. We wil use the resulting models to explore different options for fuel reprocessing, based on scenarios defined with our industrial partners.

Beneficiaries The main direct beneficiaries of knowledge and outputs arising from this research will be: - The National Nuclear Laboratory (NNL), responsible for supporting the UK's strategic nuclear R&D and for preserving and developing specialised high level skills. - Idaho National Laboratory (USA) is the US Department of Energy's lead National Laboratory for fuel cycle R&D, aiming particularly to deliver a step change in the nuclear fuel cycle. - The Nuclear Decommissioning Authority (NDA), which is responsible for all of the UK's civil Licensed Nuclear Sites, and Sellafield Ltd (SL), one of the NDA Site License Companies. Sellafield Ltd is responsible for the UK's only operating Purex separation plants, one for metal fuel and one for LWR oxide fuel, and current plans project continuation of reprocessing until at least 2016. - The Health and Safety Executive Nuclear Directorate (ND), which has the statutory responsibility to regulate all Nuclear Licensed Sites. ND and its predecessor, NII, have long promoted skills development in the nuclear sector, an important aim of the MBase consortium. - The UK National Nuclear Centre of Excellence (NNCE) is being set up in response to a recent policy announcement (The Road to 2010) to enhance the UK's work on and capability in non-proliferation. - Government Departments (DECC and Defra), which are responsible for developing policy for the civil nuclear sector. Engagement Mechanisms Consortium Membership. Both NNL and INL are full partners in the consortium, with Serco Assurance participating in the criticality studies. Annual MBase Conference. All consortium members will meet for an annual conference, where key research results, developments and advances will be communicated across the whole consortium and to a wide range of external stakeholders. Public Communication. We will coordinate our activities in this area with the Nuclear FiRST DTC, led by the CRR in Manchester (PI Livens), which is developing an active programme of public engagement. These includes a series of 'Caf Scientifique' events to engage the public, workshop events, participation in the EPSRC Impact programme, and a programme of Schools visits. Web-based Communication. A website detailing the consortium activities and linking to all consortium members will be set up for access by anyone with an interest in the research and its outputs. This will be interactive, featuring for example, a message board for comment and questions, and will also be used to disseminate background information on the scientific context in which the consortium is working (e.g. proliferation-resistance; partitioning as a waste management option; potential for recycling of future fuels).