UK Dalton Institute looks at ways to manage plutonium

7 September 2023

The UK-based Dalton Nuclear Institute at the University of Manchester looking at whether the UK plutonium stockpile should become waste or energy. “Managing the UK plutonium stockpile: no easy choices”, examines the key things that government must consider when making that choice.

Over the last six decades, the UK has built up a stockpile of some 140 tonnes of civil plutonium, currently stored as plutonium dioxide powder at the Sellafield site. The 46-page study notes that the facilities, packaging and conditions of this storage are currently the subject of a Nuclear Decommissioning Authority (NDA) improvement programme over the next several decades. After the period of storage, the end point of the plutonium is being examined against the possible futures of conversion into either fuel for nuclear reactors or a waste-form for disposal in the planned UK Geological Disposal Facility (GDF).

In his Foreword to the study, Professor Clint Sharrad, Dalton Nuclear Institute says the plutonium could simply be used as fuel for existing or future thermal reactors. Also, it could be used to kickstart the process of utilising the UK's 100,000-tonne supply of Depleted, Natural and Low-Enriched Uranium (DNLEU) in fast reactors, which could power the UK for centuries. There may even be applications in future fusion reactors.

Currently NDA is repackaging the plutonium stocks into more robust containment. Future studies may show that extracting the energy from the plutonium is unnecessarily expensive, and that it might be simpler and cheaper to consider it a waste material to be managed accordingly.

The stockpile originates from reprocessing used fuel from the UK's reactor fleets, as well as some imported material. While the earliest application of plutonium was its use in weapons, most of the UK’s stockpile was produced only for civil purposes. In fact, the UK's civil plutonium stockpile is the largest in the world. “So there are some decisions to be made. Some need to be made soon, whereas others can, and should, be safely postponed until we have the necessary supporting information,” says Sharrad. “Delaying a decision does not remove the responsibility associated with it. A concerted and immediate effort to fill these information gaps is needed to put the UK in the best position possible to make the right decision on the right timescale.” The purpose of the Dalton study is paper to assist decision-makers in this matter. “To paraphrase the common saying about building new nuclear reactors, the best time to begin such conversations is around 20 years ago – but the second-best time is now!”

Overall, the message from this study is that the current storage improvement programme is an essential first step. This will allow the time for a properly resourced process to examine the ultimate fate of the plutonium stockpile on the basis of a balanced assessment of all aspects of the two alternative futures. Ten recommendations are presented along with a final, overarching recommendation. These are:

  • Recommendation one: Before attempting to make and implement policy decisions, government should ensure that a national dialogue takes place allowing stakeholders from all sides to share their views. This must be more than either a “lip service” consultation with outcomes already decided or a polarised “black versus white” argument.
  • Recommendation two: The current programme of repackaging and storing the plutonium inventory in optimal conditions must be carried out by NDA and Sellafield Ltd to the currently programmed end point of 100-year design life storage. This provides sufficient time for the necessary comprehensive Research, Development & Innovation (RD&I) required to underpin the whole plutonium lifecycle to be carried out in parallel.
  • Recommendation three: Bringing the UK plutonium programme to a successful end will take several decades at least. Both Government and NDA should provide the commitment and resources needed to ensure continuity and development of capability over this timescale.
  • Recommendation four: Government should decide on and implement a preferred end point for the plutonium once a satisfactory assessment of options and their attributes is available, taking into account changes in storage environment and the hazard that plutonium presents.
  •  Recommendation five: Given the hazard represented by the plutonium stockpile and the long duration of plutonium storage, the storage infrastructure is critical to safety and security. Government, NDA and other stakeholders must ensure that sufficient attention and resources are devoted to long term care of these assets.
  • Recommendation six: The hazard represented by the plutonium stockpile would be greatly decreased by conversion from dispersible powder into a solid form, but the choice of form will determine which future option is to be followed. government should ensure that a comprehensive assessment is carried out on the attributes and costs of the range of options.
  • Recommendation seven: The different disposition options follow very different pathways. To underpin decision-making, government needs to develop a full understanding of the whole plutonium lifecycle for each pathway before committing to irrevocable decisions.
  • Recommendation eight: Because of the major uncertainties associated with the UK’s plutonium management programme, it is unwise to rely on discounted costs to evaluate the programme. In particular the assumption of cost decrease associated with discounting should not be used as a pretext to delay decision making and action.
  • Recommendation nine: The decades-long, highly challenging programme needed to address the challenges of the UK plutonium stockpile can only be delivered by an experienced community of practice. Government should ensure there is a sufficient supply of suitably qualified and experienced personnel to deliver the programme.
  • Recommendation ten: Government should ensure that a robust, long-term RD&I programme is in place to support selection and implementation of any plutonium management option.
  • Overarching Recommendation: Government, which is ultimately responsible for management of the UK’s plutonium stockpile, should acknowledge that this is an unavoidably complex, multigenerational undertaking, requiring ongoing stewardship prior to an irrevocable decision on the end point for the material, and should put in place suitable arrangements. There are significant major uncertainties which can only be managed through a long term, programmatic approach with continuity, flexibility, adaptability, underpinned by RD&I commensurate with the scale of the challenge.

In conclusion, the report notes that there is ample evidence that government has not, in recent decades, “rushed into the fray of policy and decision making regarding the future of the UK plutonium inventory”. It notes that there are several reasons for this:

  • Resources within Government have been very stretched over recent years and continue to be stretched.
  • Decisions around the future use and management of plutonium would ideally be made against a backdrop of clear understanding about future UK plans for nuclear new build (technology, timeframe, scale, fuel strategy, and so on). Such understanding has not yet been clarified, and there is a risk that decisions made now about the future of plutonium stocks could be regretted in the future once these plans take shape.
  • Timescales for the various options for managing the plutonium inventory are all many decades in duration, which creates a persuasive perception that important (and sometimes irrevocable) decisions are best delayed for a while until more information is available.
  • Other nuclear and energy agendas in the context of net zero are more eye-catching and easier to present in a mainly positive and media-friendly light.
  • Announcements about plutonium policy are likely to attract robust criticism and be misrepresented as either perpetuating risk or pre-judging policy decisions around future new build programmes.

“Acknowledgement that the future management of plutonium is an unavoidably complex, multi-generational undertaking, requiring ongoing stewardship prior to an irrevocable decision on the end point for the material would be an important first step in moving the situation forward,” the report says. “Equally, recognition of the significant major uncertainties inherent in any future strategy is vital, and so there is clear value in a long term, programmatic approach with continuity, flexibility and adaptability.”

Image (top): Flowchart showing the Dispose versus Use paths (courtesy of Dalton Nuclear Institute, University of Manchester)

Image (right): Plutonium storage at the Sellafield nuclear site (courtesy of Nuclear Decommissioning Authority)

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