SOLVING THE Pu PROBLEM | WASTE MANAGEMENT


be reprocessed, though some fuel was reprocessed for commercial reasons. This programme coincided with the construction of the THermal Oxide Reprocessing Plant (THORP) that was commissioned in 1994. THORP’s principal mission was to reprocess fuel from the UK and also from foreign reactors and led to some foreign-owned plutonium remaining in the UK. While the intention was to eventually use the plutonium


for power generation in a future programme of fast reactors, the planned for the adoption of fast breeder reactors did not materialise. Fast reactors were presumed to be necessary because of an anticipated shortage of uranium. However, world nuclear programmes did not increase as quickly as had been thought, and the availability of uranium resources had also been very underestimated. As a result, the UK’s plutonium inventory has remained


stored as plutonium dioxide powder at Sellafield in the Northwest of the country for many decades. More recently, the drive to Net Zero and the necessary


low- carbon energy sources needed to achieve that could allow the UK’s plutonium stock to play a significant role in the national energy mix. Not only does plutonium offer primary generation opportunities, but it could also facilitate the huge energy potential of the UK’s stock of depleted uranium. The authors note that DU becomes a viable energy source in fast reactors fuelled with plutonium. As nuclear fuel, the amount of energy produced would vary with the reactors and fuel types used but could be very significant. Nonetheless, the authors also point to doubts on the economics of plutonium use as well as safety and security fears considering its continued storage. These issues could potentially drive options for its earliest possible disposal as waste, they say. “This choice is complicated by the fact that the


timescales of all the ‘Use’ or ‘Dispose’ options are dependent on construction and operation of new plants, and many also require the availability of the UK’s projected Geological Disposal Facility (GDF),” the report says. Indeed, these factors mean that neither option can be completed within a period of several decades. This unavoidably long timescale allows time for the


choices between ‘Use’ and ‘Disposal’ to be properly examined which the authors argue is essential given that any choice will almost certainly exclude any subsequent move to another choice. 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, the pros and cons of which are examined at length in this paper and its appendices. This evaluation is a responsibility of Government. “Decide in haste, repent at leisure” has been a long-time feature of UK decision making in nuclear power. It is inevitable that the varied drivers will complicate the choice of the way forward – security, the drive to Net Zero, and the view of the Treasury are examples. The interactions of these national policies make this a government-level decision.


Direct to disposal? The facilities, packaging and conditions of plutonium storage are currently the subject of an improvement programme by the UK’s Nuclear Decommissioning Authority


(NDA) that is expected to last several decades. The key initial finding of the report is that the current programme of improvement at Sellafield is essential to reduce the risks and hazards of plutonium storage, and this must be a priority for resources and funding over the next several decades. Furthermore, after storage period comes to an end, the


authors state, 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 UK’s planned Geological Disposal Facility (GDF). The storage of plutonium dioxide powder is more hazardous than storing the same plutonium as a reactor fuel or as a wasteform and this will need to be clearly factored into decision making, the report says. A complication with quantifying plutonium is that it


varies in its nuclide composition depending on the parent fuel’s burnup and irradiation conditions, the authors note, as well as physical properties such as particle size and purity. These variations can affect the future treatment routes of the material. In addition, the report says, the condition of some of the PuO2


and its storage containers


has deteriorated with time, leading to the need to both repackage the material and examine the potential need for treatment or disposal of the handled material. The authors note that it has also been acknowledged that, as the material must be stored for at least another few decades, more durable arrangements are essential, and Sellafield has embarked on a programme of repackaging and committing the material to a more robust storage regime with a hundred-year design life. As the report continues, the optimal solid forms


for disposal and for use as future fuel are distinct, so converting the stored material for delivery of one option will foreclose alternatives. The authors add that it is therefore advisable to reach a decision on the ultimate endpoint before taking firm steps in any direction. As waste, no energy would be generated, however, this option might also be expected to reach an earlier end point than use as fuel and to involve less initial cost as part of the overall GDF programme.


Recommendations for next steps The concepts, arguments, and data in mapping plutonium choices are unavoidably complex and the objective of the report is to provide clarity for each choice – as the report notes, encompassing the good, the bad, and the ugly. The


report outlines 10 recommendations: ● Recommendation one: Before attempting to make and implement policy decisions regarding plutonium, the government should ensure that a national dialogue takes place allowing stakeholders from all sides to


Origin of the UK’s plutonium stock Origin


Magnox AGR


Foreign plutonium transferred to the UK Foreign owned Total


Tonnes of material 85.8


23.6 8.3


24.1 141.8 www.neimagazine.com | October 2023 | 21


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