UK-first nuclear milestone reached at Sellafield

The Nuclear Decommissioning Authority (NDA) has achieved a UK-first nuclear safety milestone by successfully processing a can of plutonium residue into a stable waste form for the first time.
The breakthrough represents a major step towards the permanent disposal of the UK’s plutonium legacy and marks the launch of a new programme at the NDA group’s Sellafield site.
Around 400 cans of plutonium residue, produced as a by-product of historic fuel and materials manufacturing processes, will now be processed as part of the programme. The material is being treated in an existing Sellafield plant that has operated safely since the mid-1980s, before being prepared for eventual disposal in a Geological Disposal Facility (GDF).
The NDA said adapting and repurposing existing facilities, rather than building new infrastructure, has allowed the work to progress more quickly while offering better value for taxpayers.
David Peattie, group chief executive of the NDA, described the achievement as a significant demonstration of the organisation’s expertise.
“This UK-first milestone demonstrates the unrivalled expertise of the NDA Group, with special recognition for the Sellafield team whose innovation and specialist skills have made this achievement possible,” he said.
“The full immobilisation programme will take many decades, but processing this first can of residue into a disposable form represents real progress and was achieved within 12 months of the policy being announced.
“Tackling the UK’s plutonium challenge will remain a top priority for decades, and with the support of significant government investment, we are proud to be leading work that will make the UK safer for generations to come.”
Lord Vallance, minister for science, innovation, research and nuclear, said the milestone highlighted the UK’s leadership in nuclear legacy management.
“This achievement is a testament to the UK’s leadership in innovation and nuclear legacy management, made possible by the expertise and commitment of the workforce at Sellafield,” he said.
Sellafield chief executive Euan Hutton said managing the UK’s plutonium stockpile would dominate work at the site for decades.
“Turning the world’s largest stockpile of this extremely hazardous substance into a safe form and disposing of it will shape our work for many years,” he said.
“This milestone allows us to deal with some of the more problematic plutonium now, putting material beyond reach sooner and reinforcing our commitment to addressing the legacy of decades of reprocessing activity.
“Our specialist workforce, trained in unique ‘alpha’ skills, has adapted processes to handle material never managed before. Their innovation and dedication deserve recognition.”
Following this initial success, the NDA group will now move on to the far larger challenge of immobilising the UK’s entire civil separated plutonium inventory. The government formally tasked the NDA with this work in January 2025.
Plutonium immobilisation is designed to permanently place the material beyond reach, reducing long-term safety and security risks. Most of the UK’s plutonium exists in a highly hazardous oxide powder form, which cannot be treated using existing processes.
As a result, the programme will require the development and testing of first-of-its-kind technology to lock the material into a stable form suitable for permanent disposal in a GDF. This will also require the construction of a new processing plant and interim storage facilities at Sellafield.
The government has allocated £154 million over five years to support the NDA group in delivering this work. Early progress has already been made through the plutonium residue programme.
The funding will also support the design, installation and operation of specialist laboratory facilities at Sellafield, allowing experts to test and validate new immobilisation technologies. The investment is expected to support around 100 jobs, most of them based in Cumbria.
The NDA group, including Sellafield Ltd and Nuclear Waste Services, will work in partnership with the UK National Nuclear Laboratory and the wider supply chain to deliver the programme.