The Higher Activity Waste (HAW) programme at Trawsfynydd power station has been successfully completed following two decades of innovation, teamwork, and commitment. Built in the early 1960s, Trawsfynydd produced electricity for nearly 30 years and stands as the UK's only inland nuclear power station. Since it stopped generating power, operations have focused on safely managing its legacy, reducing risk, and preparing the site for long-term decommissioning.

The HAW programme specifically targeted intermediate-level waste, a mid-range category of radioactive waste that is more active than everyday low-level waste but less hazardous than high-level waste. The project involved retrieving legacy material, processing it safely, and placing it into secure, long-term storage on site. Nearly 2,300 individual waste packages were completed in total, representing a major delivery milestone and the removal of the site's primary hazards.

Rob Fletcher, CEO at Nuclear Restoration Services (NRS), said the completion of the programme marks a turning point for the site - "This is not just the end of a major programme, it is the end of an era."

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The safe and successful completion of this work allows Trawsfynydd to transition into its next delivery phase, which involves reducing the height of the reactors by nearly half. This project will bring about the most noticeable change to the local landscape in decades.

Tom Williams, NRS Trawsfynydd Site Director added: "Bringing the HAW programme to a close is a remarkable achievement for everyone at Trawsfynydd. Its completion represents a key delivery milestone in our decommissioning mission; one we can look back on with pride whilst also looking forward with excitement to the start of our new major projects."

The long-running campaign concluded with the transfer of the final waste package into storage. Throughout the process, teams designed practical and innovative working methods to safely retrieve the waste, including utilizing specialist vacuum equipment to collect fine dust and small fragments, alongside a robotic arm to remove material from deep storage areas. The insights gained from this work were shared with other sites nationwide to improve efficiency, lower costs, and support delivery across the wider decommissioning programme.

Clive Nixon, the NDA’s Chief Nuclear Strategy Officer, said: "This milestone demonstrates the significant progress we are making in delivering on our mission, set on behalf of government, to safely, securely and cost effectively clean up the UK’s earliest nuclear sites, prioritising the reduction of the highest hazards and risks while protecting people, communities and the environment.

"We look forward to the next phase of work, which will see the height of the reactors reduced, taking a big step towards their dismantling, as we progressively deliver on our mission to decommission the site."

It was announced in October 2025 that Costain had been appointed as the principal contractor to lower the height of the reactor buildings from approximately 54m down to 29m. The project is valued at up to £70 million and is expected to take up to four years to complete. At its peak, Costain is anticipated to employ more than 100 people to deliver the programme, creating opportunities to enhance regional skills development and make a lasting contribution to the local economy.