Trawsfynydd decommissioning project enters next phase

Nation.Cymru Staff

The next phase of the decommissioning of the former Trawsfynydd nuclear power station is under way after Nuclear Restoration Services handed control of the reactor buildings area to contractor Costain.

The handover allows Costain to begin on-site work at the Gwynedd facility, which has been undergoing decommissioning since 1991.

The project will run for around four years and will involve partially demolishing and stabilising the two reactor buildings ahead of later stages of decommissioning. Their height will eventually be reduced from about 54 metres to 25 metres.

Early work is already under way, with a crane on site to support the installation of scaffolding, hoists and electrical infrastructure. Larger crawler cranes are expected later this year, followed by two tower cranes inside the reactor buildings in early 2027.

Costain was awarded the contract, reported to be worth about £70 million, in October 2025. Its in-house engineering team will lead the programme, including the civil engineering and remedial work needed to support the deconstruction.

More than 100 people are expected to be employed at the site at the height of the programme, with opportunities for apprenticeships, training and local suppliers.

Trawsfynydd was a Magnox-design power station commissioned in the 1960s. It is one of six former UK reactor sites currently being dismantled that are also being considered for possible future nuclear development.

Costain has previously delivered enabling work at Trawsfynydd, including the installation of new capping roofs on the reactor buildings. It is also working with NRS on a separate six-year decommissioning programme covering 11 locations across the UK.

The handover followed a review by NRS and Costain which confirmed that the plans and arrangements for the work were progressing as expected.

Tom Williams, NRS Trawsfynydd site director, said: “Reaching this milestone reflects years of planning, preparation and collaboration for our dedicated workforce and supply chain partners.

“As well as delivering an important step forward in decommissioning, the project will create opportunities for local people and businesses, helping ensure benefits are felt beyond the site boundary.”

‘Lead and learn’

NRS describes Trawsfynydd as one of its “lead and learn” sites. It says the experience gained from the work will help inform future decommissioning programmes elsewhere.

James Trott, Costain’s project director, said the handover marked “a significant milestone in what is a highly complex decommissioning project”.

He added: “We’ve undertaken significant design and engineering works to reach this phase of the project and, as we progress the enabling works, we’ll be continuing to collaborate with NRS and our local supply chain to deliver all subsequent phases to the highest safety and quality standards.”

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