Trawsfynydd takes next step towards Reactor Height Reduction

NRS has handed over responsibility of the reactor buildings area to Costain, paving the way for the next phase of one of the major decommissioning projects.

The handover follows the award of a key contract to Costain in October 2025 to deliver reactor height reduction at Trawsfynydd.

One of the most significant programmes currently underway across the NRS estate, the project will reduce the height of both reactor buildings by nearly half. It will transform the site’s skyline, deliver the most visible change seen at Trawsfynydd in decades, and generate valuable learning that can be applied to future decommissioning projects across the UK.

The project will also bring wider benefits to the region, supporting employment, skills development, apprenticeships, and opportunities for local businesses and communities. At its peak, the programme is expected to create more than 100 jobs with Costain, helping to strengthen the local supply chain, boost regional skills, and make a lasting contribution to the economy.

Following the handover, NRS and Costain have also successfully completed a key review of the project, confirming that plans and delivery arrangements are progressing as expected. Completion of the review was an important step in allowing the programme to move forward towards future demolition works.

With the handover now complete, Costain has taken control of the reactor buildings area and can begin delivering the reactor height reduction project, representing the transition from years of planning and preparation into on-site delivery.

For the Trawsfynydd workforce that has supported the programme, the handover represents far more than the transfer of an area on site. It marks the successful completion of a major preparatory phase and demonstrates the progress made in bringing one of the UK’s most significant decommissioning projects closer to delivery.

A crane has already arrived on site to support a series of early activities, including scaffolding, hoist installation and electrical infrastructure works.

The most visible stage of the project is expected to begin later this year when large crawler cranes arrive on site. This will be followed in early 2027 by the erection of two large tower cranes within the reactor buildings, which will play a key role in the deconstruction process.

NRS Trawsfynydd Site Director, Tom Williams said:

“Reaching this milestone reflects years of planning, preparation and collaboration for our dedicated workforce and supply chain partners. I’d like to thank everyone whose hard work and commitment has helped us get to this point.

“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.

“Trawsfynydd has an important role as one of NRS’s lead and learn sites. The experience gained through this project will help inform future decommissioning programmes across the wider NRS estate and support the development of skills, knowledge and best practice.

Trawsfynydd takes next step towards Reactor Height Reduction - GOV.UK