Major decommissioning contract awarded at Trawsfynydd site
Source: gov.uk (2025-10-06)

NRS has appointed Costain as the principal contractor to reduce the height of two reactor buildings at Trawsfynydd former nuclear site, in Gwynedd, North Wales.

Nuclear Restoration Services (NRS) has appointed Costain as the principal contractor to reduce the height of two reactor buildings at Trawsfynydd former nuclear site, located in Gwynedd, North Wales.

Valued up to £70 million, this transformative project represents a major milestone in the region’s regeneration. At its peak, Costain is expected to employ more than 100 people to deliver the programme, creating opportunities to boost regional skills development and make a lasting contribution to the local economy.

This is a pivotal moment for Trawsfynydd,” said Rob Fletcher, Chief Executive Officer for NRS.

After years of careful planning and preparation, we’re now moving into the delivery phase of one of the most complex and ambitious decommissioning projects in the UK. We’re delighted to be working with our supply chain partners to shape this next stage in the site’s journey, ensuring the work is undertaken safely, securely and sustainably for all our futures.

David Peattie, Nuclear Decommissioning Authority (NDA) group Chief Executive Officer said:

This is a tangible step forward in one of the most significant projects in the NDA group’s portfolio and really embodies our commitment to delivering on a safer, cleaner future for generations to come.

Reduction of the reactor buildings will not only advance our mission but also create first-of-its-kind opportunities for Wales, showcasing innovation and leadership in nuclear decommissioning.

Trawsfynydd site following reactor height reduction

The two reactor buildings, now over 60 years old, have experienced structural wear due to prolonged exposure to the elements.

Set to begin this autumn, the project will reshape the site’s iconic skyline through the partial removal of the upper sections of both reactor buildings, lowering them from approximately 54m to 25m. This will be the most dramatic visual transformation the region has seen in decades.

Extensive enabling work has already been completed, including the installation of new internal roofs at a lower level, major de-planting of the primary boiler sections, and rerouting of electrical supplies - all designed to prepare the buildings for safe and efficient demolition.

The programme is expected to take around four years and forms part of a broader vision to transform the site, unlocking future opportunities for growth, innovation, and sustainable development.

Rt Hon. Liz Saville Roberts MP, added:

I welcome the appointment of a contractor tasked with reducing the 55-metre reactor buildings at Trawsfynydd. As a lead and learn site for the NRS rolling programme for decommissioning, Trawsfynydd exemplifies safe, sustainable, and secure delivery.

This next phase marks a visible transformation for the region and reinforces the site’s ongoing contribution to the local economy. It’s vital that the programme continues to support local recruitment and businesses. I also welcome the anticipated workforce growth and ask all stakeholders to work together to ensure continuous progress at this unique site in the heart of a national park.

As the appointed principal contractor, Costain brings a proven track record in delivering complex, safety-critical infrastructure projects, making them ideally placed to lead this transformative work.

Sam White, managing director, natural resources at Costain, commented:

Whether it’s designing the infrastructure that will produce the next generation of advanced nuclear fuel, plant optimisation or managing large-scale decommissioning programmes, Costain has decades of experience delivering predictable, best-in class solutions across the entire nuclear energy lifecycle.

This work is all part of creating a sustainable future, and we’re looking forward to deepening our relationship with NRS and working collaboratively with our local supply chain to complete this complex decommissioning project to the highest safety and quality standards.

The Trawsfynydd reactor buildings, originally designed by renowned architect Sir Basil Spence, were a bold statement of mid-20th-century industrial design. Their striking silhouette has long been a landmark in the region. This new chapter honours that legacy while embracing a future defined by delivery, transformation, and innovation.

During this time, local communities and visitors should expect increased activity on-site, including the presence of specialist equipment and construction teams. Every effort will be made to minimise disruption while maintaining safety and transparency throughout the process.