US-based TerraPower has begun Step 1 of the UK’s Generic Design Assessment (GDA) process for its Natrium reactor design and has also established TerraPower UK Ltd, marking its first-ever international corporate expansion.
The UK Office for Nuclear Regulation, along with the Environment Agency and Natural Resources Wales, confirmed the start of the three step GDA. The Department for Energy Security and Net Zero (DESNZ) made the request to the regulators following its readiness review of the TerraPower entry application. This review concluded that the design is ready to enter the GDA process and the regulators have now finalised arrangements with TerraPower, enabling the GDA to begin.
The Natrium plant features a 345 MWe sodium-cooled fast reactor integrated with a molten salt-based energy storage system. The storage technology allows the facility to temporarily boost its power output to 500 MWe for over five hours, enabling it to follow daily electricity load changes and integrate with renewable energy sources. Construction is expected to involve approximately 1,600 workers, with 250 full-time staff required for operations.
GDA is a voluntary process that enables the regulators to assess the safety, security, safeguards and environmental implications of new nuclear power station designs before site-specific decisions are made. The company submitted its GDA application in October 2025 and received formal acceptance by DESNZ in February. TerraPower’s GDA application builds heavily on design data and safety evaluations vetted during its regulatory progression in the US.
In April, TerraPower has announced the start of construction of its Natrium plant, Kemmerer unit 1 in Wyoming after the US Nuclear Regulatory Commission (NRC) granted the first-ever construction permit for a commercial-scale advanced NPP in March. Completion is targeted for 2030. The total project cost is estimated at $4bn, with the Department of Energy (DOE) providing half through its Advanced Reactor Demonstration Program (ARDP).
“TerraPower is entering the UK market with a long-term commitment to supporting the nation’s clean energy future and establishing ourselves as a serious and reliable deployment partner,” said Chris Levesque, President and CEO of TerraPower. “Starting Step 1 of the GDA process and establishing TerraPower UK mark major advances in our mission to bring the Natrium technology to Britain.”
Diego Fernandez Lisbona, ONR’s Head of Regulation for the TerraPower Natrium GDA and Advanced Nuclear Technologies, noted: “Interactions in 2025, through our framework for Early Engagement, have provided early design familiarity and we will continue to engage closely with TerraPower and broader stakeholders as GDA progresses.”
Alan McGoff, the Environment Agency’s Policy Lead New Nuclear Build, said: “GDA’s purpose is to de-risk future Natrium projects by ensuring that environmental protection is built into the design from the start. This is the first GDA where we can take advantage of our arrangements for enhanced cooperation between international regulators following the UK and US governments’ signing last year of the Atlantic Partnership for Advanced Nuclear Energy.”
Yeliz Marshall, Radioactivity and Industry Policy Senior Specialist Advisor at Natural Resources Wales said the GDA provides a valuable route to embed environmental protection early in the Natrium design and address key risks ahead of any future deployment. “This GDA also creates scope to benefit from closer international regulatory working under the UK-US Atlantic Partnership for Advanced Nuclear Energy.”
Announcing the launch of TerraPower UK Ltd, TerraPower said Dr Ian Hudson had been appointed to lead the new company “at a pivotal moment when the advanced nuclear industry is accelerating in Britain”. Dr Hudson brings more than 30 years of experience spanning technical project delivery, decommissioning, and corporate nuclear strategy.
He holds a PhD and a B.Sc. in Chemistry from the University of Liverpool. His UK nuclear background includes roles as Senior Director and Head of Nuclear at KBR, Group Vice President at AECOM, and Programme Director for the Nuclear Decommissioning Authority (NDA). At TerraPower UK, he is responsible for driving the Natrium technology from early development through to commercial delivery. This includes acting as the primary liaison with British regulators and industry partners.
TerraPower UK serves as the company’s first-ever international office, establishing a permanent operational base to navigate British regulatory frameworks and develop localised commercial pipelines.
The new subsidiary operates with three distinct tactical mandates designed to embed the US firm into the UK energy landscape. The office serves as the central hub for the GDA. It leverages the “Atlantic Partnership for Advanced Nuclear Energy” – a US-UK agreement enabling fast-tracked, enhanced cooperation between international regulators.
UK subsidiary will build local industrial partnerships to construct future Natrium facilities. Global consultancy Mott MacDonald has already been selected as the delivery partner to manage and deliver core GDA documentation. While TerraPower’s immediate priority is finishing its 345 MWe demonstration plant in Kemmerer, Wyoming by 2030, the UK office is developing the commercial pipeline to replicate this model across UK sites
“I’m thrilled to be joining TerraPower at such an important moment as we begin Step 1 of the GDA process in the UK,” said Dr Hudson. “Establishing a permanent presence enables us to work closely with our partners to deliver the critical energy infrastructure needed to support the UK’s clean energy transition and economic prosperity.”
