TerraPower launches UK review for Natrium reactor and energy storage

TerraPower has moved Natrium out of the concept stage and into the UK’s formal approval lane, a commercialization step that carries real weight in a crowded advanced-reactor field. With TerraPower UK Ltd now open as the company’s first office outside the United States, Britain is no longer just a theoretical export market. It is part of the near-term deployment plan, and the regulator’s queue is now where Natrium will be tested.

The company submitted the Natrium reactor and energy storage system into the UK Generic Design Assessment on October 19, 2025. UK regulators accepted it on February 19, 2026, and the Office for Nuclear Regulation, the Environment Agency and Natural Resources Wales began GDA Step 1 on June 16, 2026. That matters because GDA is not a site application. It is the point where safety, security and environmental questions are checked before a company locks in a specific build location, which can trim expensive redesign risk later.

For Natrium, the review reaches beyond a standard reactor package. TerraPower describes the design as a 345 MWe sodium-cooled fast reactor paired with molten-salt-based energy storage, with the system able to boost output to 500 MWe when needed. The Office for Nuclear Regulation says the process is three steps long, and the Department for Energy Security and Net Zero asked the regulators to begin only after a readiness review concluded the design was ready. That puts the plant’s core and its storage system under the same regulatory lens, which is exactly where an integrated advanced design either proves itself or starts to slip.

The filing also gives TerraPower a way to build credibility with partners before any shovel hits a UK site. In December 2025, TerraPower and KBR announced studies to evaluate potential UK deployment sites, showing the company is already moving from licensing into early commercial planning. A successful GDA would give TerraPower a regulator-tested route into a major export market, while also reducing timetable risk for later siting work.

The timing fits a broader UK push for new nuclear. The government’s civil nuclear roadmap keeps alive an ambition of up to 24 GW of nuclear capacity by 2050, enough to cover up to a quarter of projected electricity demand. The UK and U.S. regulators have also refreshed their cooperation under the Atlantic Partnership for Advanced Nuclear Energy, with officials aiming to cut licensing timelines from roughly three or four years to roughly two. For TerraPower, Natrium’s UK review is the first hard test of whether that faster, transatlantic path can turn a headline design into a deployable export story.