TerraPower Natrium 345 MWe Reactor with Molten-Salt Storage Enters UK GDA

TerraPower’s Natrium design — a 345 MWe sodium-cooled fast reactor paired with a molten-salt-based energy storage system that the company says can boost output to 500 MWe — has been accepted to enter the United Kingdom’s Generic Design Assessment process. The acceptance follows TerraPower’s October 2025 submission and was announced in a TerraPower press release and regulator updates on February 19, 2026.

The Department for Energy Security and Net Zero completed a readiness review of TerraPower’s application and formally asked UK regulators to begin the GDA process. Regulators named in the request are the Office for Nuclear Regulation, the Environment Agency and Natural Resources Wales. The ONR’s online notice said, “The assessment will begin once the necessary arrangements around timescales and resources have been put in place,” reflecting that a formal GDA start date and schedule have not yet been published.

Chris Levesque, TerraPower president and CEO, framed the filing as a technical milestone in the company’s Feb 19, 2026 CEO statement distributed from Bellevue, WA via PR Newswire at 12:54 ET. Levesque said, “We are incredibly pleased to have our application accepted into the UK’s Generic Design Assessment (GDA) process. TerraPower prides itself on its technical rigor, and we will bring our industry‑leading team and robust regulatory experience to support this review. We look forward to working with the Department for Energy Security and Net Zero (DESNZ), Office for Nuclear Regulation (ONR), and Environment Agency (EA) in the coming months, and ultimately advancing our efforts to bring a Natrium reactor to the United Kingdom.”

TerraPower’s press materials describe the Natrium technology as a sodium-cooled fast reactor with molten-salt storage and explicitly claim the storage allows rapid output increases to 500 MWe when needed; the PR note also states TerraPower considers this the only advanced reactor design with that feature. A PR Newswire footnote identifies the Natrium Reactor as a TerraPower and GE Vernova Hitachi Nuclear Energy technology, linking the design to GE Vernova and Hitachi Nuclear Energy in the company’s disclosures.

This GDA filing is TerraPower’s first regulatory submission for Natrium outside the United States. The company continues parallel work on a US Natrium project developed as a public-private partnership with the U.S. Department of Energy; TerraPower began construction on the non-nuclear portions of that US site in June 2024. Earlier reporting from April 18, 2025 noted TerraPower sent a formal letter to DESNZ signaling intent to enter the UK GDA, and summarized US milestones including NRC pre-application meetings, submission and acceptance of a Construction Permit Application, more than a year of NRC review on topical reports with the NRC reporting it was ahead of schedule, and a construction permit from the state of Wyoming for a site near a retiring coal plant.

British market context from April 2025 reporting cited The Telegraph’s short list of Rolls-Royce, GE Hitachi, Holtec and Westinghouse for Great British Nuclear contracts, and noted TerraPower’s UK bid could add competitive pressure to Rolls-Royce’s ambitions. With regulators ONR, EA and NRW asked to begin assessment, next steps hinge on those agencies setting timescales and resource plans; there is no public GDA start date, no published GDA timetable, and no UK site selection or commercial terms disclosed in the Feb 19, 2026 materials. The immediate runway is now procedural: regulators must arrange resources and TerraPower has committed to support the review as the UK assessment phase moves from readiness into formal evaluation.