TerraPower gets permit to build first Natrium plant
TerraPower has cleared an important regulatory hurdle for its first commercial Natrium deployment in Wyoming, after the US Nuclear Regulatory Commission authorised staff to issue a construction permit for Kemmerer Power Station Unit 1. The decision matters well beyond one site: it is the first commercial reactor construction approval in the US in nearly a decade, and the first for a non-light-water reactor in more than 40 years.
TerraPower Natrium reactor clears a key step
The project is being developed by US SFR Owner, a TerraPower subsidiary, in Lincoln County, Wyoming, near an existing coal-fired power plant. The Natrium design is a sodium-cooled fast reactor with integrated molten-salt energy storage. According to the NRC, the plant is rated at 345 MW electric, with the storage system able to lift output temporarily to 500 MW when needed.
That makes this a notable step for advanced nuclear, but not the finish line. The construction permit allows TerraPower to start building; it does not authorise operation. A separate operating licence will still be required before the plant can begin generating power commercially. That distinction is worth keeping in view, because first-of-a-kind nuclear projects have a habit of looking simpler on announcement day than they do once concrete, steel, fuel and schedules get involved.
What the TerraPower Natrium reactor means
For TerraPower, the approval validates years of work on a design it has promoted as more flexible than a conventional large reactor. The company says the integrated storage system can help the plant respond to changes in grid demand, which is one reason advanced nuclear developers are drawing renewed attention as utilities and hyperscalers look for firm low-carbon power. As eeNews Europe recently reported in its coverage of big-tech nuclear power procurement, data-centre electricity demand is increasingly shaping how new generating capacity is being planned.
The NRC said TerraPower filed its construction permit application in March 2024, with formal review beginning in May 2024. The regulator completed its technical review in less than 18 months, issued its safety evaluation in December 2025, and completed the site’s final environmental impact statement in October 2025. TerraPower, in its own statement, described the permit as a milestone for the Natrium programme and for US advanced-reactor deployment more broadly.
The bigger question now is whether the TerraPower Natrium reactor can stay on schedule and prove that advanced designs can move from attractive PowerPoint material to repeatable infrastructure. For now, the permit is real, the reactor is still unbuilt, and the hardest part is only just starting. More detail on the permit decision is available from the NRC’s announcement of the construction approval.
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