The Nuclear Regulatory Commission voted March 4, 2026 to approve the construction permit for TerraPower's Natrium reactor in Kemmerer, Wyoming, marking the first commercial advanced reactor construction permit issued in the United States in more than 40 years and the first non-light-water reactor approval since the early 1980s.
The Natrium plant will produce 345 megawatts of electricity using a sodium-cooled fast reactor design. TerraPower applied for the permit in March 2024 through its subsidiary US SFR Owner LLC, and expects to complete construction by 2030.
Natrium's sodium-cooled design operates at atmospheric pressure, a departure from the high-pressure containment systems required by traditional light-water reactors. The plant also incorporates a molten salt energy storage system that allows output to flex with grid demand, a capability of direct interest to utilities managing intermittent renewable capacity.
The approval represents a test case for the NRC's updated licensing framework under the ADVANCE Act, which requires advanced reactor permit decisions within 24 months. The Natrium review ran approximately 24 months from application to approval. Kemmerer was selected partly to provide employment continuity after the local Naughton coal plant closed.