The Nuclear Regulatory Commission approved a construction permit for TerraPower’s Kemmerer Unit 1 on March 4, 2026. The authorization allows development of the first commercial-scale Natrium sodium fast reactor in the United States, located near the Naughton power plant site in Wyoming. This decision marks the agency’s first approval for a non-light water commercial reactor in more than four decades and its first commercial reactor permit in nearly ten years.
What it means
The Natrium design, introduced by TerraPower and GE Hitachi Nuclear Energy in 2020, separates the reactor facility from the energy generation facility. The Kemmerer unit will have a rated output of 345 megawatts electric but can boost capacity to 500 megawatts electric for up to five and a half hours. TerraPower stated that construction is set to begin within weeks of the permit approval, with project completion targeted for 2030. This timeline extends three years beyond the original Department of Energy target established when the agency selected Natrium for the Advanced Reactor Demonstration Program in October 2020.
The licensing process utilized a fully risk-informed, performance-based approach, marking the first use of this methodology for a power reactor. TerraPower submitted its Part 50 construction permit application in March 2024, and the NRC formally accepted it in May 2024. Although the regulator shortened its review timeline in July 2025 to target an end-of-2025 decision, the final approval came three months later than that accelerated goal but five months ahead of the original August 2026 schedule. The Wyoming Industrial Siting Council had previously granted approval for non-NRC jurisdiction activities in January 2025. PacifiCorp remains a partner in the project, which is situated at a retiring coal plant site selected as the preferred location in November 2021.
Key facts
- NRC approved construction permit for Kemmerer Unit 1 on March 4, 2026.
- First NRC approval for a commercial non-light water reactor in over 40 years.
- First NRC approval for a commercial reactor in nearly a decade; Turkey Point-7 was the last in 2018.
- Natrium reactor rated at 345 MWe with capability to boost to 500 MWe for five-and-a-half hours.
- Project completion targeted for 2030, three years beyond original DOE target.
- TerraPower plans to start construction within weeks of permit approval.
- US SFR Owner, a TerraPower subsidiary, must submit a separate Part 50 operating license application.
- Licensing used the Licensing Modernization Project methodology endorsed by NRC in 2020.
Source: American Nuclear Society, reporting NRC announcement