NRC Grants TerraPower Permit for Kemmerer Natrium Reactor, First in Nearly Decade

The Nuclear Regulatory Commission voted March 4, 2026 to grant a construction permit to US SFR Owner, a TerraPower subsidiary, for Kemmerer Power Station Unit 1 in Kemmerer, Wyoming, a decision outlets describe as the first commercial-scale advanced reactor construction permit in nearly a decade. TerraPower said it plans to start construction on the Natrium plant in the coming weeks; company CEO Chris Levesque called the vote “a historic day for the United States’ nuclear industry.”

Natrium is a sodium-cooled fast reactor with a base electrical output of 345 megawatts electric and an integrated molten salt thermal energy storage system that can boost output to 500 MWe for more than 5½ hours. The design separates the reactor facility and the energy-generation facility into two islands, a configuration TerraPower and analysts say is intended to reduce regulatory burden and speed construction.

TerraPower submitted a Part 50 construction permit application in March 2024 and the NRC docketed the application in May 2024. The NRC originally set a 27-month review schedule, but multiple outlets report the NRC completed its technical review in 18 months. Finance Yahoo attributed the accelerated review to TerraPower’s complete and responsive application, concentrated NRC staff effort, Congressional support through the Nuclear Energy Innovation and Modernization Act, and referenced Presidential executive actions supporting nuclear energy.

TerraPower framed its regulatory work as years in the making. Company materials state the team “has worked relentlessly for over 4 years with the NRC staff” and that the firm submitted its construction permit application “almost 2 years ago,” adding that it has invested “thousands of manpower hours” in the process. Levesque’s statement reproduced by multiple outlets adds, “We plan to start construction on the Natrium plant in the coming weeks and look forward to bringing the first Natrium reactor and energy storage system to market in the great state of Wyoming.”

The Natrium concept was introduced in August 2020 by TerraPower and GE Hitachi Nuclear Energy. The Department of Energy selected Natrium for the Advanced Reactor Demonstration Program in October 2020 and planned a combined $3.2 billion investment in the Natrium and X-energy Xe-100 projects. TerraPower announced a partnership with utility PacifiCorp in June 2021 and officially selected Kemmerer as the preferred site in November 2021; the Kemmerer site sits near the Naughton coal-fired plant, a 448-MWe unit slated for conversion to natural gas by 2026.

The project has attracted notable industry and investor activity. GeekWire reported a deal with Meta to build up to eight advanced reactors in the U.S., with the first two potentially online as soon as 2032 and all eight by 2035 if fully executed. GeekWire also noted prior investments including SK’s $250 million and a reported KHNP involvement, plus a manufacturing collaboration with HD Hyundai and memorandums of understanding with Utah and Kansas government departments.

Reports differ on immediate construction status: GeekWire states that construction activity in Kemmerer began in 2024, while TerraPower’s public materials say major construction will begin in the coming weeks following the NRC vote. The supplied materials do not specify what 2024 work entailed, leaving open whether that activity was site preparation or other non-nuclear enabling work.

TerraPower lists media contact press@terrapower.com and describes itself as a Bellevue, Washington-based company founded by Bill Gates and partners. With the NRC permit issued, the company and partners will move toward the next milestones; outlets report operational targets ranging from the end of 2030 to the early 2030s for commercial operation of Kemmerer Unit 1.