The US Nuclear Regulatory Commission has issued a construction permit to TerraPower for a sodium-cooled nuclear reactor in Kemmerer, Wyoming, marking the agency’s first construction approval in nearly a decade.
The permit does not guarantee the plant will receive approval to operate, but it clears the most immediate regulatory barrier for the project. TerraPower, backed financially by Bill Gates, submitted its construction application to the NRC in early 2024. The agency completed its review nearly 10 months ahead of schedule, a pace that may reflect the influence of the ADVANCE Act, passed in June 2024, which sought to streamline nuclear project approvals and encourage next-generation reactor designs.
A Reactor Built Differently
The plant centers on a design called Natrium, developed jointly with GE Hitachi. Its most distinct feature is liquid sodium cooling, which keeps the primary coolant in a liquid state without the high-pressure steam challenges associated with conventional water-cooled reactors. The tradeoff is that sodium reacts violently when exposed to air or water, introducing its own handling risks.
Natrium is also a fast-neutron reactor, a configuration that can consume certain radioactive isotopes that standard reactor designs would leave as long-term waste. At 345 megawatts, it runs considerably smaller than a typical nuclear plant, which generally sits around one gigawatt.
The design includes an integrated energy storage system. Heat extracted by the sodium goes into a salt-based storage material rather than directly boiling water. That stored heat can generate electricity on demand, allowing the plant to work around periods when renewable energy sources push prices lower. During peak discharge, the storage system can temporarily boost output to 500 megawatts.
Rare Technology With a Long Road Ahead
Sodium-cooled reactors remain uncommon. Only about 25 significant examples have been built globally, most not designed for power generation. The United States has not built one since the 1960s and has not operated one since the 1990s. The Natrium design, as a first-of-its-kind commercial project, carries inherent risk well beyond the construction phase.
TerraPower selected the Kemmerer site in 2021. The project operates as a public-private partnership under the Department of Energy’s Advanced Reactor Demonstration Program. Completion is currently projected for 2030.
That timeline puts the plant well outside the window that datacenters and technology companies need to meet their near-term power demand. It also raises a political variable: a 2030 operational target would push the final operating license approval into a future administration, regardless of the current regulatory momentum.
First-of-its-kind construction projects routinely experience delays, and the Natrium plant has no precedent in modern US nuclear history to draw from. The construction permit is a real milestone, but the distance between breaking ground in Wyoming and delivering power to the grid remains substantial.
Photo by Lee Lawson on Unsplash
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