In the high desert of southwestern Wyoming, the coal-fired Naughton Power Plant has been winding down for years. Now, on that same stretch of land outside Kemmerer, workers are preparing to build something the United States hasn’t attempted in over a decade: a brand-new commercial nuclear reactor.
In April 2026, the Nuclear Regulatory Commission issued construction permit CPAR-1 to US SFR Owner, LLC, a subsidiary of TerraPower, the advanced nuclear company founded by Bill Gates. The permit authorizes construction of the Kemmerer Power Station Unit 1, a sodium-cooled fast reactor in Lincoln County, Wyoming. It is the first NRC construction permit for a commercial power reactor in roughly a decade, and it signals that the federal regulatory system has moved from reviewing advanced reactor designs on paper to greenlighting actual construction.
What the NRC has approved
US SFR Owner filed its construction application on March 28, 2024, under Part 50 of the NRC’s licensing framework. After completing safety and environmental reviews, the agency granted the permit, giving TerraPower legal authority to begin pouring concrete and erecting structures at the Kemmerer site.
The reactor design uses liquid sodium as a coolant instead of water. That allows it to operate at higher temperatures and significantly lower pressures than conventional light-water reactors, which TerraPower says improves both efficiency and safety margins. Sodium-cooled fast reactors have been studied for decades, but Kemmerer would be among the first built at commercial scale in the United States.
TerraPower has estimated the total project cost at up to $4 billion, with construction expected to begin shortly after the permit’s issuance. A significant share of the funding comes through the Department of Energy’s Advanced Reactor Demonstration Program, which selected TerraPower’s Natrium design for cost-shared support in 2020. The federal backing reflects Washington’s broader push to develop next-generation nuclear technology as demand for carbon-free, always-on electricity surges, driven in part by the explosive growth of AI data centers and new incentives under the Inflation Reduction Act.
A second project in Tennessee
Kemmerer is not the only advanced reactor moving forward. In November 2024, the NRC issued construction permits for Hermes 2, a test reactor facility developed by Kairos Power in Oak Ridge, Tennessee (docket numbers 50-611 and 50-612). Hermes 2 uses a molten fluoride salt coolant and is classified as a non-power test reactor. Its purpose is to demonstrate the technology’s performance and safety characteristics rather than to generate electricity for the grid.
Together, the Kemmerer and Hermes 2 permits represent the most active stretch of new nuclear licensing in the United States since the combined licenses for Vogtle Units 3 and 4 were issued in 2012.
Why Kemmerer matters for coal country
The choice of site is deliberate. By building next to a retiring coal plant, TerraPower can tap into existing grid connections, transmission lines, and industrial infrastructure. The company has also pitched the project as a lifeline for Kemmerer, a town of roughly 2,600 people that has long depended on fossil fuel jobs. Local officials and workers have voiced support, seeing the reactor as a way to keep high-paying energy jobs in the region rather than watch them disappear.
Supporters of the approach argue that pairing advanced reactors with former coal sites offers a politically and economically viable path to decarbonization, one that doesn’t ask energy communities to simply absorb the loss. If the model works at Kemmerer, it could become a template for similar conversions across the Mountain West and Appalachia.
The hard questions ahead
A construction permit, however, is not a finished reactor. Several major uncertainties remain.
The $4 billion cost estimate comes from TerraPower’s own projections, not from an independently audited budget. That distinction matters. The last major U.S. nuclear construction project, the Vogtle expansion in Georgia, saw its original cost estimate roughly double and its timeline stretch years beyond schedule. Whether TerraPower can avoid a similar outcome is an open question.
The timeline for actual electricity generation is also unclear. Under the Part 50 framework, a construction permit does not grant permission to operate. TerraPower must still complete fuel fabrication, component installation, extensive testing, and a separate NRC operating license review before the reactor can connect to the grid. No firm date for commercial operation appears in the current regulatory record.
Fuel supply adds another challenge. Sodium-cooled fast reactors require specialized fuel forms that are not yet produced at large commercial scale domestically. Delays in standing up reliable fuel manufacturing could ripple through the entire project schedule, though detailed procurement plans have not been made public.
For Hermes 2, the path forward depends on whether the test data it generates can support future licensing of larger molten-salt power reactors, a step that has not yet been formally proposed or scheduled.
What the permits actually prove
What the regulatory record establishes with confidence is that the federal government has moved from studying advanced reactor concepts to issuing the legal authorizations needed to build them. The NRC’s permit filings, accession numbers, and formal issuance records are primary documents. They confirm that specific entities have been granted specific construction authority at specific sites. That shift is real and documented.
The cost and timeline claims occupy different ground. They reflect what TerraPower says it plans to spend and when it plans to start, not independently verified outcomes. Given the nuclear industry’s recent history, those projections should be treated as stated intentions rather than guaranteed results.
If the Kemmerer reactor operates as designed, it would add reliable, low-emission baseload power to the regional grid and offer a replicable model for turning coal towns into nuclear communities. If the project stumbles, it risks reinforcing skepticism about whether advanced nuclear can deliver on its promises in time to matter for the climate. The permits are a genuine milestone. The real test is whether concrete, steel, and sodium can follow on schedule and on budget.
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*This article was researched with the help of AI, with human editors creating the final content.
