Federal regulators have given Bill Gates-founded TerraPower the green light to build a first-of-its-kind advanced nuclear reactor in the small coal town of Kemmerer, Wyoming, a decision that could accelerate the nation’s pivot toward next-generation atomic energy.
The Nuclear Regulatory Commission issued construction permit CPAR-1 to US SFR Owner, LLC, a TerraPower subsidiary, authorizing construction of Kemmerer Power Station, Unit 1 in Lincoln County. Authorized under Commission Order CLI-26-5, the permit clears the company to begin major site work and pour safety-related concrete for a sodium-cooled Natrium reactor rated at 345 megawatts, with the ability to surge to 500 megawatts during periods of peak grid demand.
It is the first commercial nuclear construction permit the NRC has granted in decades and the first ever issued for a non-light-water reactor design under the agency’s modern licensing framework.
Why the Natrium design is different
Every commercial reactor currently operating in the United States uses water as both coolant and neutron moderator. The Natrium plant breaks from that model by using liquid sodium as its primary coolant, paired with a molten salt thermal energy storage system. That pairing lets operators ramp electricity output up or down depending on what the grid needs, a trait that could make the plant far more useful alongside variable wind and solar generation than a conventional nuclear station locked at a fixed output.
The reactor will also require high-assay low-enriched uranium, or HALEU, a specialized fuel that only a handful of facilities worldwide can produce. Centrus Energy began limited HALEU production at its Piketon, Ohio, facility in late 2023, but domestic supply remains constrained, and scaling it up is one of the project’s critical dependencies.
A coal town’s second act
Kemmerer, population roughly 2,600, has been shaped by coal mining and coal-fired power for more than a century. The Natrium plant is sited near PacifiCorp’s retiring Naughton coal station, and the project is designed to reuse existing grid connections and, potentially, parts of the local workforce.
For residents, the promise is tangible: construction jobs in the near term and permanent operations positions once the plant is running. But the NRC’s permit documents focus on safety and environmental compliance, not on workforce guarantees. Training pipelines, apprenticeship programs, and local hiring commitments will be shaped by separate agreements at the state and company level, details that have not yet been made public.
How the review unfolded
The NRC accepted TerraPower’s construction application in early 2024, triggering parallel safety and environmental reviews. Staff examined core design, sodium coolant behavior, seismic performance, emergency planning, and quality assurance, completing the final safety evaluation in roughly 18 months, ahead of the agency’s own projected schedule. Reviewers concluded there were no safety aspects that would prevent issuing the permit.
On the environmental side, the NRC published its final Environmental Impact Statement for the Kemmerer site in October 2025. Cataloged as NUREG-2268, the EIS assessed land use, water resources, ecological impacts, radiological consequences, and alternatives to the proposed action. Each stage of the review generated public documents and opportunities for community and stakeholder input before the Commission voted to issue the permit.
The Department of Energy’s Advanced Reactor Demonstration Program has backed the Natrium project with roughly $2 billion in cost-sharing funds, helping de-risk early-stage engineering and design work. While DOE’s role is separate from the NRC’s safety mandate, the combined federal support signals that Kemmerer is a flagship effort in Washington’s broader push for advanced nuclear technology.
What remains uncertain
The permit authorizes construction but not operation. Before TerraPower can load fuel and generate electricity, the company must secure a separate operating license, a process that involves additional safety analyses, inspections, and verification that the as-built plant matches the licensed design. TerraPower has publicly targeted commercial operation around 2030, though no binding schedule has been set.
Cost is another open question. The total project price tag has been widely estimated at roughly $4 billion, but TerraPower has not disclosed detailed construction cost breakdowns or the electricity price the plant would need to charge to recover its investment. Neither NRC nor DOE documentation tied to the permit specifies capital expenditure figures.
Supply chain readiness adds further uncertainty. Sodium-cooled reactors require specialized components: liquid sodium coolant, heat exchangers rated for liquid metal service, and HALEU fuel assemblies. The United States has limited domestic capacity for several of these items, and the public regulatory filings do not confirm whether TerraPower has locked in suppliers for every critical-path component. Any bottleneck in fuel fabrication, sodium procurement, or large-component manufacturing could push timelines beyond current expectations.
What Kemmerer means for the next wave of reactors
The 18-month safety review is drawing attention from other advanced reactor developers, including Kairos Power and X-energy, who are watching to see whether the NRC can sustain a similar pace for different designs and more complex sites. For now, the Kemmerer case is best understood as an important data point rather than a guaranteed template. The review benefited from strong federal backing, a relatively straightforward site, and years of pre-application engagement between TerraPower and NRC staff.
Still, the permit removes one of the longest-lead regulatory risks from the project and sends a concrete signal to investors, utilities, and policymakers: advanced non-light-water reactors can clear the federal licensing hurdle faster than many in the industry expected. Whether TerraPower can now deliver the plant on time and on budget will determine how much that signal is worth.
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*This article was researched with the help of AI, with human editors creating the final content.
