TerraPower has begun full construction of its Natrium Advanced Nuclear Power Plant in Kemmerer, Wyo., following the issuance of a construction permit from the U.S. Nuclear Regulatory Commission, positioning the 345 MW project as the first utility-scale advanced reactor built in the United States.
The April 23 milestone shifts the estimated $4 billion project from initial, non-nuclear work, which began with a groundbreaking in June 2024, to full plant construction, advancing a federally supported demonstration aimed at validating the reactor’s advanced technology on a commercial scale.
The NRC permit was issued ahead of the September 2026 timeline previously cited in the ENR reports, following the completion of the agency’s safety assessment and environmental review.
“We’re not just moving forward on a single nuclear plant in Wyoming; we’re building America’s next generation of energy infrastructure,” said TerraPower President and CEO Chris Levesque, describing the Kemmerer Unit 1 project as a commercial project to mobilize a fleet of Natrium plants across the country and around the world.
Wyoming Gov. Mark Gordon (R) welcomed the milestone as a sign of the state’s continued energy leadership. “Wyoming has fueled this country for a long time, and today we’re leading again, this time in next-generation nuclear technology,” Gordon said, citing the project’s promise of reliable power and good-paying jobs.
Plant design and technology
The Kemmerer Unit 1 plant is designed around a sodium-cooled fast reactor combined with a molten salt energy storage system, a joint technology of TerraPower and GE Vernova Hitachi Nuclear Energy.
The system provides constant base load generation at 345 MW and can increase output to 500 MW during peak demand, enough to power approximately 400,000 homes, allowing the plant to supplement intermittent renewable resources on the grid.
Looking for quick answers on construction and engineering topics?
Try Ask ENR, our new intelligent AI search tool.
Ask ENR →
The plant is being developed under the U.S. Department of Energy’s Advanced Reactor Demonstration Program, a public-private initiative supported by about $2 billion in federal funding matched by TerraPower.
“The Natrium reactor demonstrates that when government and private industry work together, we can build a bright future for our nuclear-powered country,” said Rian Bahran, DOE Assistant Under Secretary for Nuclear Energy.
RELATED
Trump implements Defense Production Act to address grid equipment bottlenecks and energy projects
Scope of construction and labor
Bechtel is acting as the project’s engineering, procurement and construction contractor, a role it has held since 2020.
“The start of construction on Kemmerer Unit 1 marks an important step forward for the project and for the next generation of American nuclear power,” said Dena Volovar, president of Bechtel’s nuclear, safety and environmental business.
“By combining TerraPower’s reactor innovation with Bechtel’s processes, expertise and execution model, we will deliver these nuclear projects consistently, safely and at scale,” he added.
Early work has included site preparation and construction of non-nuclear support facilities and infrastructure, with reactor construction proceeding under federal authorization.
NRC spokesman Scott Brunell previously told ENR that the project would be reviewed as a full commercial power plant, not a non-electric demonstration facility, because it will produce electricity when completed.
With construction underway, TerraPower is mobilizing a workforce of approximately 1,600 artisans at maximum, with approximately 250 permanent employees expected once the plant becomes operational. The project is located on the site of the decommissioning of PacifiCorp’s Naughton coal-fired power plant and will supply electricity to the grid through Rocky Mountain Power, the project’s utility partner.
RELATED
$4B Advanced Nuclear Power Plant Package for Former Wyo. Coal Site
Marketing push
TerraPower has advanced efforts to commercialize the Natrium design ahead of the planned completion of the Kemmerer plant at the end of the decade.
The company has an agreement with Meta for up to eight Natrium plants by 2035, and in March 2025 announced a strategic alliance with professional services firm KBR to establish a replicable procurement framework for deployment in North America, the United Kingdom and the European Union.
TerraPower was the first US developer to apply for a construction and operation permit for a commercial-scale advanced reactor, submitting its application to the NRC in March 2024.
The start of nuclear construction at Kemmerer represents a key test of whether advanced reactor designs can move beyond pilot-scale development toward repeatable commercial delivery, a threshold the U.S. nuclear industry has not crossed in decades, and points to a potential path to turning retired coal assets into steady, dispatchable power generation.
