The technology
Terrapower’s Natrium 345 MWe sodium-cooled fast reactor has a molten-salt-based energy storage system which allows it to temporarily boost output to 500 MWe when needed, enabling the plant to follow daily electric load changes and integrate seamlessly with fluctuating renewable resources. The Natrium reactor is a TerraPower and GE Vernova Hitachi Nuclear Energy technology.
The licensing process
TerraPower submitted its construction permit application to the Nuclear Regulatory Commission (NRC) in March 2024 and it was docketed by the NRC and the formal review began in May 2024. The NRC established an initial 27-month review schedule, however the review was completed in 18 months after a streamlined mandatory hearing process.
TerraPower began non-nuclear construction for the Kemmerer, Wyoming, plant in June 2024, and expects the project – which is near a retiring coal plant – to be complete in 2030. It is being developed through the US Department of Energy’s Advanced Reactor Demonstration Program.
The NRC issued the construction permit last month, saying it was the first commercial reactor approved for construction for nearly a decade and the first non-light water reactor in more than 40 years.
What they said
Chris Levesque, president and CEO of TerraPower, said: “This is the moment our industry has been working toward for a generation. We’re not just breaking new ground on a first-of-a-kind nuclear plant in Wyoming; we’re building the next generation of America’s energy infrastructure. The Natrium plant will deliver reliable and dispatchable power to the grid and Kemmerer Unit 1 will serve as a commercial blueprint to mobilise a fleet of Natrium plants across the country and around the world.”
Wyoming Governor Mark Gordon said: “The start of construction on TerraPower’s Natrium plant in Kemmerer marks a major milestone not just for Wyoming, but for the future of American energy. Wyoming has long powered this country, and today we are leading again, this time in next-generation nuclear technology. This project reflects our commitment to reliable energy, good-paying jobs, and a future built on innovation and Wyoming values.”
US Senator John Barrasso said: “As the country’s number one producer of uranium, Wyoming is the perfect place to build TerraPower’s advanced nuclear reactor.”
Dena Volovar, president of Bechtel’s Nuclear, Security & Environmental business, said: “Bechtel is proud to partner with TerraPower as the engineering, procurement and construction contractor on the Natrium advanced reactor. By combining TerraPower’s reactor innovation with Bechtel’s processes, experience and execution model we will deliver these nuclear projects consistently, safely and at scale. By applying the latest digital tools and project delivery systems, Bechtel is uniquely positioned to deliver the nation’s first Natrium plant with efficiency and execution certainty.”
Background
Microsoft co-founder Bill Gates has been chairman of TerraPower since 2006. The firm’s molten salt-based energy storage system means the Natrium plant can temporarily boost output to 500 MWe when needed, enabling the plant to follow daily electric load changes and integrate seamlessly with fluctuating renewable resources.

How a Natrium plant might look, with the nuclear island on the right and the energy island on the left (Image: Natrium)
In January social media giant Meta announced that its future nuclear energy plans included funding to support the development in the USA of up to eight Natrium sodium fast reactors – two new units capable of generating up to 690 MW of firm power with delivery as early as 2032, plus the rights for energy from up to six other Natrium units capable of producing 2.1 GW and targeted for delivery by 2035.
In February the Narrium reactor was accepted into the UK’s Generic Design Assessment process.













