TerraPower has begun construction of its flagship Natrium plant, Kemmerer Unit 1, which is on track to be the first utility-scale advanced nuclear power plant (NPP) in the US.

Natrium is a TerraPower and GE Vernova Hitachi Nuclear Energy technology.

This milestone follows the successful issuing of a construction permit by the US Nuclear Regulatory Commission and represents the "culmination of years of innovation, rigorous engineering and disciplined site preparation", said TerraPower.

"We are not just breaking new ground on a first-of-a-kind nuclear plant in Wyoming; we are building the next generation of America's energy infrastructure," said president and CEO Chris Levesque. "The Natrium plant will… serve as a commercial blueprint to mobilise a fleet of Natrium plants across the country and around the world."

The plant features a 345MW sodium-cooled fast reactor with an integrated molten salt-based energy storage system. The storage technology can increase energy output to 500MW at times of need. The energy storage capability is designed to keep base output steady, ensuring constant reliability, and can quickly ramp up when demand peaks. It is said to be the only advanced reactor design with this feature.

This first Natrium plant is being developed through the US Department of Energy's Advanced Reactor Demonstration Program, a public-private partnership. When complete, the project will be the first utility-scale advanced NPP in the US and Wyoming's first-ever commercial nuclear generating station. The project has been under active development on its greenfield site since June 2024 and has begun construction of non-nuclear support facilities.

TerraPower is engaged in rapid commercialisation of the Natrium technology, including an agreement with social media giant Meta for up to eight Natrium plants by 2035.