TerraPower Breaks Ground | America's First Advanced Nuclear Reactor Era Begins in Wyoming

A new chapter for American energy officially began on Wednesday, April 22, 2026, as TerraPower — the nuclear innovation firm founded by Bill Gates — broke ground on the nuclear island components of its flagship Natrium power plant in Kemmerer, Wyoming. The event marks the first time in over 40 years that a commercial non-light-water reactor has been permitted and begun physical nuclear construction in the United States, signaling a decisive shift toward Generation IV nuclear technology.

The Natrium Reactor Technology | Why Sodium Cooling Changes Everything About Nuclear Safety

Unlike every commercial nuclear plant currently operating in the United States, which uses pressurized or boiling water to cool the reactor core, the Natrium plant uses liquid sodium metal as its coolant. This single design choice cascades into a set of engineering advantages that proponents argue make it categorically different from the nuclear plants the public associates with Chernobyl and Three Mile Island.

• Steady-state output: The plant generates 345 megawatts (MW) of continuous baseload power — enough to supply approximately 250,000 homes.
• The "Energy Island" storage system: The Natrium's integrated molten salt thermal storage system acts as a giant heat battery. When grid demand spikes, the plant can draw on stored heat to boost output to 500 MW for up to five and a half hours — a flexibility that no existing nuclear plant can match.
• Lower pressure, higher safety: Sodium coolant operates near atmospheric pressure, eliminating the catastrophic depressurization risk that characterizes light-water reactor failures. The Natrium is designed to achieve a safe shutdown passively, without operator intervention or external power.

Kemmerer, Wyoming | From Coal Town to Nuclear Pioneer

The site selection for America's first advanced nuclear reactor was not accidental. Kemmerer was chosen from four Wyoming candidate cities because it sits next to the retiring Naughton Power Plant, a coal-fired facility operated by PacifiCorp — a subsidiary of Warren Buffett's Berkshire Hathaway Energy and TerraPower's grid partner on the project.

Reusing the Naughton site gives the project three structural advantages: existing high-voltage transmission infrastructure already connected to the Western grid, a trained local workforce familiar with large-scale power plant operations, and the political and community goodwill of a town that needs economic reinvention after coal's decline. TerraPower has committed to transitioning Kemmerer's coal workers into nuclear operations roles.

Breaking the U.S. Nuclear Regulatory Deadlock | The NRC Permit That Took Four Decades to Happen

The construction start follows what nuclear energy advocates have described as a historic regulatory efficiency milestone. The Nuclear Regulatory Commission (NRC) issued the construction permit for Kemmerer Unit 1 on March 4, 2026 — the first construction permit for a non-light-water reactor in U.S. history, completing its full safety review in approximately 18 months, nearly a year ahead of schedule.

The NRC's accelerated timeline is widely attributed to its new Part 53 licensing framework, a modernized regulatory pathway specifically designed for advanced reactor technologies that do not fit the assumptions built into light-water reactor regulations from the 1970s. In October 2025, the project completed its final Environmental Impact Statement, with no significant adverse findings.

The $4 Billion Public-Private Partnership | DOE, Bill Gates, and Warren Buffett's Wyoming Bet

The Kemmerer project is structured as one of the most high-profile clean energy public-private partnerships in U.S. history, combining federal funding, billionaire capital, and utility infrastructure into a single $4 billion construction program:

Why Natrium Solves the Grid's Biggest Problem | Dispatchable Clean Power at Scale

The U.S. electricity grid is undergoing its fastest transformation in a century. Wind and solar capacity are expanding at record pace, but both are intermittent by nature — they produce power when weather permits, not when consumers demand it. The grid increasingly needs what energy engineers call "dispatchable" clean power: zero-carbon generation that can be called upon at any hour, in any weather.

Traditional nuclear plants provide this baseload function but cannot flex their output. The Natrium's molten salt storage system changes that equation. When wind and solar are generating abundantly, the Natrium stores excess heat. When the sun goes down or the wind drops, it releases that stored heat to push output to 500 MW — filling exactly the gap that makes renewable-heavy grids vulnerable to price spikes and reliability failures.

This positions Natrium not as a competitor to renewables but as their complement — a firm, dispatchable backstop that makes an otherwise intermittent grid reliable at scale.

What Comes Next | From Wyoming Blueprint to National Nuclear Fleet

TerraPower is explicit that Kemmerer is not an endpoint. It is a proof-of-concept designed to serve as a commercial blueprint for a future fleet of Natrium plants across retiring coal communities in the American West, Midwest, and beyond. If the plant delivers on its 2030 target on time and within budget, the economic and regulatory case for accelerated deployment of additional units becomes dramatically stronger.

Internationally, TerraPower notified the British Office for Nuclear Regulation in March 2026 that it intends to enter the Generic Design Assessment process for the Natrium in the UK — the first formal step toward deploying the design outside the United States.

For decades, advanced nuclear power existed as a laboratory ambition, perpetually a decade away from commercialization. With a TerraPower crew breaking ground in Wyoming in April 2026, it is now a physical reality — and the most consequential test of whether Generation IV nuclear can deliver on the promise its proponents have made for forty years.