The first grid-scale advanced nuclear reactor is a step closer to reality in the U.S. X-energy has cleared a significant regulatory hurdle, inching the company toward construction.

The U.S. Nuclear Regulatory Commission (NRC) completed its safety review for the company’s Xe-100 reactor design. Partnering with Dow under the U.S. Department of Energy’s Advanced Reactor Demonstration Program, X-energy plans to build the project at the proposed Long Mott Generating Station. The Advisory Committee on Reactor Safeguards, an independent group advising the commission, also supported the staff’s findings to support issuing a construction permit.

A Smaller Footprint for Big Industry

Xe-100 advanced reactor
Xe-100 advanced reactor; Photo: X-energy

Traditional light-water reactors require a 10-mile emergency planning zone. But the Xe-100 is different. It uses passive physics, a pebble-bed core, and special TRISO-X coated particle fuel. These features minimize the needed emergency planning zone down to just 400 meters.

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That smaller footprint means companies can place reactors in areas where clean heat and electricity are needed most, even inside an industrial facility’s gates or closer to populated towns.

“Licensing a new reactor is earned through the quality of the application and the rigor of the regulator’s review,” said Dragan Popovic, Chief Global Operating Officer at X-energy. “The NRC’s completion of its safety review reflects years of disciplined work by our team and the NRC staff, establishing the foundations to support every Xe-100 application that follows on the path to scale.”

Built on Decades of Research

The design builds on over 20 years of testing and research by the U.S. Department of Energy. It also marks the first time a high-temperature gas-cooled reactor used the NRC’s updated risk-informed licensing framework, which sets a clear path for future builds.

The project already cleared its environmental review in May 2026, when the NRC issued a Finding of No Significant Impact. With safety and environmental checks finished, the project is heading into the final stretch for its official construction permit. Across the Atlantic, the Xe-100 also entered the Generic Design Assessment in the United Kingdom, opening another door for international growth.