X-energy, the Amazon-backed nuclear startup looking to revive the United States’ high-temperature gas-cooled reactor efforts, just took a major step toward securing federal permits to start construction on its debut plant.

On Monday, the Nuclear Regulatory Commission approved the key environmental review for X-energy​’s first project, which would see it build four of its 80-megawatt Xe-100 reactors at chemical giant Dow’s UCC Seadrift Operations, the 4,700-acre manufacturing complex on Texas’ Gulf Coast just north of Corpus Christi.

For months, the NRC conducted an environmental assessment of the proposed project — a step required by the National Environmental Protection Act for any large-scale energy project seeking federal permits. The results of that study determined whether a more rigorous, potentially yearslong environmental impact statement is needed. The agency, Canary Media has learned, has concluded the process with a ​“finding of no significant impact,” meaning that the project can forgo the impact statement.

This marks the first time in the NRC’s 52-year history that the agency has greenlit a commercial nuclear project’s environmental review through an assessment rather than an impact statement.

The environmental approval is the first of the two biggest steps in the construction permitting process, and is a requirement to complete the second stage: the safety review. X-energy expects the NRC’s staff to issue recommendations on the safety review in November, after which the five-member commission can render its final verdict at any time.

“We did the same studies you would for any reactor. We didn’t take any shortcuts. We didn’t try to game the system. And what we came out with was an assessment that told us that we had very minimal impacts,” said Robert Taylor, X-energy’s vice president of regulatory affairs and licensing.

“The ability within NEPA to do an environmental assessment and to reach a finding of no significant impacts has always existed,” he added. ​“But the conservative approach has always been to just start with an environmental impact statement, because the perception was the impacts will be big. That’s probably true for large light-water reactors, but it’s not necessarily true for small modular reactors like us.”

If approved, X-energy’s Xe-100 would signal a U.S. return to a commercial technology that effectively died out in 1989, near the end of America’s atomic heyday.

General Atomics built a 40-megawatt high-temperature gas-cooled reactor at the Peach Bottom Atomic Power Station along Pennsylvania’s Susquehanna River in 1966, but shut down the demonstration unit in 1974. The same developer started a larger, 330-megawatt project around the same time at Colorado’s Fort St. Vrain nuclear plant. That single high-temperature gas-cooled unit came online in 1979, but lasted only 10 years because of repeated technical malfunctions and steep repair costs.

X-energy’s permitting milestone comes amid a broader wave of activity in the long-stagnant U.S. nuclear sector. Two new commercial nuclear reactors broke ground last month, as many as three more decommissioned reactors are set to be restarted in the coming months and years, and several states that had banned nuclear construction in the mid-20th century are now lifting those moratoria.

It also comes nearly a year after the NRC agreed to speed up the permitting process for the firm’s first plant by setting an 18-month review schedule for the company. That’s roughly half the time the agency has historically taken to issue a construction permit.

The faster timeline reflects the NRC’s efforts to streamline reactor approval following orders by both the Biden and Trump administrations. Much of the regulatory overhaul currently underway at the NRC stems from the Accelerating Deployment of Versatile, Advanced Nuclear for Clean Energy (ADVANCE) Act of 2024, which former President Joe Biden signed after nearly unanimous approval in the U.S. Senate. The statute gave the NRC a clearer mandate to protect the public against not only the threat of nuclear accidents but also the risk that reactors don’t get built.

Then, in May 2025, President Donald Trump issued a series of executive orders designed to deepen the regulatory changes and spur new reactor construction — including the controversial move to replace the bedrock model for measuring the health risk of radiation exposure.

X-energy’s expedited pathway also highlights the benefits of the company’s early engagement with government programs and its efforts to court deep-pocketed corporate backers.

In 2015, the U.S. Department of Energy included X-energy in its Advanced Reactor Concepts program. When the DOE established the Advanced Reactor Demonstration Program in 2020, in which the federal government took on half the cost of building a participating company’s first reactor, X-energy was one of the first participants. While X-energy said it hasn’t released price projections for each project, the company disclosed to the Securities and Exchange Commission that the 50/50 cost-share agreement with the DOE covered a total estimated cost of up to $2.4 billion.

In 2022, X-energy announced Dow as its first commercial offtaker for the Texas project. Two years later, when the artificial intelligence boom spurred tech giants to sign a series of deals with nuclear startups, Amazon placed its bet on X-energy, vowing to help finance construction of 5 gigawatts of reactors through deals to buy power for its data centers. The company took an equity stake in X-energy, which went public on April 24 on the Nasdaq composite.

Amazon is now providing financing for the construction of X-energy’s second project, a multiphase expansion of an existing nuclear-energy complex in Washington state operated by the public utility Energy Northwest. Depending on the utility’s willingness to buy the units, the startup aims to eventually build up to a dozen of its Xe-100 reactors at the site.

On both projects, ​“a real differentiator for us is truly how we used our pre-application process with the NRC,” Taylor said. The company provided more than two dozen reports to the NRC ahead of submitting its application. ​“We submitted a vast number of topical reports and white papers that we got feedback on that informed the design and formed the regulatory submittals,” he said. ​“We substantially de-risked the project with the NRC through all of that engagement. Almost all the methodologies we use in designing the reactor and the support systems have been approved by the NRC.”

While rival developers of next-generation small modular reactors and microreactors have pushed for regulatory changes or new licensing pathways that are designed to benefit new technologies, X-energy chose the time-honored pathway for permitting its first two projects.

“Part 50 is a great process for new designs because it allows changes to the design as you construct,” Taylor said. ​“Once we get the first approvals of our design under Part 50, and we get through that first operating license, we’ll be in a position to take a standardized design back to the NRC.”

Among the design elements that Taylor said bolster X-energy’s safety qualities is the fact that the company is using tri-structural isotropic fuel, or TRISO for short. The fuel encases tiny bits of enriched uranium inside poppy seed–sized balls coated in ceramic materials that effectively make a meltdown impossible.

TRISO, however, is far more expensive than the traditional low-enriched uranium fuel used in light-water reactors, which has held back its adoption to date. Only one commercial reactor uses TRISO worldwide today: the high-temperature gas-cooled reactor that China hooked up to its grid in December 2022. Another experimental reactor operated by the Japan Atomic Energy Agency at a facility north of Tokyo, whose design a Japanese American startup is now looking to commercialize in the U.S., also uses TRISO, as do nearly half a dozen proposed designs now competing with X-energy.

Unlike many other next-generation reactor designs that are using coolants such as molten salt, liquid sodium, or lead, X-energy’s Xe-100 uses helium. This approach has decades of data to back it up, thanks to the earlier U.S. experiments with similar technology.

“Look, Peach Bottom and Fort St. Vrain were great opportunities to demonstrate the technology nearly 50-plus years ago. But in the ensuing 50 years, [high-temperature gas-cooled reactors] have been run in multiple countries throughout the world, and TRISO fuel has gone through extensive testing,” Taylor said. ​“HTGRs back in the ​’70s were a technology ahead of their time. We have the opportunity to seize on all that advancement and turn it into a truly perfect commercial product that is safely operated throughout the world.”

X-energy still faces the challenge of proving that it can avoid the hiccups previous high-temperature gas-cooled units faced in operation. Water-cooled reactors run at an unrivaled 95% of their lifespans in part because operators have the most experience perfecting the art of piloting such plants.

But Taylor compared earlier versions of high-temperature gas-cooled reactors to one of the American automotive industry’s biggest flops of the mid-20th century.

“The technologies between 50 years ago and today are both nuclear reactors, but it’s an Edsel-to-a-Ferrari comparison,” he said. ​“In this Ferrari, we know what we need to design for to get maximum performance out of it, we know what the challenging pieces are, what the hard issues are. Will we learn things? Sure, but we have so much more knowledge than those first ones did that we’re designing out so many of the challenges they faced.”

Alexander C. Kaufman is a contributing reporter at Canary Media, and an award-winning writer who has covered energy and climate change for more than a decade.