US issues landmark construction permit for Texas SMR plant

The plant, known as the Long Mott Generating Station, is being developed through Dow's wholly owned subsidiary, Long Mott Energy, in collaboration with X-energy under the US Department of Energy's Advanced Reactor Demonstration Program (ARDP). 

Industrial giant Dow signed a joint development agreement with reactor developer X-energy in 2023. In March 2025, the company, alongside other major energy users, signed a pledge supporting the goal of at least tripling global nuclear capacity by 2050. Later that month, the construction licence application for the plant was submitted to the Nuclear Regulatory Commission (NRC).

Dow has not yet made a final decision to proceed with construction of the proposed facility: before potential construction activities could begin, further milestones including continued engineering and design finalisation and review by Dow's Board of Directors must be completed. But if approved, construction could begin later this decade, with startup early next decade, the company said. The company is expected to consider a preliminary investment decision in 2027. 

The construction permit authorises the facility to be built, but does not authorise operation: a separate operating licence will be needed before the reactors can be fuelled or operated. However, the companies said, this means they can also work on maturing the supply chain for long-lead components and materials, as well as on their operating licence application. Ensuring the design, equipment, and materials are in place before allocating major capital for full-scale construction is consistent with Dow's global project management practices, and, for a first-of-a-kind project, reduces schedule and cost risk once work begins on site.

The NRC completed its safety review for the plant when it released its Final Safety Evaluation Report for the construction permit application on 30 October. X-energy CEO Clay Sell said the construction permit had been received earlier than expected, thanks, in part, to "thorough and efficient" work by the NRC plus Congressionally-mandated reforms put in place over the past six years. "This milestone is further validation of the XE regulatory approach that can be replicated across our growing commercial pipeline, giving our customers greater confidence in the regulatory process and a clearer path to deployment," he said.

Edward Stones, business vice president, Energy & Climate at Dow, described the issuance of the construction permit as a "testament to the thoughtful, thorough and efficient review conducted by the NRC", appreciating the regulator's commitment to maintaining the highest safety standards while advancing a clear and predictable regulatory process for advanced nuclear technologies. "As we move forward, we will continue to evaluate the project through the lens of competitiveness, execution readiness, and capital affordability before any decision regarding construction is made," he said.

_{A rendering of the plant (Image: X-energy)}

Regulatory firsts

X-energy's Xe-100 is an 80 MWe/200 MWt high-temperature gas-cooled reactor which uses advanced TRISO-X coated particle fuel. The passive physics of the fuel - with the coating in effect providing each fuel particle its own containment for fission products which is stable up to very high temperatures - gives it a safety profile expected to support a 400-metre emergency planning zone, compared with 10 miles (16 kilometres) for conventional light-water reactors, enabling new generation to be safely sited closer to the point of need.

The proposed Long Mott plant is intended to provide both electricity and high-temperature steam to Dow's Seadrift site, replacing existing energy and steam assets near their end-of-life and providing clean industrial power to the site for 60 years and is expected to be the first advanced nuclear project deployed at an industrial site in North America.

The construction permit also marks several regulatory firsts for the NRC: its first approval of a multimodule advanced reactor facility; its first approval of a reactor with a pebble-bed core; its first approval of a design featuring online nuclear refuelling; and its first review of a high-temperature gas-cooled reactor under the agency's risk-informed, technology-inclusive Licensing Modernisation Project framework.

"Today, the new NRC is issuing America's first construction permit for a high-temperature gas-cooled reactor in more than half a century," NRC Chairman Ho K. Nieh said. "We delivered on the 18-month schedule, proving we can do rigorous safety reviews on predictable timelines that move advanced nuclear technology from design to construction."