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The NRC construction permit for Long Mott lets Dow and X-energy build a 320 MWe, four-unit Xe-100 plant at Seadrift, Texas, but not run it. Dow expects to consider a preliminary investment decision in 2027.
Chips & Power DeskEdited by Ege Erten
3 min readAI-assisted
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Rendering of the Xe-100 reactor design that Dow and X-energy plan to build at Long Mott; not a photo of the Seadrift site.
Image: X-energy
Source · Press image from the X-energy website, used for news reporting.
The U.S. Nuclear Regulatory Commission (NRC) issued a construction permit on Nov. 9 for Long Mott Generating Station, four X-energy Xe-100 reactors of 80 MWe each at Dow's Seadrift Operations site in Calhoun County, Texas, Dow and X-energy said.
The permit comes 10 days after the NRC's final safety evaluation of the plant, as Voltgrid reported on Oct. 30, and the companies say it completes the regulator's safety and environmental reviews. Our Long Mott project file set out the plant: four modules rated 800 MWt, or 320 MWe, in total according to the NRC's project page, built to supply both electricity and high-temperature steam to a chemical site. The NRC is no longer the open question. Dow's investment decision is.
The NRC's news index lists the decision as release 26-083, titled "NRC Issues First Construction Permit in Nearly 60 Years for High-Temperature Gas-Cooled Reactor". The release itself was not available on the NRC website on Nov. 9, and the agency's Long Mott project page had not been updated since Sept. 14, so the permit details here come from the companies' joint statement. It quotes NRC Chairman Ho K. Nieh as saying the agency met its 18-month review schedule. Long Mott Energy, the Dow subsidiary that holds the application, filed it on March 31, 2025, according to the NRC.
Under the NRC's two-step Part 50 process, a construction permit lets the owner build; it does not let the plant run. Long Mott Energy still needs a separate operating licence, and the companies say they will now develop that application for the NRC. They gave no filing date. The NRC's review found the Xe-100 can be sited and built inside an operating industrial plant, according to the companies. Each Xe-100 is a helium-cooled, pebble-bed high-temperature gas-cooled reactor rated 80 MWe and 200 MWt, and X-energy expects the design to support a 400-meter emergency planning zone, against 10 miles for conventional light-water reactors. That expectation is the company's.
The permit is also not a decision to build. Dow expects to consider a preliminary investment decision in 2027, and full-scale nuclear construction would start only after its final investment decision, the companies said. Edward Stones, Dow's business vice president for energy and climate, said Dow will weigh competitiveness, execution readiness and capital affordability before any decision on construction. Until then the work is finishing the design and ordering long-lead parts: X-energy placed the first Xe-100 steam generator tubing order for Long Mott on Nov. 4, as Voltgrid reported. First delivery is still targeted for the early 2030s, and the plant is meant to serve the Seadrift site for 60 years.
The construction permit is done; the operating licence application has no date, and Dow's 2027 decision and early-2030s delivery are targets.
Illustration (AI-generated)
That sets Long Mott apart from the other plant in the Department of Energy's Advanced Reactor Demonstration Program to hold a permit. The NRC authorized staff to issue the construction permit for TerraPower's Kemmerer Unit 1 in Wyoming on March 4, 2026, and TerraPower announced the start of construction on April 23.
Amazon is not a party to Long Mott. Its Xe-100 projects, Energy Northwest's Cascade plant in Washington, which is proposed and at the pre-application stage, and a proposed 12-unit plant in Indiana that X-energy and AEP are assessing under a joint development agreement, do not hold construction permits, and the Seadrift permit gives them no licence of their own. X-energy chief executive J. Clay Sell said the permit came earlier than expected and validates an approach the company can repeat across its pipeline, a company claim that later reviews will test. As Voltgrid argued on Nov. 1, a finished NRC review of the Xe-100 lowers design risk for Amazon's plans more than it lowers project risk at its own sites.
San Antonio Bay Estuarine Waterkeeper asked the Commission on July 20, 2026, to review licensing board rulings that dismissed its contentions on the project as moot, and Long Mott Energy filed an answer opposing the petition. Voltgrid found no Commission ruling on that petition in NRC records, and the companies' statement does not mention it. Next on the calendar are X-energy's third-quarter results on Nov. 12, listed in our week ahead, and Dow's preliminary investment decision, expected in 2027.
