X-energy’s Long Mott nuclear plant in Texas moved to its final permitting stage

The Nuclear Regulatory Commission closed the safety half of its review of the Long Mott project on October 30, releasing the Final Safety Evaluation Report for four X-energy Xe-100 reactors planned on the Texas Gulf Coast. Both of the agency’s primary reviews, safety and environmental, are now finished. What remains is the commission’s decision on a construction permit.

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The reactors would sit at Dow’s Seadrift Operations in Calhoun County and total 800 MWt, or 320 MWe. If the permit is granted, Long Mott would be the first grid-scale advanced reactor built at an industrial facility in the United States, according to X-energy.

From the March 2025 filing to the October 30 report

Long Mott Energy, a wholly owned subsidiary of The Dow Chemical Company, applied for the construction permit on March 31, 2025. World Nuclear News reported on November 2 that the Final Safety Evaluation Report concludes the proposed plant and site provide a safety basis to begin construction, and that the NRC has told followers to expect a construction permit announcement soon.

The NRC’s Long Mott project page, last updated September 14, lays out the sequence. The application was docketed on May 12, 2025, a draft safety evaluation followed in February 2026, and an advanced version with all sections available to the Advisory Committee on Reactor Safeguards came in August 2026. At that update the final report was still targeted for November, so its release on October 30 came slightly ahead of the date the page listed.

The same page lists the mandatory hearing and the permit decision as “TBD.” No date for either appears in the sources read for this article, and the absence of one is the main uncertainty left in the schedule.

An environmental assessment instead of a full impact statement

The environmental track finished first. On May 18, 2026, the agency issued an Environmental Assessment and a Finding of No Significant Impact, which spared the project a full environmental impact statement. POWER magazine’s coverage says X-energy described it as the first U.S. commercial advanced reactor project in a Part 50 construction permit proceeding to clear environmental review through an assessment alone. Mike King, the NRC’s executive director for operations, said the assessment reflects the project’s relatively low potential for environmental impacts and offers a more predictable path.

The choice rested on the setting. The NRC said an assessment better addresses the project’s limited footprint at an existing industrial location, and X-energy cautioned that a site with different characteristics could still need the longer document. Dow’s announcement of the finding adds that the review ran under a year, covered air quality, water resources and local habitats, and drew on a report of more than 1,000 pages, a year of field surveys and 12 months of groundwater data.

Four Xe-100 units and the Seadrift steam demand

The Xe-100 is a helium-cooled, high-temperature gas reactor that uses TRISO fuel and can produce heat up to 600 degrees Celsius. Each of the four modules is rated at 80 MWe, which is how the plant reaches 320 MWe. According to the American Nuclear Society’s account, the reactors would supply electricity and high-temperature steam to the chemical plant, and the project is one of two demonstrations backed by the Department of Energy’s Advanced Reactor Demonstration Program. The other, TerraPower’s Natrium plant in Wyoming, began construction in April 2026.

Dow says the steam will support production of more than 4 billion pounds of materials a year at Seadrift, with surplus electricity going to the grid. Dow’s release adds that the helium coolant does not become radioactive in operation and that the design needs neither cooling towers nor water intake structures. X-energy’s engagement with the agency on the design reaches back to 2018, and the Seadrift application is the first high-temperature gas-cooled reactor construction permit request under the NRC’s technology-inclusive, risk-informed, performance-based licensing framework. Dragan Popovic, X-energy’s chief global operating officer, said licensing a new reactor is earned through the quality of the application and the rigor of the regulator’s review, and described the completed safety review as the product of years of work by X-energy and NRC staff.

A construction permit would not let the plant run. An operating license is still required before fuel loading, and ANS reported in May that Dow does not expect a final investment decision before 2028. No timeline for the operating license application or commercial operation has been disclosed.

The NRC is working under an 18-month review limit set by Executive Order 14300, according to X-energy, and the agency has hit its own interim targets so far. Edward Stones, Dow’s business vice president for energy and climate, called the environmental finding a significant milestone for the project and said it brings the company a step closer to expanding access to safe, clean, reliable, cost-competitive nuclear energy. The open question now is when the agency will schedule the mandatory hearing and announce its permit decision, since neither date has been published.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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