Long Mott: X-energy Says NRC Issued Final Safety Evaluation, 320 MWe

The US Nuclear Regulatory Commission (NRC) has issued its final safety evaluation for the Long Mott Generating Station, Dow's planned four-module, 320 MWe Xe-100 plant at Seadrift, Texas, reactor developer X-energy said on Oct. 30.

According to the company's statement, the report records the NRC staff's finding that the plant and its site give a safety basis to start construction under 10 CFR Part 50. X-energy added that the Advisory Committee on Reactor Safeguards, a panel of outside experts that advises the Commission, reviewed the staff's work separately and supports issuing the construction permit. The NRC had issued no news release on it by Oct. 30, and its project page, last updated Sept. 14, still lists the final safety evaluation as a November 2026 target.

The step clears the milestone our Oct. 28 project file on Long Mott named as the next one, and it came before the NRC's own target. With the environmental assessment and finding of no significant impact issued on May 18, 2026, both main technical reviews are now finished, X-energy said. What remains, X-energy says, is the final stage of the construction permit review; the NRC's project page lists both a hearing and the construction permit decision as TBD.

What a Long Mott Construction Permit Would Allow

A construction permit lets the owner build; it does not let the plant run. Long Mott Energy, the Dow subsidiary that applied on March 31, 2025, would still need an operating licence before the reactors could start. Each Xe-100 module is a high-temperature gas-cooled reactor fuelled by TRISO particles in graphite pebbles and can deliver 80 MWe of electricity or about 200 MWt of steam, according to the NRC. The plant, rated 800 MWt and 320 MWe, would feed power and steam to Dow's adjacent Seadrift Operations. X-energy says the design supports a 400-meter emergency planning zone, against 10 miles for conventional light-water reactors, and that this allows siting inside the perimeter of a large industrial facility.

Why Long Mott Matters for Other Xe-100 Buyers

Long Mott is the first Xe-100 to reach this point, and X-energy says the review sets precedents for later Xe-100 applications, though each will be reviewed on its own. That matters for the buyers queued behind it. Amazon backs Energy Northwest's Cascade project in Washington, whose permit filing has slipped to the first half of 2027, and funds a study of a 960 MW, 12-module Xe-100 plant in Indiana with AEP. Neither has a permit application before the NRC.

What Comes Next for the Long Mott Permit

The NRC had scheduled a mandatory hearing for Sept. 22 in Port Lavaca, Texas, according to a Sept. 14 agency advisory, with written comments due by Oct. 6. That date has passed, and the documents we read do not say whether the hearing was held or what followed; the project page still lists the hearing and the permit decision as TBD, and the agency has given no decision date. At TerraPower's Kemmerer Unit 1, the NRC finished its final safety evaluation in December 2025 and announced on March 4, 2026 that it had approved the construction permit, which ANS Nuclear Newswire called the first NRC approval of a commercial non-light-water reactor in more than 40 years.

Other questions are open. An NRC licensing board admitted a local environmental group's challenge to Long Mott Energy's financial qualifications in January 2026, ANS reported, but X-energy's quarterly filing says the board later granted Dow's motion to dismiss and terminated the proceeding in June 2026. Dow has not announced a decision to build. X-energy's own risk statement names the permit, Dow's choice whether to proceed and project financing, and its Oct. 30 statement gave no cost or first-power date.