NRC approves construction permit for Dow and X-energy's four-reactor Long Mott plant in Texas

The US Nuclear Regulatory Commission (NRC) has approved a permit to build the proposed Long Mott Generating Station, a four-reactor nuclear plant at Dow's Seadrift Operations in Texas, Dow and X-energy announced on 9 November. The US Department of Energy's Office of Nuclear Energy gives 9 November as the approval date in a post of 13 November, while the NRC's project page records its permit decision on 8 November.

Dow says its wholly owned subsidiary Long Mott Energy, LLC is developing the project in partnership with X-energy, under the Department of Energy's Advanced Reactor Demonstration Program. The department says the plant would use four of X-energy's Xe-100 small modular reactors, which would supply high-temperature steam and electricity to manufacturing at Seadrift. It says each unit is designed for 80 MW of electricity or 200 MW of thermal output, and that together the four could deliver up to 320 MW of electricity while meeting industrial steam demand at the site over 60 years. Dow says the plant would replace power and steam equipment at the site that is close to the end of its working life. The NRC's project page puts the plant on about 1,537 acres next to Seadrift Operations, in Calhoun County, and gives 31 March 2025 as the date the application was filed.

The Department of Energy says the approval is the first construction authorisation for an advanced nuclear facility at a US industrial site, the first permit the NRC has issued to build a gas-cooled, high-temperature reactor in over 50 years, and the NRC's first approval of a pebble-bed design for a reactor core. It describes the Xe-100 as a gas-cooled reactor operating at high temperature and running on TRISO-X, a coated-particle fuel made with high-assay low-enriched uranium (HALEU).

X-energy says the permit completes both the safety review and the environmental review by the NRC, and that the review found the Xe-100 can be sited and built safely within an industrial site that is already operating. It quotes NRC Chairman Ho K. Nieh as saying the agency met its 18-month schedule. The NRC's project page lists a hearing on 22 September 2026 and an environmental assessment, issued on 18 May 2026, that found no significant impact.

The Department of Energy says the permit lets X-energy and Dow move the project toward readiness for construction: finishing the Xe-100 design, securing supply of long-lead components, and drawing up an application for an operating licence, which the NRC would then review. Dow says the permit is not a final decision to build. It says milestones remain, among them further engineering and design work and a review by its board of directors, and that if the project is approved, building could start later this decade and the plant could start up early in the next. X-energy says Dow is due to weigh a preliminary investment decision during 2027, and that full-scale construction would come once Dow takes its final investment decision. The Department of Energy says the project is aiming for first energy in the early 2030s.