NRC issues construction permit for Dow/X-energy Long Mott project

The Nuclear Regulatory Commission has approved Dow's construction permit application for its Long Mott Generating Station in Seadrift, Texas, which would include four X-energy Xe-100 reactors.

Monday's construction permit issuance for the 320-MWe reactor project at Dow's UCC Seadrift Operations manufacturing site is historic on multiple fronts:

• It is the first construction permit issued for a high-temperature, gas-cooled (HTGR) reactor in nearly 60 years.
• It is the first-ever U.S. approval for a pebble-bed HTGR design.
• It is the first time the NRC has issued a construction permit for a nuclear reactor on an industrial site.

"This is an important day. Getting the construction permit earlier than expected is reflective of the thorough and efficient work of the NRC, the reforms that have been put in place by Congress over the last six years, and the phenomenal work of the X-energy and Dow teams," said X-energy CEO Clay Sell.

About the project: Dow has proposed to construct four Xe-100s, an 80-MWe, 200-MWt HTGR that can be deployed in configurations of four to 12 units. As a pebble-bed HTGR, the Xe-100 would be fueled by HALEU TRISO particles encased in graphite pebbles and cooled by helium.

An HTGR produces steam at high temperatures that can be used for electricity production or for industrial purposes. Dow and X-energy have noted this project would do just that, providing both electricity and high-temperature steam. According to the two companies, Long Mott could replace existing energy and steam assets at Seadrift that are nearing their respective ends of life. The four reactors are expected to provide power to the site for 60 years.

Seadrift-Dow's second-largest site in Texas-produces everyday consumer products like plastics (polyethylene) for wire and cable applications, food and beverage containers, automotive parts, toys, and diapers; glycols for antifreeze, polyester fabrics, and bottles; and oxide derivatives for health and beauty products.

A construction permit alone does not mean that the Long Mott project is moving forward. Both Dow and X-energy have said a final decision hasn't been made yet. "Several important milestones remain before potential construction activities could begin, including continued engineering and design finalization and review by Dow's Board of Directors," the Dow announcement said.

A preliminary investment decision is expected in 2027. If approved, construction could begin later this decade, with commercial operation in the early 2030s. The NRC would need to issue an operating license for fuel loading and start-up.

Long time coming: The permit was issued to Dow's wholly owned subsidiary, Long Mott Energy. The project-a collaboration with X-energy-is part of the Department of Energy's Advanced Reactor Demonstration Program (ARDP). It is one of two full-scale demonstration projects under ARDP, the other being TerraPower's Natrium power plant project in Wyoming, which received its construction permit earlier this year. The Seadrift project has received roughly $2.15 billion in cost-shared funding from DOE.

The construction permit milestone comes roughly six years after the DOE picked X-energy for the ARDP. While X-energy originally planned to site its ARDP demo near Richland, Wash., and remains engaged with Energy Northwest and Amazon on the planned Cascade Advanced Energy Facility, in 2023 the company entered into an agreement with Dow to build the ARDP demo plant at a Dow site. In the spring of 2025, Long Mott Energy submitted a construction permit application and the NRC docketed the application soon after. The most recent regulatory hurdle the project cleared came this spring, when the NRC completed its environmental assessment of the proposed facility and issued a finding of no significant impact.

Monday's issuance means a permit decision was reached within 18 months of the review commencing, a target NRC officials set for the process.

"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," said NRC Chairman Ho Nieh.

It is the third construction permit issued by the NRC in 2026, following the Natrium plant permit issuance in March and the September approval of a GE Vernova Hitachi BWRX-300 at the Clinch River site in Oak Ridge, Tenn.