Advanced reactor developer X-energy and global materials science company Dow have submitted a construction permit application (CPA) to the U.S. Nuclear Regulatory Commission (NRC) for a first-of-its-kind small modular reactor (SMR) project at Dow’s Union Carbide Corp. (UCC) Seadrift Operations in Calhoun County, Texas. The filing marks a major step forward for the much-watched commercial-scale advanced nuclear project in the U.S.—now formally named Long Mott Generating Station.
The proposed project being developed by Dow’s wholly owned subsidiary Long Mott Energy will comprise four Xe-100 high-temperature gas-cooled reactors (HTGRs), which means the power plant will have a combined capacity of 320 MWe/800 MWth. First announced in May 2023, the project is envisioned to demonstrate how advanced nuclear technology can directly decarbonize large-scale industrial operations by supplying both electricity and high-temperature steam to Dow’s sprawling 4,700-acre Seadrift site, which produces more than four billion pounds of chemical products annually.
If approved and built, Long Mott would become “the first grid-scale advanced nuclear reactor deployed to serve an industrial site in North America,” X-energy and Dow said in a statement on March 31. For Dow, the project is expected to eliminate most Scope 1 and Scope 2 greenhouse gas emissions from the site, aligning with the chemical firm’s broader sustainability goals while ensuring long-term competitive advantages for its operations.
The project is backed by the U.S. Department of Energy’s Advanced Reactor Demonstration Program (ARDP), which in 2020 awarded X-energy $80 million in initial funding as part of a larger commitment to support advanced nuclear deployment. Under the program’s cooperative agreement, the DOE has indicated it could invest up to $1.23 billion over seven years to support the licensing, construction, and demonstration of the Xe-100 reactor and its associated TRISO-X fuel fabrication facility. Originally slated for development with Energy Northwest in Washington state, the project shifted in 2023 when Dow became X-energy’s official sub-awardee and end-user, repositioning the demonstration at the Seadrift site.
While the NRC is readying to make the CPA public, X-energy told POWER that acceptance and review of the construction permit could take up to 30 months, which would put construction on track to begin later this decade, with operations potentially beginning in the early 2030s. Daniel Womack, Dow’s global lead for Carbon Policy, at the PowerGen conference in February suggested the operational timeframe is likely 2031 to 2032.
Asked how the timing shift aligns with the ARDP schedule—which sought an operational target date in 2027/2028—Robert McEntyre, spokesperson for X-energy, told POWER on Monday that Dow is “evaluating the project through its rigorous technical and feasibility gate review process.” He noted the process is standard for all Dow’s power generation and megaprojects. “Throughout this process, we’ve been working to align the milestones of the gate review with the programmatic milestones of ARDP,” he added. “DOE has been agreeable to this alignment, and we believe this partnership with a proven project delivery organization provides the program with the best opportunity to be successful.”
A Major Milestone for Industrial Nuclear
Long Mott’s CPA submission for an advanced nuclear project under the NRC’s Part 50 marks a notable first for an industrial firm seeking to replace aging energy and steam assets with cutting-edge nuclear technology. “The energy assets [at the Seadrift site] are approaching their end of life, which is one of the reasons we turned to the SMR project,” Womack explained in February. “When we look at building out new assets, they need to last 20, 30, 40 years. It’s got to be something reliable, cost-competitive, and clean.”
While not the first, the Long Mott licensing application marks another key milestone in a growing wave of advanced nuclear momentum. Since 2023, similar CPAs have been filed separately by Kairos Power for a molten salt demonstration reactor in Tennessee, Abilene Christian University for its Molten Salt Research Reactor (MSRR) in Texas, and TerraPower, another ARDP award winner, for Kemmerer Unit 1, a 345-MW Natrium sodium-cooled fast reactor (SFR) power plant that is under construction in Wyoming
But for X-energy, Long Mott will serve more than a demonstration. It will showcase a commercial deployment of the Xe-100 with a real customer, a defined industrial use case, and long-term economic implications. “We believe it demonstrates real progress, not just potential,” said McEntyre.
Long Mott will also serve as a crucial proving ground for X-energy’s broader commercial ambitions—particularly in partnership with a growing field of potential commercial and industrial power consumers, including hyperscalers. In October 2024, Amazon announced it would support the deployment of up to 5 GW of X-energy’s Xe-100 SMRs by 2039, including through direct investments and long-term power purchase agreements. That deployment is set to begin with an initial 320-MWe Xe-100 plant in central Washington with Energy Northwest, a regional utility consortium. Amazon is funding early development work for that site, with options to expand to as many as 12 reactor units.
Amazon’s investment in X-energy also includes $500 million in Series C-1 financing, alongside commitments from Citadel’s Ken Griffin, Ares Management, NGP, and the University of Michigan. The capital is expected to help advance X-energy’s Xe-100 design, licensing work, and the first phase of its TRISO-X fuel fabrication facility in Oak Ridge, Tennessee. X-energy on Monday noted it has already secured $1.1 billion in private capital since being selected by DOE in 2020 for its ARDP award. The company says it has so far completed engineering and preliminary design work for its Xe-100 reactors and made progress on the TRISO-X fuel fabrication facility.
“We were founded on the principle that nuclear energy has the most promise and opportunity when delivered at scale. Our partnerships with DOE, Dow, Amazon, among others, put us in a better position to realize that vision for all our customers,” McEntyre said. “ARDP has been essential in adding credibility and providing momentum for X-energy’s technologies, helping build the gateway for our subsequent projects and customers (including our 5 GW target for deployments in partnership with Amazon). Ultimately, this helps to establish the market for commercial reactors that are safe and affordable to construct and operate, fulfilling a core objective of ARDP.”
Long Mott’s financial structure will be managed through Dow, supported by milestone-based cost-sharing under the DOE’s Advanced Reactor Demonstration Program (ARDP). While X-energy has not disclosed specific cost figures, McEntyre said, “Small modular nuclear power is expected to be cost-competitive with alternatives that could support both Dow’s power and steam needs and its carbon emissions reduction targets.”
Fuel Supply and the TRISO-X Plant
While Long Mott takes shape, X-energy also developing the first phase of its TRISO-X fuel fabrication facility in Oak Ridge, Tennessee, where X-energy will manufacture its proprietary tri-structural isotropic (TRISO) particle fuel, TRISO-X. The TRISO-X fuel requires high-assay low-enriched uranium (HALEU)—a specialized nuclear material that is not yet commercially available in the U.S.
According to McEntyre, the DOE is slated to provide HALEU for the first Xe-100 core load at Long Mott under ARDP and has awarded contracts for enrichment service providers to help spur the development of this critical supply chain. “This program, and its progress, have been key factors in helping our customers, Dow and Amazon included, move ahead with Xe-100 projects,” he noted. “In addition, we plan to complete site prep at our TRISO-X fuel fabrication facility in Oak Ridge, Tennessee, by this summer, with plans to begin vertical construction later this year.”
X-energy broke ground on the TRISO-X facility—formally named TX-1—in October 2022, and in December 2024, it awarded a $40.8 million contract to Geiger Brothers for the site development phase, which is expected to be completed by July 2025. Located on a 110-acre campus in Oak Ridge’s Horizon Center Industrial Park, the 215,000-square-foot facility will be the first commercial-scale plant in North America dedicated to fabricating TRISO fuel for advanced reactors.
Supported by both the ARDP and a $148.5 million Inflation Reduction Act tax credit, TX-1 is designed to produce up to 714,000 fuel pebbles per year and create approximately 400 permanent jobs. X-energy has also submitted a license application to the NRC to possess and use special nuclear material, and the review is now nearly halfway complete. The company says TRISO-X fuel from this facility will support initial Xe-100 deployments in the U.S. and abroad.
—Sonal Patel is a POWER senior editor (@sonalcpatel, @POWERmagazine).
