US clears first high-temperature gas reactor in 60 years for four-unit Texas plant

Artist’s rendering of X-energy’s Xe-100 SMR.X-EnergyKey TakeawaysThe NRC has issued a construction permit for four Xe-100 reactors at Dow's Texas industrial site.The 320 MWe facility will primarily supply high-temperature steam, with surplus electricity exported to the grid.The approval marks the first construction permit for an HTGR in nearly 60 years, but a separate operating licence is still required. The US Nuclear Regulatory Commission (NRC) has issued a construction permit for a four-reactor nuclear power facility in Texas, marking the first approval for a high-temperature gas-cooled reactor (HTGR) in nearly 60 years. The Long Mott Generating Station, planned for Calhoun County, Texas, will feature four Xe-100 small modular reactors (SMRs) developed by US-based X-energy. The project is being developed by Long Mott Energy, a wholly owned subsidiary of chemical manufacturer Dow, for its Seadrift Operations site. The facility is designed primarily to supply high-temperature steam for industrial processes at Dow’s site. It will also generate electricity, with surplus power exported to the grid. The construction permit marks a significant milestone for advanced nuclear technology in the US. It is the third advanced reactor construction permit issued by the NRC in 2026 and the agency’s first approval of a multi-module advanced reactor facility. Four reactors supply industrial steam The four Xe-100 reactors will have a combined thermal capacity of 800 megawatts (MWth) and an electrical capacity of 320 megawatts (MWe). Each module is designed to generate approximately 80 MWe of electricity while also supplying heat for industrial applications. Unlike conventional nuclear power plants that primarily generate electricity, the Long Mott facility is designed around the energy requirements of an industrial site. High-temperature steam can support energy-intensive manufacturing operations, potentially replacing conventional fossil-fuel-based heat sources. The Xe-100 is a high-temperature gas-cooled reactor that uses helium as a coolant and graphite pebbles containing tri-structural isotropic (TRISO) fuel particles. Its pebble-bed core allows fuel to be added during operation, rather than requiring the reactor to shut down for conventional refueling. The NRC’s approval also marks several regulatory firsts. These include its first construction permit for a pebble-bed reactor, its first approval of a reactor design featuring online refueling, and its first review of an HTGR under its risk-informed, technology-inclusive Licensing Modernization Project framework. Permit clears construction path The NRC completed its comprehensive safety evaluation in October, ahead of its scheduled timeline. It had already issued an Environmental Assessment and Finding of No Significant Impact in May. The agency said its review was completed within an 18-month schedule, demonstrating its ability to assess advanced reactor designs while maintaining its safety requirements. “Today, the new NRC is issuing America’s first construction permit for a high-temperature gas-cooled reactor in more than half a century,” NRC Chairman Ho K. Nieh said. The permit authorizes Long Mott Energy to construct the facility in accordance with the approved design. However, it does not allow the company to load nuclear fuel or operate the reactors. A separate operating license from the NRC will be required before the plant can begin generating power. Dow has also clarified that receiving the permit does not constitute a final investment decision to proceed with construction. The company still needs to complete engineering and design work and secure approval from its board. If it proceeds, construction could begin later this decade, with the facility expected to start operating in the early 2030s. The project is being developed under the US Department of Energy’s Advanced Reactor Demonstration Program, which supports the development and deployment of next-generation nuclear technologies.Get the latest in engineering, tech, space & science - delivered daily to your inbox.With over a decade-long career in journalism, Neetika Walter has worked with The Economic Times, ANI, and Hindustan Times, covering politics, business, technology, and the clean energy sector. Passionate about contemporary culture, books, poetry, and storytelling, she brings depth and insight to her writing. When she isn’t chasing stories, she’s likely lost in a book or enjoying the company of her dogs.