X-energy

X-energy was founded in 2009 in Rockville, Maryland by Kam Ghaffarian, a serial entrepreneur who also founded Stinger Ghaffarian Technologies (SGT), a major NASA contractor. Ghaffarian spotted an opportunity in the DOE’s Next Generation Nuclear Plant (NGNP) program, which had been developing high-temperature gas reactor technology through the 2000s but never reached commercialization. He recruited talent from the NGNP program and related TRISO fuel research programs to form X-energy’s founding technical team, including pebble-bed HTGR experts with decades of combined experience. Clay Sell, former Deputy Secretary of Energy under President George W. Bush, was appointed CEO in 2019. Harlan Bowers serves as President.

X-energy’s Xe-100 is a 76 MWe (200 MWt) high-temperature gas-cooled reactor (HTGR) using pebble-bed fuel architecture. The reactor’s fuel — called TRISO-X — consists of poppy-seed-sized uranium kernels coated in multiple layers of ceramic material, embedded in graphite spheres (“pebbles”) that continuously circulate through the reactor core. The ceramic TRISO coating acts as a microscopic pressure vessel, physically preventing the release of fission products under any accident scenario. The reactor is cooled by pressurized helium, which is chemically inert and cannot become radioactive. The Xe-100 is designed to be walkaway safe without operator intervention: if power is lost entirely, the reactor passively shuts down and cools itself through conduction and radiation alone. Because pebble-bed reactors are refueled continuously (spent pebbles are removed and fresh ones added daily), the Xe-100 never needs to shut down for refueling — enabling very high capacity factors.

X-energy received up to $1.2 billion in cost-shared funding from the DOE’s Advanced Reactor Demonstration Program in 2020. In October 2024, Amazon led a $500 million Series C-1 investment round (expanded to $700 million in February 2025) alongside Amazon as an anchor investor, with Citadel’s Ken Griffin, Dow Inc., and other industrial partners. The company has approximately 600 employees.

X-energy’s primary commercial project is a four-reactor (4×76 MWe) Xe-100 plant at Dow Inc.’s petrochemical manufacturing site in Seadrift, Texas, replacing existing natural gas turbines with nuclear-generated heat and electricity. This project, awaiting an NRC construction permit submitted in March 2025, would be the first commercial HTGR in US history and the first-ever nuclear plant to directly supply industrial process heat to a chemical manufacturer. X-energy is building a TRISO-X fuel fabrication facility in Oak Ridge, Tennessee. Amazon has committed to deploy over 5 GW of nuclear capacity across the US by 2039, with X-energy as a key partner.