Nov 8, 2025

A closeup of one of the 16 TRISO-X fuel pebbles undergoing testing at Idaho National Lab.US DOE X-energy has launched a critical 13-month test of its advanced TRISO-X nuclear fuel at the Idaho National Laboratory (INL). This is the first time the company’s “fuel pebbles” will undergo irradiation testing in a US lab, a milestone for the next generation of nuclear reactors. The experiments at INL’s Advanced Test Reactor are an essential step in securing approval from the US Nuclear Regulatory Commission (NRC). This approval is required to deploy advanced reactors, like X-energy’s Xe-100, that rely on this new fuel design. New standard in fuel safety The TRISO-X fuel is designed for high-temperature gas-cooled reactors . Its particles contain a uranium kernel wrapped in three layers of carbon and ceramic materials. This protective structure prevents the release of radioactive fission products and, according to the company, makes the fuel incapable of melting in a reactor. “TRISO-X embodies decades of US innovation in fuel design,” said J. Clay Sell, CEO of X-energy. He stated this testing program “brings us one step closer to redefining the standard for safety and reliability in nuclear energy.” During the test, the fuel will be exposed to various power levels, temperatures, and burnup conditions to simulate a wide range of operating scenarios. Powering commercial deployment This fuel qualification is central to X-energy’s broader commercial strategy. The company is currently building the TX-1 fuel fabrication facility in Oak Ridge, Tennessee, which could become the first NRC-licensed advanced nuclear fuel facility in over 50 years. The TX-1 facility will produce the fuel for the company’s Xe-100 small modular reactor (SMR). The first Xe-100 units are planned for Dow’s manufacturing site in Seadrift, Texas, to provide power and high-temperature heat for industrial use. X-energy is also working with Amazon and Energy Northwest on a plan to build up to 12 SMRs near the Columbia Generating Station in Washington state. Dan Wachs, a National Technical Director for the DOE’s Advanced Fuels Campaign, called the experiment “a huge one for supporters of advanced nuclear.” “The test marks INL’s first irradiations of TRISO fuel for advanced reactors since 2020 and the first use of a new lead-out test capability at ATR that makes these advanced fuel tests possible,” he added . After the 13-month irradiation cycle at INL, the fuel will undergo further post-irradiation examination at both INL and Oak Ridge National Laboratory to complete its journey toward commercial use. Related developments In a related move to support the advanced reactor market, US-based Standard Nuclear Inc. and French nuclear giant Framatome have joined hands for the formation of a joint venture. The new entity, named Standard Nuclear-Framatome (SNF), aims to supply commercial-scale quantities of Tri-structural Isotropic (TRISO) fuel for the next generation of nuclear reactors. SNF’s goal is to meet the growing demands of the advanced reactor market, including small modular reactors (SMRs) and micro-reactors. The partnership plans to commence manufacturing at Framatome’s Richland, Washington facility in 2027, pending regulatory approvals. Recommended Articles