The fuel of the future is already here: Why TRISO matters

Amazon is investing in next-generation nuclear technology that uses tristructural isotropic (TRISO) fuel particles, which are more robust and safer than traditional reactor fuel, the company detailed in a technical overview [1]. Each TRISO particle is about the size of a poppy seed and contains a kernel of enriched uranium surrounded by a ceramic shell [1]. The shell includes a silicon carbide layer that acts as a pressure vessel and chemical barrier, with a melting point above 2700°C [1]. Data from the U.S. Department of Energy's Advanced Gas Reactor Fuel Qualification Program show that irradiated TRISO particles subjected to 1600°C for 300 hours exhibited an upper-bound failure fraction of ≤ 6.6 × 10⁻⁵, and at 1800°C failure rates remained well below conservative design limits [1]. The proven durability of the coatings preserves long-term stability in spent fuel, potentially for as long as 100,000 years [1]. TRISO particles are manufactured using high-assay low-enriched uranium (HALEU), enriched to between 10% and 20% ²³⁵U [1]. The higher energy density supports compact, high-output designs. Amazon is backing the Xe-100, a pebble-bed high-temperature gas-cooled reactor developed by X-energy, a publicly traded nuclear engineering company headquartered in Rockville, Maryland [6]. Each Xe-100 unit produces 80 megawatts of electricity, and up to 12 can be collocated [1]. The deployment is centered on the Cascade Advanced Energy Facility, a proposed nuclear power plant near the Columbia Generating Station in Washington state [8]. The project, developed in partnership with Amazon, would house up to 12 Xe-100 small modular reactors and be operated by Energy Northwest, the operator of the only nuclear power station in the Pacific Northwest [8]. Participants include X-energy, Korea Hydro and Nuclear Power, and Doosan Enerbility [1]. As of 2026, X-energy was engaged in pre-application activities with the Nuclear Regulatory Commission but had not yet applied for a construction permit [8]. X-energy has received funding through the Department of Energy's Advanced Reactor Demonstration Program in 2020 and is developing a proprietary type of TRISO fuel called TRISO-X [6]. Fuel fabrication has progressed at Oak Ridge National Laboratory, where TRISO-X produces fuel at kilogram scale and is expanding commercial capacity [1]. Centrus Energy operates a U.S.-based HALEU cascade, and the Department of Energy has launched programs to accelerate commercial access [1]. "TRISO particle fuel is the most robust nuclear fuel we have ever developed," a nuclear-engineering professor and researcher focused on advanced reactor technologies said in the Amazon overview [1]. The resilience has been confirmed through the fabrication, irradiation, and testing of more than 500,000 TRISO particles since 2002 [1].