US-based X-energy Reactor Company has begun testing at Idaho National Laboratory (INL) to evaluate the performance of their TRISO-X advanced nuclear fuel. This is the first time that TRISO-X fuel pebbles have undergone irradiation testing in a US national lab. This is a critical step in meeting the requirements of the US Nuclear Regulatory Commission (NRC) for the commercial deployment of advanced reactors that will use the fuel.
The test campaign is part of X-energy’s overall plans to establish the first US commercial advanced nuclear fuel fabrication facility to support the deployment of their small modular reactor (SMR) design, the Xe-100, and other commercial reactors.
Irradiation testing of TRISO-X fuel will take place over the next 13 months at INL’s Advanced Test Reactor (ATR) facility. The experiments will evaluate how the fuel performs at various power levels, temperatures, and burnup conditions to simulate a wide range of operating scenarios.
TRISO-X is a specialised type of TRISO (tristructural-isotropic) fuel, which is favoured by many advanced reactor developers. The fuel will be fabricated into billiard ball-sized spheres or “pebbles” developed by X-energy to power high temperature gas-cooled reactors, such as the Xe-100. The first units of the Xe-100 will be built in Texas at Dow Company’s Seadrift manufacturing site.
TRISO fuel particles comprise a uranium, carbon and oxygen fuel kernel. The kernel is encapsulated by three layers of carbon- and ceramic-based materials that prevent the release of radioactive fission products. As a result, TRISO fuels cannot melt in a commercial high-temperature reactor and can withstand extreme radiation and temperatures well beyond the threshold of current nuclear fuels.
“What began in Oak Ridge as a pioneering effort to advance TRISO manufacturing is now leading the way in qualifying the fuel that will power the next generation of reactors,” said J Clay Sell, CEO of X-energy. “TRISO-X embodies decades of US innovation in fuel design and this testing programme brings us one step closer to redefining the standard for safety and reliability in nuclear energy.”
Dan Wachs, the National Technical Director for the Department of Energy’s (DOE’s) Advanced Fuels Campaign, said the experiment cycle that started at INL’s ATR is “a huge one for supporters of advanced nuclear”. He added: “The test marks INL’s first irradiations of TRISO fuel for advanced reactors since 2020 and the first use a new lead-out test capability at ATR that makes these advanced fuel tests possible.” Once testing in the ATR is complete, post-irradiation examination will begin at INL and Oak Ridge National Laboratory.
X-energy’s TX-1 fuel fabrication facility, currently under construction in Oak Ridge, Tennessee, could be the first advanced nuclear fuel fabrication facility licensed by NRC in more than 50 years. The facility will support the commercial deployment of the Xe-100 which is one of two advanced reactor demonstration projects supported through DOE’s Advanced Reactor Demonstration Program.
X-energy’s subsidiary TRISO-X is also participating in DOE’s new Fuel Line Pilot Program to build and operate an additional fuel fabrication laboratory facility to enable pilot-scale integration, training, and system validation to support TX-1. In August, X-energy and TRISO-X selected Clark Construction Group for the building construction phase of the TX-1 facility.
