X-energy Begins First Irradiation Tests of Advanced Nuclear Fuel Pebbles at Idaho National Laboratory

X-energy, LLC began testing at Idaho National Laboratory (INL) to evaluate the performance of their advanced nuclear fuel, TRISO-X.  

This is the first time that TRISO-X fuel pebbles will undergo irradiation testing in a U.S. lab, a critical step in meeting requirements set forth by the U.S. Nuclear Regulatory Commission for the commercial deployment of advanced reactors that will use the fuel. 

The test campaign is part of X-energy's larger efforts to establish the country’s first commercial advanced nuclear fuel fabrication facility to support the deployment of their small modular reactor design, the Xe-100, and other commercial reactors. 

TRISO-X Testing 

Irradiation testing of TRISO-X fuel will take place over the next 13 months at INL’s Advanced Test Reactor facility.  The experiments will evaluate how the fuel performs under various power levels, temperatures, and burnup conditions to simulate a wide range of operating scenarios. 

TRISO-X is a specialized version of TRISO fuel, a new class of advanced nuclear fuel favored by many advanced reactor developers. The fuel will be fabricated into billiard ball-sized spheres called “pebbles” that were developed by X-energy to power high temperature gas-cooled reactors, such as the company’s small modular reactor design, the Xe-100.   

TRISO fuel particles are made up of 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. 

Due to this novel structure, TRISO fuels cannot melt in a commercial high-temperature reactor and can withstand extreme radiation and temperatures that are 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 U.S. innovation in fuel design and this testing program brings us one step closer to redefining the standard for safety and reliability in nuclear energy." 

"The experiment cycle that started at INL's Advanced Test Reactor is a huge one for supporters of advanced nuclear," said Dan Wachs, the National Technical Director for DOE's Advanced Fuels Campaign. "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."

What’s Next? 

Once testing in the ATR is complete, post-irradiation examination will begin at INL and Oak Ridge National Laboratory as TRISO-X continues in its journey to qualify for commercial use. 

X-energy's TX-1 fuel fabrication facility is currently under construction in Oak Ridge, Tennessee, and could be the first advanced nuclear fuel fabrication facility licensed by the NRC in more than fifty 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 Inc. 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 the TX-1 commercial TRISO fuel fabrication facility. 

The first units of the Xe-100 will be built in Seadrift, Texas at Dow’s Seadrift manufacturing site and are anticipated to be the first grid-scale advanced nuclear reactors deployed to supply power and high-temperature heat to industrial-scale operations.