New Space and Tech

TRISO-X Successfully Completes Fuel Test to Power Nuclear Thermal Propulsion in Space

By Keith Cowing
Press Release
X energy
March 16, 2023
Filed under , , , , ,
TRISO-X Successfully Completes Fuel Test to Power Nuclear Thermal Propulsion in Space
X energy
X energy

TRISO-X LLC (“TRISO-X”), a wholly owned subsidiary of X-Energy Reactor Company, LLC (“X-energy”) that primarily develops and designs tri-structural isotropic (“TRISO”) particle fuel, today announced the successful test of its coated particle fuel for nuclear thermal propulsion applications, marking a major step toward a one-of-a-kind, nuclear-powered rocket.

TRISO-X was tapped to develop key fuel fabrication processes as part of a team led by General Atomics Electromagnetic Systems (GA-EMS) for the first phase of the Defense Advanced Research Projects Agency’s (DARPA) Demonstration Rocket for Agile Cislunar Operations (DRACO) program, which concludes this month.

The U.S. Department of Energy (“DOE”) considers TRISO particle fuel “the most robust nuclear fuel on the planet.”

“We are thrilled to meet this crucial milestone that will help to enable the prospective deployment of a nuclear-thermal-propulsion-based rocket,” said Dr. Pete Pappano, President of TRISO-X. “The high-temperature resilience of our coated particle fuel bolsters TRISO-X’s position as the domestic leader in the fabrication, testing and commercialization of coated-particle fuel systems for both power and space applications. This is a key demonstration of the robust properties and performance of our coated particle fuel, demonstrating the fuel’s design to be melt-down proof under any foreseeable scenario.”

With the participation of NASA, the successful test took place at the Marshall Space Flight Center in the Compact Fuel Element Environmental Test (CFEET) facility. The TRISO-X fabricated fuel was tested in extreme conditions representing those experienced in space. The test was the first time TRISO-X’S—or, to TRISO-X’s knowledge, any— coated particle fuel was tested to these conditions. The fuel was cycled rapidly and repeatedly to more than 2,000 degrees Celsius with the temperature fluctuating hundreds of degrees per minute and held at those temperatures to replicate conditions anticipated during space missions, while maintaining its integrity.

TRISO-X occupies a laboratory located on the Oak Ridge National Laboratory campus in Oak Ridge, Tennessee, where it has leased research and laboratory space since 2016. TRISO-X broke ground last year in Oak Ridge on its commercial-sale Fuel Fabrication Facility (“TF3”), which is expected to be fully operational in 2025. The U.S. Nuclear Regulatory Commission formally docketed the facility license application in 2022 and its licensing review is ongoing.

The DOE selected X-energy in 2020 for their Advanced Reactor Demonstration Program (“ARDP”) to receive up to $1.2 billion of federal cost-shared funding to develop, license, build, and demonstrate operational advanced reactors and advanced nuclear fuel fabrication by the end of the decade. The TRISO-X nuclear fuel produced in the Oak Ridge TF3 will be used in X-energy’s Xe-100 high-temperature gas reactors..

As previously announced on December 6, 2022, X-energy entered into a definitive business combination agreement with Ares Acquisition Corporation (NYSE: AAC) (“AAC”), a publicly-traded special purpose acquisition company. Upon the closing of the transaction, which is expected to be completed in the second quarter of 2023, the combined company will be named X-Energy, Inc. and its common equity securities and warrants are expected to be listed on the New York Stock Exchange.

Completion of the transaction is subject to approval by AAC’s shareholders, the Registration Statement being declared effective by the SEC, and other customary closing conditions.

About X-Energy Reactor Company, LLC

X-Energy Reactor Company, LLC, is a leading developer of advanced small modular nuclear reactors and fuel technology for clean energy generation that is redefining the nuclear energy industry through its development of safer and more efficient advanced small modular nuclear reactors and proprietary fuel to deliver reliable, zero-carbon and affordable energy to people around the world. X-energy’s simplified, modular, and intrinsically safe SMR design expands applications and markets for deployment of nuclear technology and drives enhanced safety, lower cost and faster construction timelines when compared with other SMRs and conventional nuclear. For more information, visit or connect with us on Twitter or LinkedIn.

About Ares Acquisition Corporation

AAC is a special purpose acquisition company (SPAC) affiliated with Ares Management Corporation, formed for the purpose of effecting a merger, share exchange, asset acquisition, share purchase, reorganization or similar business combination. AAC is seeking to pursue an initial business combination target in any industry or sector in North America, Europe or Asia. For more information about AAC, please visit

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