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Stack Capital Group Invests $5M in X-energy Nuclear Tech
The investment holding company backs the advanced nuclear reactor developer's growth.
Jan. 28, 2026 at 7:55am
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Stack Capital Group Inc., an investment holding company, has invested $5 million USD into X-energy Reactor Company, LLC, an advanced nuclear technology firm developing next-generation small modular reactors and proprietary nuclear fuel solutions. X-energy, founded in 2009 and based in Rockville, Maryland, is a leader in the commercialization of advanced nuclear power and has secured significant funding from both private investors and the U.S. Department of Energy.
Why it matters
The investment highlights the growing importance of advanced nuclear energy as a reliable, carbon-free power source to support the digital economy and long-term climate goals. X-energy's innovative reactor and fuel technologies position the company as a key player in the global shift towards sustainable energy infrastructure.
The details
Stack Capital, an investment holding company, has invested $5 million USD into X-energy, a Maryland-based advanced nuclear technology firm. X-energy specializes in developing next-generation small modular reactors, such as the Xe-100 and XENITH, as well as its proprietary TRISO-X nuclear fuel. The company has secured approximately $1.8 billion in private capital and up to $1.2 billion in funding from the U.S. Department of Energy's Advanced Reactor Demonstration Program. X-energy's technology and commercial partnerships with companies like Amazon, Dow, and Ontario Power Generation have positioned it as a leader in the global deployment of advanced nuclear power.
- X-energy was founded in 2009 and is headquartered in Rockville, Maryland.
- The investment by Stack Capital was announced on January 28, 2026.
The players
Stack Capital Group Inc.
An investment holding company that invests in equity, debt and/or other securities of leading growth-to-late-stage private businesses.
X-energy Reactor Company, LLC
An advanced nuclear technology company developing next-generation small modular reactors and proprietary nuclear fuel solutions, founded in 2009 and headquartered in Rockville, Maryland.
Jimmy Vaiopoulos
The CFO of Stack Capital Group.
What they’re saying
“Reliable, carbon-free baseload power is becoming one of the most critical constraints on global economic growth, particularly as AI, electrification, and industrial decarbonization accelerate.”
— Jimmy Vaiopoulos, CFO of Stack Capital Group (businessinsider.com)
“Advanced nuclear energy is uniquely positioned to meet this demand at scale, and X-Energy stands out as a category leader with differentiated technology, integrated fuel supply, and real commercial traction.”
— Jimmy Vaiopoulos, CFO of Stack Capital Group (businessinsider.com)
The takeaway
This investment highlights the growing importance of advanced nuclear technology as a key component of the global shift towards sustainable energy infrastructure. X-energy's innovative reactor and fuel solutions position the company as a leader in the commercialization of next-generation nuclear power, which will be crucial in supporting the digital economy and long-term climate objectives.
