Radiant closes $165 Million Series C with additional funding from Giant Ventures, StepStone, ARK Venture Fund, and others

Total funding reaches $225 million ahead of next year’s historic reactor test

May 28, 2025

May 28, 2025 — Radiant, the pioneer in mass-produced portable nuclear microreactors, announced today the successful close of its $165 million Series C funding round, bringing the company’s total venture funding to $225 million.

The latest round, led by DCVC, now includes new investments from StepStone, Giant Ventures, Hanwha Asset Management Venture Fund, SGA, Crossbeam Venture Partners, Align Ventures, ARK Venture Fund, Gigascale Capital, HartBeat Ventures, and Pax Ventures joining a growing roster of world-class investors backing Radiant’s mission.

The funding announcement follows the news that the U.S. Department of Energy has selected Radiant as one of just five companies in the United States to receive high-assay low-enriched uranium (HALEU) fuel. Radiant will be using this fuel for the first test of Kaleidos, the world’s first mass-produced reactor. This test is currently targeted for 2026 at the Idaho National Laboratory DOME facility.

Radiant’s Kaleidos 1MW microreactor is designed to replace diesel generators and can be rapidly deployed to provide resilient power for remote villages, emergency response, and military installations.

“Adding some of the smartest minds in technology investment to our team is a powerful vote of confidence in Radiant – and the belief that America must continue to lead the way in nuclear innovation – as we ramp up to test the first new reactor design in the U.S. in over 50 years,” said Doug Bernauer, CEO and Founder of Radiant.

"We are seeing a new nuclear renaissance play out right now," said Will Dufton, who leads Growth investments at Giant Ventures, "Radiant's success will uncork the final bottlenecks to progress for the entire nuclear industry."

Current investors in Radiant include Andreessen Horowitz’s American Dynamism team, who led Radiant’s Series B funding, Union Square Ventures, Founders Fund, Draper Associates, Felicis, Washington Harbour Partners LP, Chevron Technology Ventures, Decisive Point, McKinley Alaska, Nucleation Capital, Boost VC, Also Capital, and others.

The funding will primarily be used to complete Radiant’s Kaleidos Development Unit, and for factory siting and early construction efforts on the facilities that are expected to produce up to 50 microreactors per year.

For more information about Radiant and Kaleidos, visit www.radiantnuclear.com.

About Giant Ventures

Giant Ventures backs purpose-driven founders solving the world’s biggest challenges: from climate, to health, to economic mobility. Led by former founders, Giant invests in companies in Europe and the US.