The SpaceX engineer who built a nuclear reactor in a box
he first thing you notice when you cross the threshold of Radiant’s El Segundo HQ is how clean the factory is. You could practically eat your dinner off the floor, surrounded by the constituent parts of a nuclear reactor and some of the world’s most brilliant energy, machining and aerospace engineers. Not only does the facility sparkle, but everything, from parts to people, is in the right place. You get the sense that this is a tight ship that goes fast.
And you would be right. Radiant is building the Kaleidos, Earth's first mass-produced nuclear reactor, a 1MWe system that fits on the back of a truck or cargo jet. As of Q1 2026, they are assembling this reactor ahead of its fully fuelled test in July, the first full-scale demo of a new reactor design in the USA for 50 years. When Doug Bernauer started Radiant in 2020, he predicted this test would happen at the end of Q2 2026. He was out by just a few days.
“Will’s deep research and clear passion for the nuclear industry came through from the moment we met. I was impressed with how quickly he understood what we were building, why it mattered, and how fast Giant could move. Since that first meeting, they've been constant champions of our mission to mass produce portable nuclear reactors as we enter an era where we’re splitting Atoms for Prosperity.”
Doug has a track record of pulling the future forward. He joined SpaceX in 2008, and during an 11-year tenure he was trusted to engineer everything from the first rocket with legs to Hyperloop. Doug founded Radiant to meet America’s energy needs at home, in the most remote places on earth, and in space, by applying his learnings from SpaceX to nuclear.
Radiant is on track to spearhead a new renaissance for nuclear energy. Over the course of our partnership, they have already achieved some groundbreaking milestones - with strong regulatory progress with both the Nuclear Regulatory Commission and the Department of Energy, and key hires including Dr. Rita Baranwal, the former Assistant Secretary for Nuclear Energy as Chief Nuclear Officer, and almost a dozen VP and Director hires across engineering, manufacturing, and supply chain organizations.
Radiant milestones
Valuation following recent $300M+ Series C. Our co-investors include A16Z, Founders Fund, Boost and DCVC
America's first fueled test of a new nuclear design in 50 years
Sold 20 reactors to hyperscaler, Equinix
First company to sign a contract with the US government for High-Assay Low-Enriched Uranium (HALEU) fuel and first binding contract for enrichment services
It has been a pleasure seeing Doug and the incredible Radiant team consistently outperform. When a team executes like this, the best thing an investor can do is stay out of their way! Where Giant has worked closely with Radiant is in amplifying their story globally and leveraging our unique partnership with the world's leading consulting firm to build a bespoke go-to-market strategy.
Radiant is writing the next chapter for nuclear power and orchestrating a better, energy-abundant future for civilization.
Every Kaleidos reactor has a major impact on carbon emissions over its 20-year life.
