The diesel generator is a monument to compromise. It is loud, dirty, and expensive to run, but when the grid fails or never existed, it is the only thing that works. Radiant, a startup founded by former SpaceX engineers, thinks it has a better box. Its product, the Kaleidos microreactor, is a 1 MW nuclear power plant designed to fit inside a standard shipping container, be trucked or flown anywhere, and run for years without refueling [Radiant Nuclear, 2023].
Radiant has raised over $300 million from investors including Andreessen Horowitz, Founders Fund, DCVC, and Union Square Ventures [TechCrunch, Dec 2025]. The company is now valued at more than $1.8 billion [TechCrunch, Dec 2025].
The SpaceX playbook for nuclear
CEO Doug Bernauer spent 11 years at SpaceX, working on reusable rockets and the power systems needed for a future Mars base [Radiant Nuclear, 2023]. Bernauer and co-founder Bob Urberger started Radiant in 2019. Their approach borrows heavily from aerospace: design for manufacturability, prioritize safety through passive systems, and aim for a product that can be mass-produced [Radiant Nuclear, 2023]. The Kaleidos reactor is a high-temperature, gas-cooled design that uses TRISO fuel [Department of Energy, 2026].
To navigate the labyrinth of nuclear regulation, Radiant hired Dr. Rita Baranwal, the former U.S. Assistant Secretary for Nuclear Energy, in 2025 [LA Times, July 2025]. The company has submitted its first license application to the NRC and expects to begin fuel testing at Idaho National Laboratory by 2026 [ANS, 2026].
A market measured in diesel gallons
The target customer is anyone currently burning diesel for critical, off-grid power.
- The military. Radiant was selected by the U.S. Air Force for a potential deployment at Buckley Space Force Base [Eurasia Review, 2026].
- Data centers. The explosive growth of artificial intelligence has created a voracious, constant demand for power [Forbes, 2024].
- Disaster relief and remote industry. The ability to airlift a self-contained power source that runs for five years could rewrite the logistics of recovery [Forbes, 2023].
The capital and the clock
| Round | Date | Amount | Lead Investor(s) |
|---|---|---|---|
| Series A | 2022 | $11 Million | Union Square Ventures [Not Boring, 2023] |
| Series B | April 2023 | $45 Million | Andreessen Horowitz [Not Boring, 2023] |
| Series C | 2024-2025 | $165 Million | DCVC [PitchBook, May 2025] |
This capital is funding a long and expensive runway. The company has secured fuel supply agreements with Centrus Energy and Urenco [Radiant Nuclear, 2026] [Urenco, 2025]. The stated goal is to begin initial customer deployments in 2028 [LA Times, 2026].
Where the fission stops
- The regulatory gauntlet. The NRC's licensing process for a novel reactor design is measured in years.
- The manufacturing leap. Success requires the ability to produce reactors reliably, safely, and at a cost that makes the diesel replacement math work.
- Public perception. Radiant will need to educate customers, communities, and regulators.
The diesel displacement math
A large diesel generator set might burn about 70 gallons of fuel per hour at full load to produce 1 MW. Over a year of continuous operation, that's roughly 600,000 gallons of diesel. At $4 per gallon, that's $2.4 million in fuel cost alone. Radiant's reactor, once fueled, would theoretically have zero fuel cost for its multi-year cycle. The economic case hinges entirely on whether the upfront price of the reactor can undercut that massive, ongoing diesel bill over the system's 20-year lifespan [Interesting Engineering, 2026].