Radiant Nuclear Is Aiming to Build Microreactors ASAP

At one point during his 12-year stint at SpaceX, Doug Bernauer turned his attention to powering a Martian colony with nuclear microreactors. Naturally, these would also fuel the rocket ships that could shuttle Mars-dwellers to and from Earth as needed. Then he had an epiphany. “I quickly realized that yes, nuclear power could help humanity become multiplanetary in the long term, but it could also transform life on Earth right now,” Bernauer wrote in 2023.

Indeed it can.

As nuclear power reemerges as a prominent player in the U.S. energy conversation, its potential to help drive a decarbonized future has crystallized into a rare bipartisan point of consensus. Radiant Nuclear, the Earth-based microreactor company that Bernauer founded after leaving SpaceX in 2019, is well positioned to take advantage of that, as its value proposition might as well be tailor-made for the Trump administration’s priorities

The startup’s aim is to make highly portable 1-megawatt reactors that can replace off-grid power sources such as diesel generators, which are ubiquitous in remote areas such as military bases. It’s fresh off a $165 million Series C funding round, with plans to begin commercial deployment in 2028. That aligns neatly with Trump’s recently announced goal of deploying a reactor on a military base by the same year. It’s an opportunity that Radiant Chief Operating Officer Tori Shivanandan told me the company is uniquely well-suited to take advantage of.

“A diesel generator that operates at 1 megawatt you have to refill with diesel about every three to five days,” Shivanandan explained. That means having regular access to both fuel and the generator itself, “and that’s just not reliable in many locations.” The company says its reactors only need refueling only every five years.

Radiant’s goal is to be cost competitive with generators in far flung locales — not just military bases, but also distant mines, rural towns, oil and gas drilling operations, and smaller, more dispersed data centers. “A customer who’s on the North Slope of Alaska, they might pay $11 or $12 a gallon for diesel,” Shivanandan told me. That’s a price she said Radiant could definitely compete with.

“The military’s interest in microreactors has been coming for quite a long time,” Rachel Slaybaugh, a climate tech investor at the venture firm DCVC told me. The firm led Radiant’s Series C round. Some of Radiant’s appeal is “right place, right time,” she said. “Some of it is putting in a lot of work over a long time to make it the right place, right time.”

Trump’s recent nuclear-related executive orders also have Shivanandan and her team over the moon. As the administration looks to streamline nuclear licensing and buildouts, one order explicitly calls for establishing a process for the “high-volume licensing of microreactors and modular reactors,” which includes “standardized applications and approvals.” These orders, Shivanandan told me, will keep Radiant on track to start selling by 2028, and set the stage for the company’s rapid scale up.

Alongside DCVC, the company's latest round included funding from Andreessen Horowitz’s “American Dynamism” team, Union Square Ventures, and Founders Fund. This raise, Shivanandan told me, will cover Radiant’s expenses as it builds out its prototype reactor, which it plans to test at Idaho National Lab next year. It will be the first fueled operation of a brand new reactor design in 50 years, she said.

“My perspective is the bigger reactors are important and interesting, and there are a lot of great companies, but they’re not a very good fit for venture investing, Slaybaugh told me. “We like microreactors, because they just need so much less capital and so much less time.”

That potential buildout speed also means that even as the Inflation Reduction Act’s clean energy tax credits look poised for a major haircut, Radiant may still be able to benefit from them. In the latest version of the budget bill, nuclear projects are only eligible for credits if they begin construction by 2029 — a tall order for the many startups that likely won’t start building in earnest until the 2030s. But if all goes according to plan, that’s a timeline Radiant could work with — at least for its initial reactors, which would be the most expensive and thus most in need of credits anyway.

The company aims to reach economies of scale relatively quickly, with a goal of building 50 reactors per year at a yet-to-be-constructed factory by the mid 2030s. The modular design means Radiant can deploy multiple 1-megawatt reactors to facilities with greater power needs. But if a customer wants more than 10 or so megawatts, Radiant recommends they look to microreactors’ larger cousins, the so-called small modular reactors. Companies developing these include Last Energy, which makes 20-megawatt reactors, as well as NuScale, Kairos, and X-energy, which aim to build plants ranging from 150 megawatts to 960 megawatts in size.

While it could take one of these SMR companies years to fully install its reactors, Radiant’s shipping container-sized products are not designed to be permanent pieces of infrastructure. After being trucked onsite, the company says its reactors can be switched on the following day. Then, after about 20 years of continuous operation, they’ll be carried away and the site easily returned to greenfield, since there was no foundation dug or concrete poured to begin with.

This April, the Department of Defense selected Radiant as one of eight eligible companies for the Advanced Nuclear Power for Installations Program. The winner(s) will design and build microreactors on select military installations to “provide mission readiness through energy resilience” and produce “enough electrical power to meet 100 percent of all critical loads,” according to the Defense Innovation Unit’s website.

Also on this list was the nuclear company Oklo, which counts OpenAI CEO Sam Altman among its primary backers and went public last year. This Wednesday, the Air Force announced its intent to enter into a power purchase agreement with the company to build a pilot reactor on a base in Alaska. The reactor will reportedly produce up to 5 megawatts of power, though Oklo’s full-scale reactors are set to be 75 megawatts. Whether the military will opt to contract with other nuclear companies is still an open question.

Perhaps more meaningful, though, is the show of support Radiant recently gained from the Department of Energy, which selected it as one of five companies to receive a conditional commitment for a type of highly enriched uranium known as HALEU that’s critical for small, next-generation reactors. Much of this fuel came from Russia before Biden banned Russian uranium imports last year, in a belated response to the country’s invasion of Ukraine and an attempt to shore up the domestic nuclear supply chain.

America’s supply of HALEU is still scarce, though, and as such, Shivanandan considers the DOE’s fuel commitment to be the biggest vote of confidence Radiant has received from the government so far. The other companies selected to receive fuel are TRISO-X (a subsidiary of X-energy), Kairos Power, TerraPower, and Westinghouse, all of which have been around longer — the majority a decade or more longer — than Radiant.

Though the company is currently focused on Earth, Radiant hasn’t completely abandoned its interplanetary dreams. “We do believe that, should you want to colonize Mars and also create the environment in which you could refuel your rocket and send it back, then you would need 1-megawatt nuclear reactors,” Shivanandan told me. Anything larger might be too heavy to put in a rocket.

Good to know.