Pentagon Bets $2.2 Billion on Nuclear Microreactors for Army Bases

By Daniel Okafor

The U.S. Army has committed $2.2 billion to install nuclear microreactors at its biggest domestic bases by 2028, stepping in as private nuclear hype fades. Stock valuations are down. Planned IPOs are canceled. The federal government is now the anchor customer for the smallest class of reactors.

In June, startup Antares switched on its Mark-0 microreactor. It was the first to reach criticality in the Trump administration's pilot program race for next-generation reactors. Antares next plans to install its 1-megawatt R1 reactor at Fort Bragg, North Carolina, by September 2028. Founder and CEO Jordan Bramble wants an R1-S — the S stands for "space" — on the moon by 2030. In September, the Department of Defense awarded Antares $161 million to develop the R1-S integrated with spacecraft for flight certification.

"We'll need fission power on the dark side of the moon," Bramble told Fortune. "Fission is going to be our best path to doing very high-powered things in orbit. If we're going to send landers to Europa and Enceladus and Triton and try to find microbial life under the ice, we're probably going to need fission power to do that."

Why does the military want tiny reactors?

Project Janus, the Army's $2.2 billion program announced in August, funds reactors for Lower 48 bases. The goal is twofold: prove reliability and protect critical defense infrastructure from grid failures. The Army plans to fund 20 microreactors for domestic bases through the early 2030s, then let economies of scale make the technology commercially viable.

The biggest Janus recipient is Radiant, a startup building a transportable 1-megawatt reactor. That output powers roughly 750 homes. The unit fits in the space of "three parking spaces," the company says. Radiant's first projects sit at Fort Benning in Georgia and Buckley Space Force Base in Colorado.

COO and president Tori Shivanandan frames the demand in logistical terms. "The U.S. has struggled, and not just in major conflicts, in supporting troop deployments internationally," she told Fortune. "If you're moving your troops around and you want defense systems to protect those troops as they are deployed overseas, you also need to make sure that you have the power available to defend your troops."

This year's war in Iran exposed U.S. bases in the Middle East to drone attacks. Fuel convoys remain a repeatable target. "A diesel generator needs to be refueled every one to two days," Shivanandan said. "In previous conflicts in the Middle East, those were our largest targets for our adversaries because fuel convoys create repeatable paths. Our unit doesn't need to be refueled for three years."

What does the Army view say?

Jeff Waksman, the Army's top energy official, recites a military saying: "Amateurs talk tactics, professionals talk logistics." The nuclear physicist leads both Project Janus and the earlier Project Pele for a transportable reactor.

"As we look to the future of warfare, it is becoming increasingly electrical," Waksman told Fortune, citing drone warfare and more. "We have a lot of applications where being able to have a lot of power, not needing to refuel for a long period of time, and being able to do that in a fairly transportable way could be absolutely game changing."

Waksman draws a hard line on combat use. "We don't have any plans at this time to take these into conflict zones. We want to be clear about that." He cites possible future deployments to austere spots such as the Arctic or Pacific islands, but only after domestic proof. "It's one thing to turn a reactor on for five minutes at low power. It's another thing to turn a reactor to full power, which nobody has done with these microreactors."

The initial goal is not powering entire bases. It is keeping critical operations online during outages, in an age of AI and rising cybersecurity threats. The reactors would serve as permanent power, not backup generation. "If people can't get lunch, that's a problem, but that's not national security critical," Waksman said. "We're focused on what the critical operations are on those installations."

How do the competing designs differ?

General Atomics, a 71-year-old defense contractor, is building the GA-TES Tactical Energy System, a commercial version of its TRIGA research reactor first developed in the late 1950s. The reactor scales from 5 to 20 megawatts and is slated first for Fort Hood in Texas. It is air-cooled, so it needs no water source.

"It's good for places that are remote. It costs a lot of money to move the fuel up there. You don't want to have to keep carting up coal or natural gas or whatever," said Christina Back, GA's vice president for nuclear technologies and materials. She cited Guam and Alaska, and said the system needs refueling only every four to six years.

Back argued that demand will concentrate at the two ends of the market: large reactors such as Westinghouse's 1.1-gigawatt AP1000, and microreactors. Midsized small modular reactors may struggle to find buyers. She also dismissed 1-megawatt units as too small for Army needs, and called combat-zone deployment impractical given setup time. "As a company, we don't need to worry about the next Series A startup money, so we are very careful about what we say," Back said.

Radiant pushes back on buried designs. "Once you dig a hole in the ground and put a reactor in there, that is a nuclear site forever," Shivanandan said, referring to competitors that dig holes at least 50 feet deep. "You've limited the customer for those in-ground systems mostly to utilities."

The rivals agree on one thing: they welcome the administration's push to speed up permitting and the growing bipartisan support in Congress as memories of the 2011 Fukushima disaster fade. "We tend to be very conservative because the nuclear industry can't afford an accident," Back said. "We're taking a little bit longer than the 1-megawatt startups hurrying to show it works, because we're building something to last."

The technology still needs commercial proof outside testing labs. The Navy's nuclear submarines and carriers remain the only decades-long precedent. Whether Fort Bragg in 2028 becomes the first of many installations — or a one-off demonstration — will decide if microreactors graduate from Pentagon subsidy to standalone market.