3 Nuclear Startups Hit a Big Milestone. Why It Matters—and Why It Doesn’t

Three startups are providing the fireworks for the Department of Energy's Fourth of July celebrations by meeting a major nuclear milestone. They've turned on new reactors as part of a pilot program aimed at kick-starting what Energy Secretary Chris Wright calls “America’s nuclear renaissance” to develop and deploy the next generation of atomic energy.

Other companies in the pilot program have signaled that they may reach criticality—a term used to describe a nuclear reactor sustaining a chain reaction, a key step in providing power—shortly after July 4, following a deadline set by President Donald Trump in an executive order last year. But experts say that while the pilot is good PR for the industry, there’s still a long way to go before new reactor designs become commercial realities.

“These prototypes mean everything and nothing,” says Adam Stein, the director of the Nuclear Energy Innovation program at the Breakthrough Institute. “They do a lot for the companies reaching criticality, but even for those companies, they’re not commercial products. They’re test reactors.”

For decades, the American nuclear landscape has been dominated by large, light-water reactors, which use water to move heat and sustain the nuclear reaction. The dream of building smaller reactors with different, more innovative designs has long remained out of reach, thanks in part to a slow regulatory environment and the massive upfront cost required for small companies to develop new reactor designs.

“The industry has long been viewed as stuck—a nuclear reactor was always 10 years away,” says Stein. The pilot program “shows that’s not true, if you intentionally move faster. It changes the narrative, and it changes the perception. That means a lot for the investment community.”

A growing number of investors and tech figures in Silicon Valley see smaller nuclear reactors, which can provide 24/7 carbon-free energy to power data centers and other operations, as part of a new golden age of technology. The tech world has leaned heavily on the Trump administration to slash regulations and speed up the development of smaller nuclear designs. The administration has responded with a series of actions, including creating the pilot program via an executive order last year. In classic Trumpian fashion, the executive order, issued in May 2025, set an aggressive timeline to get at least three reactors critical, coinciding with the country’s 250th anniversary celebrations on July 4.

In February, the Department of Energy quietly slashed a number of environmental and safety regulations for reactors operating under that department’s purview, including the ones being built as part of the pilot program. (Similar regulatory cuts are now being worked out in the Nuclear Regulatory Commission, which approves reactors that will be sold commercially.) Stein says that shortening processes for requirements like environmental impact statements, which can take years, created “significant time savings” for companies in the program.

The reactor designs in the pilot program have benefited not just from cutting red tape. Several of the companies also have help from federally funded national laboratories. Valar Atomics reached criticality late last year onsite at Los Alamos National Laboratory using a core with the startup’s fuel and key structural components provided by the lab. (The company reached criticality again with a second reactor at a state-funded lab site in Utah earlier this month.) Antares Nuclear and Deployable Energy—the other startups in the pilot program that have met the executive order’s July 4 deadline—also reached criticality at national labs.

Matt Loszak, the cofounder and chief executive officer of Aalo Atomics, credits the government prioritizing new reactor development for the speed at which his company has been able to move. His company is part of the pilot program and has yet to hit criticality, though it expects to do so soon.

“Before, you’d try to get a signature, and maybe it would sit on someone’s desk for five weeks,” he says. “Now, it’s like, done the next day, because it’s a priority for the nation.”

Reaching criticality does not mean these reactors are necessarily generating electricity: Aalo’s reactor, for instance, is lacking the sodium component that the company’s final commercial reactor will have. (On Thursday, Valar’s reactor design powered an Nvidia chip during a short demonstration, becoming the first advanced reactor in the US to provide electricity.) And simply proving that criticality can happen in a lab setting—something that numerous college campuses do across the country—does not mean that a small reactor is ready to be hooked up to the grid or deployed to power a data center.

Commercial products will still have to go through licensing with the Nuclear Regulatory Commission, a process that has traditionally taken years. (Regulatory cuts from the Trump administration could significantly shorten the process; Wright told CNBC that the NRC is working with his agency to create a “fast” timeline for commercialization for the reactors in the program.) Stein says that supply chains, especially for fuel, could also pose a massive hurdle for companies in the pilot program looking to take their products to market. That’s particularly true for some of the companies that have had help from the Department of Energy sourcing fuel.

“It’s an amazing achievement to bring new reactors critical and deploy new reactor technology in 2026,” says Brett Rampal, the senior director of nuclear and power strategy at Veriten, an investing and strategy firm. (Aalo is a Veriten client.) But Rampal cautions that some in the industry may be over-romanticizing the idea of a new golden age for nuclear energy without fully acknowledging the financial realities that plants remain expensive and time-consuming to build.

“If you go back and you look at all the nuclear power plants we built throughout the country, on average, they were over cost and over budget,” he says.