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Deep Fission, a company that plans to install small nuclear reactors a mile underground, has raised $4 million for its technology.

Why it matters: The startup says its technology addresses two of the biggest costs holding back nuclear energy development.

The big picture: Nuclear reactors are the single biggest source of zero-emissions electricity in the U.S. They're also the most expensive to build.

More than a dozen startups are pursuing small reactor designs. But even those require costly pressure and containment systems or expensive advanced fuel.

Driving the news: Deep Fission says it's designed a tiny reactor that obviates the need for pressure or containment systems or special fuel. 

It closed a pre-seed round this summer, led by venture firm 8VC.

How it works: Deep Fission this year submitted a conceptual design overview for a 15 MW microreactor to the Nuclear Regulatory Commission.

The company would build the reactor above ground, then lower it down a 30-inch borehole a mile deep.

Zoom in: At that depth, there's enough natural pressure to spark and sustain a nuclear reaction. The bedrock meanwhile provides ample containment for safety, enabling the reactor to use lower-cost conventional fuel.

What they're saying: "If you look at your typical nuclear plant, 70-80% of the cost is in the physical materials: the steel, the cement," says CEO Elizabeth Muller.

"We're taking the construction cost out of nuclear power, without the need for advanced materials let alone advanced fuel."

The intrigue: The company's first reactor can turn a profit at current electricity prices, which in most markets are between 8-10 cents per kilowatt-hour, Muller says.

Context: Muller founded the company with her father, Richard Muller, a physics professor at the University of California, Berkeley, who's won the MacArthur Prize "genius award" and the Breakthrough Prize.

The Mullers previously launched Deep Isolation, a startup aiming to dispose of nuclear waste underground. It was Richard who thought up the idea of sparking a nuclear reaction.

"We started asking, 'Could we make it go critical? Can create an underground nuclear reactor?'" Muller recalls. 

What's next: Deep Fission is planning to launch a seed raise this fall.

The Berkeley, California-based company expects to submit a licensing application to the Nuclear Regulatory Commission in 2026 and aims to begin construction in 2028.

"We can probably get a reactor online in early 2029," Muller says.

Exclusive: $4 million for Deep Fission’s underground nuclear reactors

The startup is developing a 15 MW microreactor.

Photo illustration of a collage of a handshake, power plants and coal.

Photo illustration: Shoshana Gordon/Axios. Photo: Horst Galuschka/picture alliance via Getty Images

Nuclear power

Deep Fission, a company that plans to install small nuclear reactors a mile underground, has raised $4 million for its technology.Why it matters: The startup says its technology addresses two of the biggest costs holding back nuclear energy development.

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Exclusive: $4 million for Deep Fission’s underground nuclear reactors

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