Liz Muller convinced her dad Richard to forego retirement and become an entrepreneur. The result is a revolutionary approach to making atomic energy cheaper and safer.

For more than a decade, Elizabeth Muller and her father have taken a three-mile hike, usually twice a week, through the hills of Berkeley, California, stopping for coffee and brainstorming on the way. “I would have an idea and she would have an idea,” says Richard A. Muller, who devised the modern carbon dating method used to determine the age of ancient plant and animal remains before he was 33 and won a MacArthur Foundation “genius” award at 38. Now, after 40 years of teaching at the University of California at Berkeley, the 82-year-old physicist is on the verge of having his greatest commercial impact, thanks to his business-minded daughter and those long walks.

“Nuclear brings out big emotions on all sides,” says Liz, 47. “As a kid growing up in Berkeley, all my teachers and friends were anti-nuclear, and the city became a nuclear-free zone.” She too leaned anti-nuke, even though her father’s mentor, Nobel Prize winner Luis Alvarez—who worked with Robert Oppenheimer on the first atomic bomb—was “like a grandfather to me.” But after college at UC San Diego, she moved to Paris in 1999 to earn a master’s at ESCP Business School and worked in international finance there for eight years. In France, she explains, everyone supported nuclear power as a “clean, reliable global warming solution.” She returned to Berkeley determined to tap her dad’s genius. 

In 2022, on one of those walks, the Mullers hatched the idea behind their nuclear power startup, Deep Fission. The concept is surprisingly simple: Drill a 30-inch-diameter borehole a mile into the earth, fill it with water, then insert a teeny-tiny nuclear reactor that will boil the water at the bottom and send it up a separate pipe to run a steam turbine. Each hole will generate 15 megawatts, enough to power 12,000 homes. Put 70 of them in a field and you can power a one-gigawatt artificial intelligence data center. 

Once up and running, it should also be cheap (about six cents a kilowatt hour, they estimate), because sticking a reactor deep in the ground under 160 times atmospheric pressure eliminates 80% of traditional power plant costs, which go to concrete buildings and thick steel vessels. “We are using the gravity of the water to give the reactor the same pressure,” Richard explains. 

Last August the Department of Energy inclu­ded Deep Fission as one of ten companies in its Reactor Pilot Program, designed to quickly test a new generation of smaller reactors that are easier to build. “The pull of electric demand from data centers warranted a new approach,” says Rian Bahran, deputy assistant secretary for nuclear at the DOE. While the other reactors are innovative in their own ways, they’re all variations of the traditional above-ground model.

https://www.forbes.com/sites/christopherhelman/2026/04/02/acclaimed-physicist-and-his-daughter-are-burying-tiny-nuclear-reactors-a-mile-underground/

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