Nuclear power is in a hole. To get out, this start-up kept digging

In the spring of 2024, a giant robot began attacking an underground nuclear reactor near Stockholm. The victim was the Ågesta Power Plant, Sweden’s first commercial pressurized water reactor, and the motive, as so often, was money. 

The reactor was built in 1963 to power Ågesta, a ritzy suburb of soaring trees and sparkling lakes. Its builders thought they were being smart by excavating an air-tight cavern half as tall as the Statue of Liberty, then squirreling away the reactor beneath 50 feet of solid bedrock.

Not only would the rock minimize the risk from accidents, they thought, it would also protect Ågesta from attack, a constant worry in the chill of the Cold War. 

But the real threat came from something far more mundane. Excavating, constructing and operating an underground reactor was ruinously expensive, and by the mid-1970s, economics forced Ågesta to close. 

Engineers in the US and elsewhere returned to the idea of underground nuclear power stations over the decades but there was always that nagging problem of expense. Digging a cavern large and deep enough to add real safety would blow gaping holes in already colossal budgets. 

Now one startup thinks it has cracked the problem. 

Deep Fission, based in Berkeley, California, offers the tantalizing promise of ultra-safe underground nuclear reactors that produce power as cheaply as solar farms. What’s more, its version of a nuclear renaissance uses the very tools developed to extract fossil fuels, to replace them instead.

The problem with earlier reactors like Ågesta, thinks Elizabeth Muller, Deep Fission’s CEO, is that they couldn’t dig anywhere near deep enough. And thanks to fracking, that’s all changed.

“We’re able to draw on work that’s been done by the oil and gas industry to drill holes a mile, two miles, four miles deep,” says Muller. “If you’re in a borehole mile underground, you have the exact conditions to create a pressurized water reactor without the construction costs, which are 80% of the cost of current nuclear plants.”

And because most of it is underground, this is a nuclear power plant that looks nothing like any nuclear power plant you’ve seen before.