The global artificial-intelligence boom has spawned thousands of data centers in every corner of the planet. A technological leap forward, but an enormous challenge from an energy standpoint.

To power these data centers, which are getting larger and hungrier by the month, companies are on a constant hunt for electricity that is reliable, cheap, and able to run day and night, regardless of the weather.

A solution to the problem may have been found by the American startup Deep Fission, which proposes installing small nuclear reactors 1.6 kilometers (about one mile) underground.

Deep Fission’s radical idea

Deep Fission, founded in 2023 by Liz Muller and her father Richard Muller, a physicist emeritus at the University of California, Berkeley, is not scrambling, unlike many of its competitors, to develop brand-new reactor designs. The father-daughter team’s idea is to take conventional pressurized water reactors (PWRs) and drop them into shafts drilled 1.6 kilometers (about one mile) deep.

Shifting the reactor’s location, they argue, would move it out of the traditional above-ground nuclear plant and hand the containment job to the surrounding rock itself. And not only that: it would also cut construction costs and speed up how quickly the plants can be built.

It is a striking idea built on an extremely simple concept: bore a 76-centimeter (30-inch) hole into the ground, fill it with water, then lower in a mini nuclear reactor that heats the liquid and sends it up to a steam turbine through a separate pipe.

Each hole, according to the Mullers, would generate roughly 15 megawatts, about the electricity needed to power 12,000 homes. With 70 of them, it would be possible to keep a single data center running.

The system could also prove cheaper: estimates point to about 6 US cents (roughly 5 euro cents) per kilowatt-hour produced, and an 80% reduction in costs compared with a traditional concrete-and-steel plant.

A final selling point of Deep Fission’s system is the ease of fuel supply. Its creators say they can use standard low-enriched uranium without needing to modify the supply chain or build a new fuel from scratch.

The project still has to enter its crucial phase

Caution is essential when dealing with such delicate matters. Richard and Liz Muller announced the project in 2024, drawing on the experience they had built up with Deep Isolation, a company that develops technology for the underground storage of radioactive waste, and they have raised $4 million (about €3.5 million) in funding.

Now that innovative idea has to be carried into the real world. The company has recently confirmed that it has completed the design phase and wrapped up its first discussions with the US nuclear regulatory authorities.

Right now Deep Fission is working to set up its first pilot project at the Great Plains Industrial Park in Kansas, where engineers have already drilled a well 1.8 kilometers (about 6,000 feet) deep and are ready to collect the geological data needed to move to the next stage.

By the first half of 2027, official tests with reactor prototypes and applications for commercial licenses in the United States are expected to follow.

Editor’s note

This article was originally published in Italian on money.it by Andrea Fabbri on July 15, 2026 as «Pronti i reattori nucleari sotterranei per sostenere le richieste energetiche dei data center AI». It has been translated and adapted for an international audience by the Money.it International desk.