A resident of Parsons, Kansas, the town Deep Fission has picked for its first reactor site, might reasonably worry about a nuclear plant showing up nearby: the containment dome, the security perimeter, the visible footprint. A drilling test in California this month points toward a design with almost none of that on the surface.
What Actually Happened in the Test
On September 3, a commercial drilling crew in California lowered a 20-foot steel canister into the ground, then pulled it back out. Nothing exploded. Nothing broke. For Deep Fission, the startup behind an underground reactor design meant to sit nearly a mile beneath the surface, that quiet result was exactly the point. The Deep Fission underground reactor design just cleared its first physical hurdle: proving that ordinary drilling equipment can handle a reactor-sized object without any custom engineering. According to the company, the answer is yes.
Deep Fission’s crew guided a full-scale, non-nuclear replica of its reactor canister into a 34-inch-wide borehole and set it at 100 feet, a fraction of the roughly one-mile depth the finished design calls for. The rig then hoisted the canister back to the surface intact. No custom-built tools handled the job. A standard commercial drilling and rigging crew ran the whole operation with gear they already owned, as World Nuclear News first reported.
Why Borrowing Old Technology Is the Real Advance
Plenty of advanced reactor companies have had to invent new manufacturing processes, new fuel forms, or new construction methods just to get their designs built. Deep Fission CEO Liz Muller framed her company’s approach as the opposite. “We did not have to develop new technology,” she said. “Our innovation is in how we put proven pieces together.” Other companies chasing faster, cheaper nuclear builds have gone the harder route of engineering new hardware from scratch, like the additive manufacturing behind 3D-printed nuclear pressure vessels. Deep Fission is betting that borrowing an entire existing industry, oil and gas drilling, beats inventing a new one from scratch.
The Gravity reactor itself is a pressurized water design running on standard low-enriched uranium, the same fuel type that has powered commercial reactors for decades. Deep Fission has already secured a Nuclear Safety Design Agreement from the Department of Energy and is advancing the project through the DOE’s Reactor Pilot Program, with its first planned site in Parsons, Kansas.
What a Mile of Rock Does for a Nearby Town
Here’s the bigger idea behind the drilling test. At full depth, Deep Fission’s design places the reactor inside a water-filled borehole surrounded by solid rock. That combination of rock and water handles containment, operating pressure, heat transfer, and emergency cooling all at once, jobs that conventional plants split across a domed containment building, pumps, and multiple layers of engineered barriers. Push those functions underground, and the reactor needs far less surface infrastructure: fewer buildings, fewer systems to maintain, fewer failure points exposed to the weather or to outside threats. For a town like Parsons, that means the physical presence of a “nuclear plant” could end up looking like little more than a fenced wellhead, not a cooling tower on the skyline.
What to Watch Next
Other developers are leaning on the same logic of testing hardware early instead of running paper studies alone. Kaleidos microreactor testing at Idaho National Laboratory follows a similar playbook: prove the physical build works before scaling it up. Deep Fission still has a long road ahead. Full system integration, regulatory sign-off, and eventually a real nuclear core instead of an empty replica all still lie in front of the company. But it just cleared a step that trips up plenty of nuclear projects: proving the physical deployment process actually works before spending years and billions finding out the hard way.