Deep Fission Drills a Test Well in Kansas for Its 15 MWe Deep Subsurface Pressurized Water Nuclear Reactor Design

   

     Company Deep Fission, founded by father and daughter Richard and Liz Muller, thinks they can design a way to produce nuclear power from deeply buried micro-reactors, and they think their method can reduce timelines for nuclear deployment. They are aiming for a deployment timeline of two to three years vs. ten years for conventional nuclear. One reason for this is that safety is more easily ensured underground. The method involves drilling a large-diameter hole, 50 cm (about 10 inches) in diameter, at depth for the reactor. Oil and gas companies typically drill holes this large and larger, but usually for closer-to-surface applications. A hole of this size is required to house the reactor-canister, which is expected to be lowered down into the hole. That is what the company did in a recent test well in Kansas, presumably drilled into Precambrian granite. They drilled the well about 1.8 km (about 5900ft) deep, lowered the canister in and retrieved it.

     Henk Kombrink of GeoExPro recently wrote about the project:

“The idea is for the small pressurised water reactor to be placed in a canister, lowered down the hole, which is subsequently filled with water. One reactor is supposed to generate around 15 MWe, which is not that much, and compares to what a prolific geothermal well can produce. But in this case, there is no scaling nor a temperature decline.”

     Below, he illustrates the company’s ambitious hopes for broad and fast deployment:

“The company has now started to drill the second well in their campaign, and also announced that they already have signed Letters of Intent with various data centres and other industrial entities for the delivery of a total of 18.5 Gw of generation capacity. That would require more than 1,000 wells, meaning that the technology needs to upscale fast. Since the company aims to use known technology, with the only difference being the new setting, the teething issues may hopefully be limited.”

     A Deep Fission press release from September 10, 2026, gives more detail into the recent test and design principles. The company’s CEO points out that all of the components and contractors for the system are commercially available, which should also accelerate deployment capability.

“On Thursday, September 3, 2026, the crew lowered the 20-foot canister to 100 feet depth inside a 34-inch-wide borehole, aligned it, and brought it back to the surface. This is the emplacement and retrieval sequence that Deep Fission's deployment model depends on. The equipment used is available today from commercial drilling contractors.”

     The 34-inch hole is likely a surface casing, where larger diameter holes are required. These are required to protect groundwater drinking sources.

"The most important thing about this demonstration is what we did not have to do," said Liz Muller, CEO and Co-Founder of Deep Fission. "We did not have to develop new technology. We used a rig and rigging that is commercially available in the field today, and our reactor uses pressurized water technology that has been operating in the nuclear industry for decades. Our innovation is in how we put proven pieces together, not in inventing something that has never been built. That is the difference between a science project and something you can deploy."

     The company can bank its 15MW micro-reactors by drilling additional wells for projects, where 10 wells = 150 MW and 100 wells = 1,500 MW. 

     The company also recently published its DOE-approved Nuclear Safety Design Agreement.

References:

 

Drilling a well to produce nuclear energy: How a US company brings together technology from the oil and gas and nuclear sectors to build small nuclear reactors one mile below the ground. Henk Kombrink. September 10, 2026. Drilling a well to produce nuclear energy - GeoExpro

Deep Fission. Website. Advanced nuclear energy deployment :: Deep Fission, Inc. (FISN)

Deep Fission Installs and Retrieves Full-Scale Reactor Canister Using Off-the-Shelf Drilling Equipment. Press Release. September 10, 2026. Deep Fission Installs and Retrieves Full-Scale Reactor Canister Using Off-the-Shelf Drilling Equipment :: Deep Fission, Inc. (FISN)

Deep Fission Publishes DOE-Approved Nuclear Safety Design Agreement for Gravity™ Pilot Reactor, Demonstrating Commitment to Transparency. Press Release. September 15, 2026. Deep Fission Publishes DOE-Approved Nuclear Safety Design Agreement for Gravity™ Pilot Reactor, Demonstrating Commitment to Transparency :: Deep Fission, Inc. (FISN)

Deep Fission Gravity Reactor Nuclear Safety Design Agreement (NSDA) Document ID: RPP-LIC-NSDA-NP Revision: 0. July 17, 2026. RPP-LIC-NSDA-NP+-+Rev+0.pdf