Deep Fission teams with Youngquist on deep borehole drilling for underground reactors

Deep Fission announced a collaboration with Youngquist Brothers to evaluate and test drilling and borehole-construction methods for placing small modular reactors in deep boreholes. The companies also described a September 3 demonstration in Fort Myers that lowered and retrieved a 30-inch prototype canister in a 34-inch borehole to about 100 feet.

Deep Fission is pairing its underground reactor concept with a commercial large-diameter drilling specialist, disclosing the collaboration in a Form 8-K furnished under Regulation FD.

The collaboration

On September 21, 2026, Deep Fission, Inc. (Nasdaq: FISN) said it will work with Youngquist Brothers, LLC to evaluate and test drilling technologies and borehole-construction methods for the company’s underground reactor deployment model. Deep Fission describes itself as an advanced nuclear company working to place small modular pressurized water reactors in boreholes about one mile underground. Youngquist is characterized in the release as a commercial drilling contractor that specializes in large-diameter boreholes.

Under the collaboration, the companies plan to advance and test methods for constructing large-diameter, deep boreholes, drawing on Youngquist’s drilling and borehole-construction experience. The Form 8-K furnishes the announcement as Exhibit 99.1 and states that the Item 7.01 information is not deemed “filed” for Exchange Act Section 18 purposes except where specifically incorporated.

Fort Myers demonstration

Separately from the full-depth drilling work the collaboration is meant to cover, the companies said that on September 3, 2026, in Fort Myers, Florida, they completed a related equipment demonstration. Deep Fission lowered and retrieved its 30-inch full-size prototype reactor canister into a 34-inch borehole to a depth of approximately 100 feet using Youngquist’s proprietary drilling technologies and equipment. The release says that demonstration focused on installation and retrieval mechanics.

Youngquist’s CEO, Harvey Youngquist, is quoted saying the firm has refined large-diameter drilling to these depths since 1971, and Deep Fission CEO and co-founder Liz Muller said working with an established commercial driller lets the company advance the drilling side of its approach with equipment and expertise that already exist in the field.

Deployment context

Deep Fission’s Gravity Nuclear Reactor approach, as described in the release, uses established pressurized water reactor technology and standard low-enriched uranium fuel and is designed to secure the reactor roughly a mile underground in a water-filled borehole, with surrounding rock and water intended to support containment and cooling. The company said it intends to continue borehole drilling and testing with Youngquist as it advances toward commercial deployment, which it is targeting as early as 2027. The release also states Deep Fission is advancing its first reactor project in Parsons, Kansas, and was selected for the U.S. Department of Energy’s Reactor Pilot Program.

The disclosure does not provide contract value, exclusivity, capital commitments, or a binding schedule beyond the evaluate-and-test collaboration described in Exhibit 99.1.