Department of Energy Approves Nuclear Safety Design Agreement for Deep Fission's Gravity™ Reactor, Designed to Convert to Commercial Operation

BERKELEY, Calif.--(BUSINESS WIRE)--Deep Fission, Inc. (Nasdaq: FISN) (“Deep Fission” or the “Company”), an advanced nuclear energy company developing small modular pressurized water reactors installed one mile underground, today announced that the U.S. Department of Energy (DOE), has approved the company's Nuclear Safety Design Agreement (NSDA) for its Gravity™ Nuclear Reactor. This marks a major regulatory milestone, confirming that Deep Fission's reactor design warrants advancement under the Department of Energy’s Reactor Pilot Program.

The NSDA approval establishes the safety framework that will guide the reactor's continued development. With this milestone in place, Deep Fission moves forward to the next phase of the DOE authorization pathway, advancing toward demonstration and eventual deployment of its underground nuclear reactor technology.

“This approval is a major step forward for Deep Fission,” said Liz Muller, co-founder and CEO of Deep Fission. “We believe our mile-deep design gives us the ability to move faster in the stages ahead.”

This regulatory progress comes as Deep Fission continues to advance its commercial pilot project at the Great Plains Industrial Park in Parsons, Kansas. Since breaking ground in December 2025, the company has drilled its first data acquisition well to 6,000 feet and recently delivered a prototype reactor canister to the site. Deep Fission is now progressing its proof-of-concept program, which includes large-diameter well drilling and prototype installation milestones, preceding full-scale demonstration at the site.

Deep Fission's Parsons project is not designed as a one-time criticality test. Consistent with the intent of Executive Order 14301 and the Reactor Pilot Program, the Company intends for its demonstration reactor to become a fully Nuclear Regulatory Commission-licensed, commercially operating unit, delivering power after initial testing and receiving DOE authorization. This reflects the Company's commitment to building a direct, credible path from demonstration to commercial deployment.

Deep Fission will continue working closely with the DOE as its design progresses through subsequent stages of review and authorization under the Reactor Pilot Program.

About Deep Fission

Deep Fission is developing technology that places a small modular pressurized water reactor in a borehole approximately one mile underground. The Company’s Gravity Nuclear Reactor™ approach combines established pressurized water reactor technology with a novel underground deployment model designed to simplify construction, enhance safety, and support scalable commercial deployment. Deep Fission is focused on delivering reliable, low-carbon baseload power to meet growing electricity demand from utilities, industrial customers, and data centers. The Company is currently advancing the development of its first reactor project in Parsons, Kansas and was selected for the U.S. Department of Energy’s Reactor Pilot Program.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the federal securities laws. Forward-looking statements include, but are not limited to, statements regarding Deep Fission’s business strategy, technology development plans, potential commercial deployments, potential demand represented by non-binding LOIs, expected regulatory activities, planned project milestones, potential commercialization, potential revenue recognition, and the timing, feasibility, scalability, safety, and performance of the Company’s technology. These statements are based on current expectations and assumptions and are subject to risks and uncertainties that could cause actual results to differ materially from those expressed or implied.

Important factors that may cause actual results to differ materially include, among others, risks related to the Company’s early stage of development; the non-binding nature of the LOIs; the Company’s ability to negotiate and enter into definitive commercial agreements; technical, engineering, drilling, construction, regulatory, licensing, financing, supply chain, and deployment risks; the Company’s ability to obtain required approvals from the NRC, DOE, and other governmental authorities; market adoption of the Company’s technology; and the other risks described under “Risk Factors” and “Cautionary Note Regarding Forward-Looking Statements” in Deep Fission’s filings with the Securities and Exchange Commission.

Forward-looking statements speak only as of the date of this press release. Deep Fission undertakes no obligation to update any forward-looking statements, except as required by law.