Deep Fission Secures DOE Approval for Gravity™ Nuclear Reactor Safety Design, Advancing Commercial Deployment
Deep Fission, Inc. (Nasdaq: FISN), an advanced nuclear technology company developing next-generation small modular pressurized water reactors (SMRs) designed for installation approximately one mile underground, has achieved a significant regulatory milestone after receiving approval of its Nuclear Safety Design Agreement (NSDA) from the U.S. Department of Energy (DOE). The approval marks a critical advancement for the company’s proprietary Gravity™ Nuclear Reactor and positions the project to move forward under the DOE’s Reactor Pilot Program.
The DOE’s decision represents an important validation of Deep Fission’s innovative underground reactor concept and confirms that the company’s reactor design has met the necessary criteria to proceed through the next phases of federal review. The approval establishes the safety framework that will guide continued engineering, testing, and regulatory development as Deep Fission works toward demonstration and eventual commercial operation of its unique nuclear energy system.
Major Regulatory Milestone
Receiving approval for the Nuclear Safety Design Agreement is one of the most important steps in the DOE authorization process for advanced nuclear technologies. The agreement outlines the safety principles, engineering expectations, and technical review process that will govern future stages of the reactor’s development.
By securing this approval, Deep Fission has demonstrated that its reactor concept is sufficiently mature to continue progressing through the Department of Energy’s Reactor Pilot Program. The program is designed to accelerate the deployment of advanced nuclear technologies capable of strengthening the nation’s clean energy infrastructure while maintaining rigorous safety standards.
The approval also reflects increasing federal interest in supporting innovative nuclear technologies that can provide reliable, carbon-free electricity for growing industrial, commercial, and grid-scale energy demands.
With the NSDA now in place, Deep Fission will continue advancing through the DOE’s structured authorization pathway, including additional engineering reviews, technical evaluations, and demonstration activities before commercial deployment.
Advancing an Underground Nuclear Reactor Concept
Unlike conventional nuclear power plants that are constructed at the surface, Deep Fission has developed a novel approach that places small modular pressurized water reactors roughly one mile beneath the Earth’s surface inside specially drilled wells.
The company’s Gravity™ Nuclear Reactor is intended to leverage natural underground conditions to improve operational efficiency and enhance inherent safety characteristics while reducing the overall surface footprint typically associated with nuclear generating facilities.
Installing reactors deep underground offers several potential advantages, including:
- Enhanced physical security
- Reduced construction footprint
- Passive geological protection
- Simplified containment concepts
- Lower visual and environmental impact
- Potential cost reductions through modular deployment
Rather than constructing massive above-ground containment buildings, the reactor is designed to utilize deep geological formations as part of its overall safety strategy.
Deep Fission believes this approach could enable faster deployment timelines while addressing several challenges traditionally associated with conventional nuclear construction.
CEO Highlights Importance of DOE Decision
Deep Fission co-founder and Chief Executive Officer Liz Muller described the DOE approval as an important achievement for the company and its long-term commercialization strategy.
According to Muller, the regulatory milestone validates years of engineering work and provides a clear pathway for moving the Gravity™ Nuclear Reactor through the next stages of development.
She emphasized that the company’s mile-deep reactor design offers significant advantages during future project phases and could allow Deep Fission to progress efficiently toward demonstration and commercial operation.
The approval also reinforces the company’s confidence that underground nuclear technology can become a practical solution for future clean electricity generation.
Reactor Pilot Program Accelerates Innovation
The Department of Energy’s Reactor Pilot Program was established to help accelerate deployment of advanced reactor technologies capable of supporting America’s future energy needs.
Rather than following only traditional regulatory timelines, the program allows qualified developers to work closely with the DOE throughout reactor design, testing, and demonstration while maintaining rigorous safety oversight.
Participation in the program enables companies such as Deep Fission to receive structured technical guidance and regulatory coordination as they advance increasingly sophisticated reactor technologies.
The NSDA serves as one of the foundational elements of that process, defining safety expectations before more advanced development activities begin.
For Deep Fission, approval under the program represents both technical validation and an opportunity to shorten the path toward commercial deployment.
Progress Continues at Kansas Demonstration Site
While regulatory work advances in Washington, Deep Fission has continued making significant progress at its commercial pilot location within the Great Plains Industrial Park in Parsons, Kansas.
The site serves as the company’s primary demonstration facility and will showcase the feasibility of its underground nuclear reactor concept.
Construction activities officially began in December 2025, marking the transition from engineering design into physical project execution.
Since then, the company has completed several notable milestones.
One of the first achievements was drilling an initial data acquisition well reaching approximately 6,000 feet underground. The well provides valuable geological information that supports engineering analysis, validates drilling methods, and helps optimize future reactor installation.
Deep Fission has also delivered a prototype reactor canister to the Kansas site, representing another important step toward demonstrating the underground deployment concept.
These accomplishments provide critical experience before construction of the full demonstration reactor.
Proof-of-Concept Program Moves Forward
The company is now advancing its proof-of-concept program through a series of carefully planned engineering activities.
Upcoming work includes:
- Large-diameter well drilling
- Prototype system installation
- Underground equipment testing
- Engineering validation
- Operational readiness assessments
Each phase is intended to reduce technical risk while confirming that the underground reactor system performs as designed under real-world conditions.
The proof-of-concept program will provide important operational data that supports subsequent licensing activities and eventual commercial deployment.
Successful completion of these milestones will further demonstrate that Deep Fission’s innovative underground approach can be scaled into commercially viable nuclear generating facilities.
Designed for Commercial Operation
A distinguishing feature of the Parsons project is that it is intended to become a fully operational commercial nuclear facility rather than serving solely as an experimental test reactor.
Deep Fission has emphasized that its demonstration reactor is designed to transition directly into commercial electricity production following successful testing and regulatory authorization.
This strategy aligns with the objectives of Executive Order 14301 and the Department of Energy’s Reactor Pilot Program, both of which encourage accelerated commercialization of advanced nuclear technologies.
Instead of constructing a temporary research reactor that would later be decommissioned, Deep Fission intends for its demonstration facility to remain in service as a licensed commercial power plant.
Following initial testing and DOE authorization, the company plans to obtain a full operating license from the Nuclear Regulatory Commission (NRC), allowing the reactor to generate electricity for customers on a long-term basis.
This approach provides a more efficient pathway from research and demonstration to commercial deployment while maximizing the value of the initial investment.
Building a Path Toward Commercial Deployment
Deep Fission views the Parsons project as the first step in establishing a scalable platform for future underground nuclear facilities.
If successful, the technology could potentially be deployed at industrial sites, remote energy locations, data centers, manufacturing facilities, and utility-scale power generation projects requiring reliable, carbon-free electricity.
The growing demand for continuous power—driven by electrification, artificial intelligence, advanced manufacturing, and expanding digital infrastructure—has increased interest in advanced nuclear technologies capable of providing dependable baseload electricity.
Small modular reactors have emerged as one of the most promising solutions because they offer flexible deployment options, enhanced safety features, and reduced construction timelines compared to traditional large nuclear plants.
Deep Fission’s underground design adds another layer of innovation by reimagining how nuclear reactors are installed and operated.
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