Deep Fission, a Berkeley-based start-up, is developing mile-deep small modular reactors in Utah, leveraging underground PWR technology to reduce costs, enhance safety, and address rising global uranium demand.
Deep Fission, a start-up developing small modular pressurized-water reactors installed a mile underground, announced this week that Utah is one of three states where it has signed Letters of Intent for joint development projects.
Based in Berkeley, California, Deep Fission was founded in 2023 by physicist Richard Muller, an emeritus professor at UC Berkeley, and his daughter Elizabeth “Liz” Muller, a serial entrepreneur who co-founded the nuclear waste startup Deep Isolation and the climate-data nonprofit Berkeley Earth (both based in Berkeley, CA), a nonprofit organization focused on environmental data science and analysis. Liz Muller serves as CEO, while her father is chief technology officer, combining her entrepreneurial experience with his decades of research in physics and nuclear science.
“We’re proud to collaborate with our partners in Texas, Utah, and Kansas,” Liz Muller said. “Together, we’re laying the groundwork for the next era of nuclear energy in the United States.”
Deep Fission’s technology adapts conventional pressurized-water reactor (PWR) designs to an underground setting. The company places off-the-shelf reactor components and low-enriched uranium in a large-diameter borehole a mile below the surface. Heat from fission in the reactor core is transferred via water to a secondary loop at the surface, where it powers turbines. The surrounding rock provides natural shielding and containment, reducing the surface footprint and eliminating the need for massive concrete domes. Passive cooling through the rock can mitigate overheating, while the surface infrastructure is minimal, resembling a geothermal or natural gas facility.
At the end of its operational life, the reactor may be dismantled and removed or sealed underground. While this approach could significantly reduce construction costs and use proven reactor technology, challenges remain in drilling, groundwater protection, and regulatory acceptance. The company projects an overnight capital cost advantage of 70–80% over conventional reactors and a levelized cost of electricity of 5–7¢ per kilowatt-hour.
Utah is a logical candidate for Deep Fission’s first projects due to two key factors: the Intermountain Power Project (IPP) near Delta and the DOE FORGE research site near Milford. The IPP site already has high-capacity transmission infrastructure and has been considered for advanced reactors, while FORGE offers decades of deep-drilling and rock characterization data in crystalline basement — critical for safely hosting a mile-deep borehole reactor.
A recent Salt Lake Tribune report highlights both the promise and challenges of nuclear development in rural Utah. While state and corporate actors emphasize low-carbon power and economic benefits, local officials in Millard County have expressed concerns about tax revenue sharing, project scale, and the uncertainties of emerging reactor technologies. Successful siting, the article notes, will require careful community engagement, transparent communication, and realistic timelines.
On September 5, 2025, Deep Fission, Inc. completed an alternative public offering (APO) commonly referred to as a “reverse merger” with Surfside Acquisition Inc., a public shell corporation. As a result of the transaction, Deep Fission changed its name to Deep Fission Nuclear, Inc. and became a wholly owned subsidiary of Surfside, which changed its name to Deep Fission Inc.
According to Deep Fission’s website, Deep Fission Inc. plans to confirm its first site in 2025, submit a licensing application in 2026, and obtain construction and operation approval by 2028, targeting commercial operation in Fall 2029. The schedule depends on regulatory approval, local government support, and successfully navigating the technical and environmental challenges of an underground reactor in Utah and its other proposed sites.
The company told TechBuzz it was not able to disclose the partner or the precise site in Utah at this time. TechBuzz will follow up and report specific details of the Utah site and partners at a later date.
Global demand for uranium is projected to increase significantly in the coming decades, underscoring the importance of developing efficient and scalable nuclear technologies. According to the World Nuclear Association's 2023 Nuclear Fuel Report, uranium demand for nuclear reactors is expected to climb by 28% by 2030, reaching approximately 83,840 metric tons annually, up from 65,650 tons in 2023. This surge is driven by an anticipated 18% rise in nuclear reactor capacity during the same period. Looking further ahead, demand is projected to nearly double by 2040, exceeding 150,000 metric tons per year.
This escalating demand presents both challenges and opportunities for the nuclear industry. While traditional uranium mining and enrichment processes are expected to meet short-term needs, the long-term supply may face constraints due to the lengthy development timelines for new mining projects. The World Nuclear Association emphasizes the necessity for timely investment in exploration and the development of new uranium sources to avoid potential supply gaps.
In this context, innovative reactor designs, such as Deep Fission's underground small modular reactors, offer a promising solution. By utilizing off-the-shelf pressurized-water reactor components and low-enriched uranium, these reactors aim to reduce construction costs and minimize surface land use. Their underground configuration also enhances safety and security, addressing public concerns associated with traditional nuclear facilities. As the demand for uranium continues to rise, technologies that optimize fuel use and reduce environmental impact will play a crucial role in the sustainable expansion of nuclear energy.
To learn more about the company, visit deepfission.com.