Day & Zimmermann, Deep Fission Partner to Build Underground Small Modular Reactor

PHILADELPHIA, June 2, 2026 /PRNewswire/ -- Day & Zimmermann (D&Z) and Deep Fission, Inc. (Deep Fission) announced today their partnership in the construction of Deep Fission's Gravity Nuclear Reactor, the company's proprietary underground nuclear reactor. Deep Fission is an advanced nuclear energy company developing small modular pressurized water reactors installed one mile underground. D&Z, an engineering, procurement, and construction (EPC) company and leader in the nuclear power industry, will oversee the project's pre-construction planning and perform above-ground construction.

"Deep Fission's advanced reactor technology, combined with Day & Zimmermann's quality program and nuclear expertise, will bring first-of-a-kind nuclear construction to reality," said Ross McConnell, D&Z Chief Nuclear Officer. "For more than 40 years, the power industry has trusted our operational discipline and process-driven approach to quality, safety, and project execution while reliably and safely navigating the Nuclear Regulatory Commission's complex oversight. Our partnership with Deep Fission reflects our continued leadership in advancing nuclear technology, and we're excited to move this project forward together."

"Partnering with Day & Zimmermann will bring proven nuclear construction expertise and execution discipline to Deep Fission's deployment," said Mike Brasel, Chief Operating Officer at Deep Fission. "Their track record supports our aim to deliver a new model for low-carbon, reliable power that is simpler to build, inherently safe, and scalable to meet growing energy demand."

The project site is located at the Great Plains Industrial Park in Parsons, Kansas, and is part of the U.S. Department of Energy (DOE) Reactor Pilot Program. Deep Fission is one of 10 companies selected under the program.

D&Z is among a select group of companies with not only the qualifications to perform nuclear-code work needed for expanding and modernizing the nation's nuclear energy infrastructure, but also with natural gas plant construction experience — executed under ISO 9001 quality standards — essential for building the non-nuclear, above-ground turbine generator systems of Deep Fission's Gravity reactor. In addition, D&Z's record of industry-leading safety performance and strong labor relations across the US delivers workforce quality, flexibility, and long-term labor solutions that support project success, even in today's tight labor market. This depth of capability positions D&Z as a trusted partner for both conventional and advanced reactor projects needed to address the massive energy demands in the U.S.

Deep Fission's reactor design integrates established pressurized water reactor technology, with novel emplacement in deep boreholes approximately one mile below the Earth's surface. Each Gravity Nuclear Reactor will leverage subsurface conditions to support key containment and operating functions, including the use of hydrostatic pressure from a water column within the borehole to support reactor operating pressure and cooling, and the surrounding geological formation to provide structural confinement and shielding, reducing the need for above-ground megastructures.

About Day & Zimmermann
D&Z's Maintenance and Construction division helps customers in power and industrial markets focus on doing their best work better by delivering safe, first-time quality maintenance, construction, engineering, and technical services. In addition to our long-standing, proven Maintenance & Modification (M&M) capabilities, we offer a suite of multidiscipline engineering, procurement, and construction (EPC) services to support large-scale, design-build projects and a total-project solution required to bring advanced nuclear projects from concept through commissioning. Plus, as a leading craft employer D&Z proudly provides long, meaningful careers to skilled craft professionals who build our future.

About Deep Fission
Deep Fission is revolutionizing the energy landscape with innovative technology that places a small modular pressurized water reactor in a borehole one mile underground. Founded and led by a team of seasoned scientists, engineers, and entrepreneurs, the company is committed to delivering safe, reliable, and affordable low-carbon power at scale. Deep Fission was selected for the Department of Energy's Reactor Pilot Program and is building its first reactor in Parsons Kansas. Deep Fission was founded in 2023 by father-daughter team Liz and Rich Muller. Learn more at deepfission.com.

Forward-Looking Statements
This press release contains forward-looking statements within the meaning of the U.S. federal securities laws, including, among other things, statements regarding Deep Fission's development plans, anticipated project timelines, potential commercial opportunities, collaboration activities, and other future matters. These statements are based on current expectations and involve risks and uncertainties that could cause actual results to differ materially from those expressed or implied. Important factors that may affect actual results are described under "Risk Factors" and "Cautionary Note on Forward-Looking Statements" in Deep Fission's Annual Report on Form 10-K filed with the U.S. Securities and Exchange Commission (as amended or supplemented), and in other filings Deep Fission makes with the SEC. Forward-looking statements speak only as of the date of this press release. Deep Fission undertakes no obligation to update any forward-looking statements, whether as a result of new information, future events, or otherwise, except as required by law.

SOURCE Day & Zimmermann