DOE Approves Deep Underground Nuclear Reactor for Commercial Pilot

Deep Fission, a California-based company, has secured key regulatory approval from the U.S. Department of Energy (DOE) for its underground small modular reactor (SMR) concept, known as the Gravity reactor. The DOE’s clearance of the Nuclear Safety Design Agreement (NSDA) marks a significant milestone, allowing the company to advance its project under the federal Reactor Pilot Program. The Gravity reactor employs conventional pressurized water reactor technology but places it approximately one mile below the surface in a deep borehole. This approach aims to simplify deployment, reduce above-ground infrastructure size, and leverage proven technology in a novel configuration. While the approval establishes a regulatory foundation for continued design work and future testing, it does not authorize reactor operation. Deep Fission plans to conduct additional technical reviews before seeking authorization for its demonstration unit. Construction activities are ongoing at the Parsons, Kansas site, with crews drilling a 6,000-foot data acquisition well and delivering a prototype reactor canister. The company intends to transition the demonstration reactor into a licensed commercial power plant, aligning with goals of the Reactor Pilot Program and Executive Order 14301 to accelerate advanced nuclear technology deployment. If successful, this project could introduce a new model for deploying reactors by reducing surface footprint while using established pressurized water reactor technology.