US firm names nuclear reactor it plans to bury a mile underground

Deep Fission, a California-based nuclear energy startup, has officially named its innovative underground small modular reactor the Gravity Nuclear Reactor. This system will be buried one mile underground inside a narrow borehole, leveraging Earth’s natural forces—particularly gravity and the high-pressure environment created by surrounding bedrock and water—to enhance safety, reduce costs, and speed deployment. The reactor uses a standard pressurized water design fueled by low-enriched uranium, benefiting from existing supply chains and industry-proven drilling techniques from oil, gas, and geothermal sectors. Deep Fission claims this approach could cut project costs by up to 80% compared to traditional nuclear plants, with construction potentially completed in about six months and a targeted Levelized Cost of Electricity between $50 and $70 per megawatt hour. The underground placement serves as a natural containment system, aiming to minimize above-ground hazards such as weather events, aircraft impacts, and accidents. Steam generated underground is transferred via a closed loop to surface turbines, maintaining operational safety.