California-based start-up Deep Fission has released the completed US Department of Energy (DOE)-approved Nuclear Safety Design Agreement (NSDA) for its Gravity Nuclear Reactor. The company is the first participant in the DOE Reactor Pilot Program to voluntarily share its full safety blueprint with the public.
Deep Fission is developing advanced, small modular pressurised water reactors designed to be installed one mile underground. It uses standard, low-enriched uranium fuel. Deep Fission recently demonstrated installation and retrieval of a full-size prototype reactor canister from a borehole using standard commercial drilling equipment at the Great Plains Industrial Park in Parsons, Kansas
Deep Fission intends to transition this demonstration unit into a fully Nuclear Regulatory Commission (NRC)-licensed, commercial operating facility capable of delivering power directly to the grid. The NSDA is a critical early milestone approved by the DOE on July It establishes a rigorous safety framework that defines design requirements, safety analysis methods, and regulatory expectations for the pilot. Addition documentation and reviews are required before potential DOE authorisation for operations.
While a public release of the document is not legally mandated, the company chose to publish it to foster public trust and operational transparency. “We’re publishing our full NSDA because we think the public deserves to see the actual safety case behind this reactor, not just our word that DOE reviewed one,” said Liz Muller, CEO and Co-Founder of Deep Fission. “A project with this kind of ambition should be built in the open, and we hope more of the industry joins us in doing that.”
Unlike a standalone criticality test, the Parsons pilot is designed with the intent that the same reactor unit Deep Fission installs and brings to criticality under DOE authorisation could, subject to NRC licensing, transition to commercial power operation rather than being decommissioned once initial testing concludes.
Deep Fission said the published document includes a small number of redactions related to security-sensitive design details, consistent with standard practice for advanced reactor safety filings. “As with any live engineering and regulatory process, some elements of the design have evolved since the NSDA was first developed, and Deep Fission will share updates as its safety case advances through the next stages of DOE review.”
