Deep Fission, Inc. is an advanced nuclear energy company currently developing small, pressurized-water reactors that operate deep underground. The U.S. Department of Energy (DOE) approved the Nuclear Safety Design Agreement for the company’s Gravity Nuclear Reactor.

This approval creates the safety framework for the reactor’s future, which marks a huge regulatory milestone for the company. It also confirms the reactor design is ready to move forward under the DOE’s Reactor Pilot Program. Deep Fission is now heading into the next phase of the DOE authorization pathway, then eventually demonstrating and deploying this underground tech.

“This approval is a major step forward for Deep Fission,” said Liz Muller, co-founder and CEO of Deep Fission. “We believe our mile-deep design gives us the ability to move faster in the stages ahead.”

Developing the Commercial Project in Kansas

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A rendering of the Deep Fission gravity reactor; Photo: Deep Fission

Deep Fission is working on a commercial pilot project at the Great Plains Industrial Park in Parsons, Kansas. It broke ground back in December 2025. Since then, the team has drilled its first data acquisition well down to 6,000 feet. The company also recently delivered a prototype reactor canister right to the site.

Right now, the company is moving through a proof-of-concept program. This involves drilling large-diameter wells and hitting prototype installation milestones.

The Parsons project isn’t just a one-time criticality test. After initial testing and getting DOE authorization, the company wants the demonstration reactor to become a fully licensed, commercial unit pumping out power. It plans to get that license from the Nuclear Regulatory Commission. Deep Fission wants to build a direct, credible path from showing the tech works to actually using it commercially.

Deep Fission will keep working closely with the DOE as the reactor design moves through the next rounds of review and authorization.