Faulty reasoning signals

• Confirmation Bias - 0%
• Anchoring Bias - 0%
• Availability Heuristic - 4.5% (23 hits)
• Representativeness Heuristic - 12.1% (62 hits)
• Hindsight Bias - 0%
• Overconfidence Bias - 3.1% (16 hits)
• Framing Effect - 3.9% (20 hits)
• Loss Aversion - 0%
• Status Quo Bias - 0%
• Sunk Cost Effect - 10.6% (54 hits)
• Optimism Bias - 25.2% (129 hits)
• Pessimism Bias - 0%

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US startup moves one-mile underground reactor closer to reality with key prototype

California-based advanced nuclear energy company Deep Fission has delivered the prototype reactor canister for its underground small modular reactor system to its test site in Parsons, Kansas, marking a key step toward validating its unconventional nuclear power concept.

The factory-built canister will be used in the company’s Proof-of-Concept Well program, a nearly full-scale demonstration designed to test installation methods, infrastructure readiness, and operating procedures before any nuclear fuel is introduced.

Unlike conventional small modular reactors, Deep Fission’s design places a pressurized water reactor inside a borehole about one mile underground.

The company says the approach could simplify construction while using the surrounding water column to help maintain operating pressure and cooling.

The prototype has completed fabrication, hydrostatic testing, and delivery, allowing the company to move into the next phase of non-nuclear testing as it prepares for large-diameter drilling at the Kansas site.

## Underground reactor design

“The arrival of our prototype reactor canister at the Kansas site is a clear step forward in moving from design to deployed infrastructure,” said Mark Pérès, Chief Nuclear Officer of Deep Fission.

“Successfully manufacturing, testing, and delivering this hardware demonstrates performance of our design and supply chain capabilities.”

The Proof-of-Concept Well is intended to validate the complete deployment sequence using commercial-grade, non-nuclear equipment.

The company plans to test how the canister is assembled, lowered into the borehole, installed, and integrated with supporting infrastructure under real-world conditions.

The demonstration is designed to verify engineering assumptions before construction of the company’s first nuclear demonstration well, reducing technical risk ahead of commercial deployment.

Deep Fission’s Gravity Nuclear Reactor uses established pressurized water reactor technology but deploys it in a vertical borehole approximately one mile deep.

Instead of relying solely on conventional reactor vessels and containment structures, the design uses the pressure generated by a mile-long water column surrounding the reactor to support reactor operating pressure while also providing cooling.

Heat generated by the reactor is transferred through a closed-loop system to a heat exchanger before traveling back to the surface through a secondary loop, where it can be converted into electricity using equipment similar to conventional geothermal power plants.

## Testing before fuel

Following delivery, the prototype canister will undergo additional testing while the company advances permitting for its non-nuclear borehole with the Kansas Department of Health and Environment.

The borehole is expected to become the next major milestone in demonstrating the technology.

“This milestone reflects disciplined execution across fabrication, testing, and delivery, and strengthens the foundation for scaled deployment of our Gravity Nuclear Reactor™ system,” said Mike Brasel, Chief Operating Officer of Deep Fission.

Alongside the proof-of-concept program, the company is continuing work on a full-scale nuclear demonstration borehole and the design of its primary heat exchanger.

These efforts are intended to validate the unique aspects of its underground deployment strategy before commercial operation.

Deep Fission is also participating in the U.S.

Department of Energy’s Reactor Pilot Program, which was authorized under Executive Order 14301 to accelerate reactor testing and commercialization of advanced nuclear technologies.