Deep Fission Prototype Reactor Canister Arrives at Kansas Site, Advancing Reactor Proof-of-Concept Program

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Key Terms

pressurized water reactor technical

A pressurized water reactor is a type of nuclear power plant that uses water kept under high pressure to carry heat away from the nuclear core without letting it boil; that hot water then passes through a heat exchanger to make steam that drives turbines to produce electricity. Think of it like a sealed pressure cooker transferring heat into a separate steam system. Investors care because this design influences construction and operating costs, safety and regulatory risk, fuel and maintenance needs, and long-term liabilities such as decommissioning—factors that affect a plant’s profitability and investment risk.

borehole technical

A borehole is a drilled hole made into the ground or seabed to reach subsurface layers for exploration, sampling, or to install equipment such as wells, pumps or monitoring instruments. For investors, boreholes matter because they generate direct information about underground resources, engineering conditions and regulatory compliance—like taking core samples or geotechnical readings—so their number, depth and results help measure project progress, costs and risks.

closed-loop system technical

A closed-loop system is an automated setup that continuously measures its own output and uses that feedback to adjust inputs without human intervention, like a thermostat that senses room temperature and turns heating on or off. Investors care because closed-loop designs can improve performance, reduce operating costs and human error, and create harder-to-replicate products or services, affecting efficiency, regulatory scrutiny, liability, and competitive advantage.

reactor pilot program regulatory

A reactor pilot program is a small-scale, first-of-a-kind project that builds and operates a prototype power reactor or reactor system to test its design, safety systems, permitting and real-world costs before wider commercial deployment. For investors it matters because pilot programs reduce technical and regulatory uncertainty, reveal true construction and operating costs, and set the timeline for possible revenue — much like a prototype car that proves a new model works before mass production.

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07/07/2026 - 07:00 AM

-- Company Prepares to Ring Nasdaq Closing Bell Today in Honor of Milestone --

PARSONS, Kan.--(BUSINESS WIRE)-- Deep Fission, Inc. (Nasdaq: FISN) (“Deep Fission” or the “Company”), an advanced nuclear energy company developing small modular pressurized water reactors installed one mile underground, today announced the arrival of its prototype reactor canister at its Parsons, Kansas site, marking a key milestone in the Company’s Proof-of-Concept Well program and its Gravity Nuclear Reactor™ development. In celebration of this milestone and its listing on the Nasdaq Stock Market, Deep Fission will ring the Nasdaq closing bell today at 4:00 PM ET.

Deep Fission Reactor Canister

The factory-built prototype canister completed fabrication, hydrostatic testing, and delivery to Kansas, representing tangible progress toward validating installation, infrastructure readiness, and operational sequencing for the Company’s first commercial demonstration well.

“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. Upcoming testing using this hardware will validate our approach and provide valuable learnings as we assemble, install and test key systems under non-nuclear conditions in our large diameter borehole.”

The Proof-of-Concept Well is Deep Fission’s nearly full-scale validation program, designed to demonstrate a larger-diameter borehole and end-to-end installation workflow using commercial-grade, non-nuclear components prior to fuel loading. The program is intended to validate each stage of underground deployment under real-world conditions while confirming engineering assumptions at scale and supporting the Company’s broader commercialization timeline.

The reactor canister is a key component of Deep Fission’s Gravity Nuclear Reactor™ design, which places a small modular pressurized water reactor in a borehole approximately one mile underground. The Gravity Reactor™ is based on established pressurized water reactor technology adapted for subsurface deployment, using pressure from a mile-long water column atop and surrounding the reactor in the borehole, to support operating pressure and cooling. In this design, thermal energy is transferred through a closed-loop system from the reactor canister to a heat exchanger, then rises to the surface in a secondary closed-loop for conversion into electricity, like a geothermal system.

Following arrival at the Parsons site, the non-nuclear prototype reactor canister will be prepared for testing as Deep Fission continues preparation for its large diameter drilling program. The Company is advancing permitting with the Kansas Department of Health and Environment (KDHE) for the non-nuclear borehole, which is expected to serve as the next major proof-of-concept milestone.

“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.

The Company is also progressing development of its full-scale nuclear demonstration borehole and advancing design of its primary heat exchanger. These parallel efforts support a phased strategy to accelerate iterative validation of the most unique aspects of Deep Fission’s commercial deployment model.

Deep Fission is participating in the U.S. Department of Energy’s Reactor Pilot Program. Authorized under Executive Order 14301, the program enables reactor testing and deployment in order to accelerate the path to commercialization of nuclear energy.

Tune in to Deep Fission ringing the Nasdaq closing bell today at https://www.nasdaq.com/marketsite/bell-ringing-ceremony

About Deep Fission

Deep Fission is developing technology that places a small modular pressurized water reactor in a borehole approximately one mile underground. The Company’s Gravity Nuclear Reactor™ approach combines established pressurized water reactor technology with a novel underground deployment model designed to simplify construction, enhance safety, and support scalable commercial deployment. Deep Fission is focused on delivering reliable, low-carbon baseload power to meet growing electricity demand from utilities, industrial customers, and data centers. The Company is currently advancing the development of its first reactor project in Parsons, Kansas and was selected for the U.S. Department of Energy’s Reactor Pilot Program.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the federal securities laws. Forward-looking statements include, but are not limited to, statements regarding Deep Fission’s business strategy, technology development plans, potential commercial deployments, potential demand represented by non-binding LOIs, expected regulatory activities, planned project milestones, potential commercialization, potential revenue recognition, and the timing, feasibility, scalability, safety, and performance of the Company’s technology. These statements are based on current expectations and assumptions and are subject to risks and uncertainties that could cause actual results to differ materially from those expressed or implied.

Important factors that may cause actual results to differ materially include, among others, risks related to the Company’s early stage of development; the non-binding nature of the LOIs; the Company’s ability to negotiate and enter into definitive commercial agreements; technical, engineering, drilling, construction, regulatory, licensing, financing, supply chain, and deployment risks; the Company’s ability to obtain required approvals from the NRC, DOE, and other governmental authorities; market adoption of the Company’s technology; and the other risks described under “Risk Factors” and “Cautionary Note Regarding Forward-Looking Statements” in Deep Fission’s filings with the Securities and Exchange Commission.

Forward-looking statements speak only as of the date of this press release. Deep Fission undertakes no obligation to update any forward-looking statements, except as required by law.