Deep Fission ($FISN): a Money Pit

Deep Fission's pitch to power AI data centers depends on drilling a water-filled nuclear reactor one mile through hard rock into a borehole up to 60 inches wide, roughly six times the diameter typical of deep oil, gas, and geothermal wells.

The company once told investors its electricity would cost $50-70/MWh, a figure that vanished from its materials around its June 2026 Nasdaq listing. Iceberg Research, in a report examining Deep Fission's filings, presentations, and regulatory record, calculates the company's actual levelized cost at $148-289/MWh using its own prospectus assumptions, well above the $103-110/MWh estimated for the gas generation that dominates current data-center deals. The report's position in FISN is not specified in the materials reviewed.

Ticker: FISN (Deep Fission, Inc.)
Research Firm: Iceberg Research
Report URL: https://iceberg-research.com/2026/09/24/deep-fission-fisn-a-money-pit/?ref=shortreport.fyi
Report date: 2026-09-24
Position Disclosure: Not specified in the materials reviewed.

Thesis

Iceberg Research argues that Deep Fission's own disclosures undermine its central pitch of cheaper, faster nuclear power for AI data centers.

Vanishing Cost Target: FISN's January 2026 presentation guided to $50-70/MWh, but that target disappeared from its June 2026 IPO prospectus and later materials. Using the company's own prospectus assumptions and Lazard's 7.7% discount rate, the author calculates $289/MWh for its first reactor and $148/MWh for later units, roughly 200% above the original guidance and still above the $103-110/MWh estimated cost of gas-fired data-center generation.
Optimistic Cost Curve: FISN assumes a 45% capital-cost drop from its $152 million first reactor to an $84 million later unit. Benchmarked against TVA's 49% industry-wide FOAK-to-NOAK decline, the author calculates a $112 million cost, 34% above FISN's figure, implying a $170/MWh levelized cost.
Growing Borehole, Rising Cost: The reactor's required borehole grew from an original 30-inch design for 15MWe, to 42 inches for 8MWe, to the CEO's latest figures of 40 inches for 5MWe and 60 inches for 15MWe, while FISN's financial projections still assume 42-inch and 50-inch holes.
Missed Criticality, Slow Pilot: FISN dropped its July 2026 criticality target while four DOE pilot-program peers reached criticality by that month. Its Nuclear Safety Design Agreement took nearly a year to clear versus roughly three months for peer Antares, and it now targets NRC approval in 2H 2027, a timeline the report contrasts with NuScale's 74-month certification history.
Unresolved NRC Concerns: NRC staff feedback from 2024 flagged Deep Fission's use of geology as containment and heat sink, disposal-pathway uncertainty, and neutron leakage, and challenged the basis for drilling and emplacement within days or weeks by citing far longer geological investigations at Yucca Mountain. FISN's claimed six-month deployment also conflicts with the two-year development timeline stated in its own prospectus.
Non-Binding Pipeline: Of FISN's announced 18.5GW customer pipeline, only about 4GW is tied to identified counterparties. The Great Plains Industrial Park letter of intent for up to 2GW is non-binding, and the park reported just $219,000 and $197,000 of revenue in March and April 2026. The Blue Owl and Endeavour arrangements are similarly non-binding, with no commitments to purchase power, finance, or build.
Looming Funding Gap: FISN's June 2026 10-Q disclosed substantial doubt about its ability to continue as a going concern, with roughly $93 million of cash against an estimated $443 million of spending needs through 2027. The author calculates a $350 million funding gap and roughly 43% dilution at the current share price, arriving as nine SMR stocks compete for capital versus three a year earlier.
Repackaged Waste Venture: Deep Fission's founders spent roughly a decade on Deep Isolation, a borehole-based nuclear-waste-disposal company that never commercialized its concept; 59% of its 2025 revenue came from an acquired environmental consulting subsidiary rather than its core business.

Catalysts

NRC license application and approval targets: The company targets a license application in 1H 2027 and approval in 2H 2027; outcomes will test or further undercut FISN's licensing timeline claims.
Cash runway under 12 months: Per FISN's June 2026 10-Q, any equity raise would reveal the scale of dilution shareholders face.
DOE Reactor Pilot Program milestones: Following the August 2026 Nuclear Safety Design Agreement, execution pace will show whether licensing can accelerate as the company claims.
Great Plains pilot buildout dependency: Buildout in Parsons, Kansas is contingent on the industrial park securing industrial or AI data-center demand, determining whether the flagship 2GW opportunity materializes.
Conversion of non-binding arrangements: Turning Blue Owl, Endeavour, and GPIP arrangements into binding offtake, financing, or construction commitments would validate the claimed pipeline.
Additional SMR listings: Potential listings including Westinghouse, NuCube, and ONE Nuclear could further crowd competition for investor capital.

Company Response

The report does not indicate that Deep Fission was asked for comment, and no company response to the report's findings is cited. The analysis instead draws on the company's own filings, investor presentations, press releases, videos, and public statements by CEO Elizabeth Muller and COO Mike Brasel.

Notable Details

Deep Fission's CTO and co-founder, Richard Muller, is an emeritus physics professor, not a nuclear engineer, per the report. Co-founder and CEO Elizabeth Muller said in November 2025 the company was targeting a reactor "turned on" by July 4, 2026, then later called criticality tests "science experiments" after the company missed that date.
The Wall Street Journal described the Great Plains Industrial Park site, home to Deep Fission's proposed 2GW project, as "mostly overgrown," and reported local opposition to the project.
Deep Fission cut its IPO price to $16 per share from an initial $24-26 range, according to Renaissance Capital, as the number of listed SMR stocks rose from three before October 2025 to nine.
Canaccord Genuity's July 2026 initiation report estimated Deep Fission's later-unit levelized cost at just $36/MWh; the report alleges Canaccord discounted project costs but not electricity generation, and recalculates $160/MWh using Canaccord's own 11% discount rate.

"How much is a concept worth? A lot, when you are in the middle of a bubble. But that time has clearly passed."
This appears in Iceberg Research's conclusion, after the report argues the reactor remains in conceptual and early engineering stages while its earlier cost claims disappeared.

FAQs

What is FISN stock, and how did Deep Fission go public?

Deep Fission trades as FISN on Nasdaq. It became an unquoted public company through a September 2025 reverse merger with shell company Surfside Acquisition, then listed on Nasdaq in June 2026 after cutting its IPO price to $16 per share from an initial $24-26 range, according to Renaissance Capital.

What is Deep Fission's Gravity Reactor and how is it supposed to work?

The Gravity Reactor is a 5-15 MWe miniature pressurized-water reactor the company plans to lower about one mile underground into a 40-60 inch water-filled borehole drilled into hard rock. Deep Fission's June 2026 prospectus states the reactor remains in conceptual and early engineering stages.

What does Iceberg Research allege about Deep Fission?

Iceberg Research's report argues that Deep Fission's cost, regulatory, deployment, and customer-pipeline claims are contradicted or undermined by the company's own filings, regulatory records, and counterparties' disclosed agreement terms. It concludes the stock trades on an unvalidated concept facing a near-term funding shortfall.

Why did Deep Fission drop its $50-70/MWh cost target?

The company's January 2026 presentation guided to $50-70/MWh, first tied to its earliest reactor and later repositioned as a target for later, cheaper-to-build units. That target, along with a claimed 70-80% cost advantage over new conventional reactors, no longer appears in its June 2026 prospectus or subsequent materials, per the report.

Is Deep Fission's 18.5GW customer pipeline real?

The company has announced a potential 18.5GW pipeline, but the report states only about 4GW is tied to identified counterparties, and those arrangements, including the Great Plains Industrial Park letter of intent, the Blue Owl memorandum, and the Endeavour term sheet, are all explicitly non-binding with no commitments to purchase power, finance, or build.

How much cash does Deep Fission have, and does it need to raise more?

Per its June 2026 10-Q, Deep Fission had roughly $93 million in cash and disclosed substantial doubt about its ability to continue as a going concern because existing funds would not cover operations through the following year. The report calculates a $443 million total cash need through 2027, implying a $350 million funding gap and about 43% shareholder dilution at the current share price.

When will Deep Fission know if the NRC will approve its reactor?

The company's August 2026 corporate presentation targets submitting its NRC license application in the first half of 2027 and receiving approval in the second half of 2027. The report contrasts this with NuScale's 74-month certification process and Kairos Power's 16-month construction-permit process for a test reactor, calling the timeline unprecedented.

What is Deep Fission's connection to Deep Isolation?

Deep Fission's founders, Richard and Elizabeth Muller, previously founded Deep Isolation in 2016 to commercialize deep-borehole disposal of nuclear waste, a business the report says has not been commercialized roughly a decade later. Of Deep Isolation's $6.1 million 2025 revenue, 59% came from Freestone, an acquired environmental and water-resources consulting subsidiary, not its core borehole-disposal business.

Disclaimer: This summary is not primary research and does not constitute investment advice. It is a brief overview of a detailed equity research report authored by the firm, organization, or source referenced in this article or at https://iceberg-research.com/2026/09/24/deep-fission-fisn-a-money-pit/, which contains extensive evidence, regulatory filings, and analysis; readers are encouraged to review the full report there for a comprehensive understanding. The content provided in this publication is not authored or originated by us — we act solely as a distributor and do not endorse, verify, or take responsibility for the accuracy, completeness, or reliability of the information presented. This publication is for informational purposes only and should not be construed as legal, business, investment, or tax advice. Always conduct independent due diligence and consult qualified professionals before making any decisions based on the information contained herein. We disclaim all liability for any loss or damage arising from reliance on third-party content, and the views expressed are solely those of the respective source and do not necessarily reflect our own.