---
schema_version: "secwatch.filing_event.v1"
accession: "0001104659-26-109201"
form_type: "8-K"
ticker: "FISN"
cik: "0001918102"
company_name: "DEEP FISSION, INC."
filed_at: "2026-09-21T15:26:05+00:00"
generated_at: "2026-09-21T15:27:22.247832+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.5
calibrated_materiality_score: 0.5
confidence: "high"
source: SEC EDGAR
---

# Deep Fission completes borehole demo with Youngquist; targets 2027 deployment

## Summary
- Collaborated with drilling contractor Youngquist Brothers to evaluate/test deep, large-diameter borehole drilling for underground reactor deployment.
- On Sept 3, 2026, in Fort Myers FL, Deep Fission lowered and retrieved its 30-inch full-size prototype reactor canister into a 34-inch borehole to ~100 ft.
- Youngquist has drilled large-diameter boreholes to depths >8,000 ft since 1971; partnership applies that expertise to Deep Fission's Gravity™ reactor model.
- Company targets commercial deployment as early as 2027; collaboration to continue on drilling and testing.

## SEC filing metadata
- accession: 0001104659-26-109201
- form_type: 8-K
- ticker: FISN
- cik: 0001918102
- company_name: DEEP FISSION, INC.
- filed_at: 2026-09-21T15:26:05+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.5
- calibrated_materiality_score: 0.5
- confidence: high
- sec_items: 7.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1918102/000110465926109201/0001104659-26-109201-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1918102/000110465926109201/tm2625786d1_8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001104659-26-109201
- JSON: https://secwatch.observer/filing/0001104659-26-109201.json
- Plain text: https://secwatch.observer/filing/0001104659-26-109201.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.