goingcritical:deep-fission-gravityUnited States · SMR
Deep Fission Gravity (DB-1)
Status: Under construction target criticality 2027 (confidence: low) Reactor status full glossary → Announced Publicly announced — a site and design are proposed, but construction has not begun. Site preparation Early site and civil works are under way; the first safety-related ("nuclear") concrete has not yet been poured. Under construction Formal construction has begun, marked by the first nuclear concrete. Fuel loaded Nuclear fuel has been loaded into the core. The reactor is fuelled but has not yet gone critical. Critical Has reached first criticality — a self-sustaining chain reaction, usually at low power — but is not yet connected to the grid. Grid connected Synchronised to the electrical grid and exporting power for the first time, but still in commissioning and power-ascension testing — not yet in commercial service. In commercial operation — the operator has formally declared the unit in regular commercial service. Shut down Permanently shut down and no longer generating; may be defuelled, undergoing decommissioning, or preserved in place. Canceled Abandoned before completion.
Site: Parsons, Kansas
Underground borehole PWR concept; first test well drilled to 6,000 feet in 2026 (DOE OTA signed Dec 2025)
Company targets full-power operations in H1 2027 and commercial deployment in H2 2027 or early 2028; no separate criticality date stated
Details
| Design | Deep Fission Borehole Reactor — 15-MWe pressurized water reactor operated roughly one mile underground in a borehole |
| Electrical output | 15 MWe |
Milestone history
- Announced August 12, 2025
- Construction start December 2025
- Fuel load —
- First criticality target 2027
- Grid connection —
- Commercial operation —