goingcritical:kairos-hermes-2United States · SMR
Hermes 2
Status: Under construction target criticality 2030 (confidence: medium) 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: K-33 site, former Oak Ridge Gaseous Diffusion Plant, Oak Ridge, Tennessee
First power-producing Gen IV reactor to receive an NRC construction permit (Nov 2024); first deployment under the Kairos-Google 500 MW fleet agreement, with power sold to TVA
Kairos expects Hermes 2 to begin operations by 2030; capacity_mw reflects the "up to 50 MW" of electricity Kairos says the plant will supply to the TVA grid
Details
| Design | KP-FHR fluoride salt-cooled high-temperature reactor (power-producing demonstration) |
| Electrical output | 50 MWe |
Milestone history
- Announced —
- Construction start April 17, 2026
- Fuel load —
- First criticality target 2030
- Grid connection —
- Commercial operation —