goingcritical:oklo-plutoUnited States · Research reactor
Oklo Pluto
Status: Announced 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: Not yet announced (Idaho National Laboratory expected)
Oklo's second Reactor Pilot Program project; pursued under a strategic partnership project (SPP) with Battelle, in which Battelle retains design control (unlike the standard OTA pathway)
No site or criticality timeline announced as of July 2026; multiday plutonium fast reactor critical experiment suite completed at LANL's NCERC in December 2025 (physics tests, not the Pluto reactor itself)
Details
| Design | Plutonium-fueled fast test reactor supporting advanced fuel and component development |
| Capacity | Undisclosed |
Milestone history
- Announced August 12, 2025
- Construction start —
- Fuel load —
- First criticality —