goingcritical:aalo-xUnited States · Microreactor

Aalo-X

Status: Critical since July 4, 2026 ? 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. Operating 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.

Developer: Aalo Atomics

Site: Idaho National Laboratory (adjacent to Materials and Fuels Complex), Idaho Falls, Idaho

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Details

Design	Sodium-cooled, LEU uranium-dioxide-fueled experimental reactor (XMR / Critical Test Reactor for the 10-MWe Aalo-1)
Capacity	10 MW (thermal where reported)

Milestone history

1. Announced August 12, 2025
2. Construction start August 2025
3. Fuel load —
4. First criticality July 4, 2026