DOE approves Aalo-X safety analysis, reactor nears criticality milestone

The U.S. Department of Energy’s Idaho Operations Office has approved the documented safety analysis for Aalo Atomics’ Aalo-X Critical Test Reactor, pushing the project into its final pre-operations phase and closer to an operational readiness review. For a startup reactor, that is a major gate: the documented safety analysis is the authoritative safety basis for a DOE nuclear facility, the core document that lays out how the plant is meant to operate through normal running, off-normal events, and accidents.

That matters because Aalo-X is not a commercial plant sitting in the NRC licensing lane. It is an experimental reactor on DOE land, and the company has said the DOE pathway is rigorous in the same way a commercial licensing process is rigorous, even if the regulator is different. The approval also moves Aalo closer to first criticality on a schedule that has been compressed by design. DOE’s reactor pilot program is aiming to get at least three advanced reactor concepts outside the national laboratories to criticality by July 4, 2026, and Aalo has said it is working toward that same milestone.

DOE identified a tentative site for the reactor at Idaho National Laboratory on December 10, 2024, and later paperwork described the project as an Aalo-X facility and reactor experiment near the Materials and Fuels Complex on about a 1-acre parcel south of the MFC boundary. Aalo has described Aalo-X as a 10-MW sodium-cooled experimental reactor meant to validate the company’s technology at full scale before future commercial deployment. The critical test reactor is designed to test the full-scale nuclear core for the planned power reactor that will sit next door, with the fuel, moderator, control rod drive mechanisms, shielding, and instrumentation systems all intended to mirror the commercial design.

Aalo has already stacked up several hardware milestones. The company said it completed construction of the Aalo-X critical test reactor in March 2026, after reports that five reactor test modules had been shipped to Idaho National Laboratory in late 2025. It also said Urenco would deliver enriched uranium in late 2025 or early 2026, and Baker Hughes was selected to provide a 10 MWe steam turbine generator set and associated ancillary systems for Aalo-X. The company’s broader commercial roadmap centers on Aalo Pods for data centers at hundred-megawatt scale, while Aalo has also pointed to municipal utilities, desalination, and industrial process heat as target markets. Led by co-founder and CEO Matt Loszak, the company is trying to turn a test reactor into proof that its microreactor pitch can move from paper to hardware, and from hardware to deployment, on DOE ground.