Aalo Atomics Completes Critical Test Reactor Assembly, Expects Criticality Within Weeks

Aalo Atomics held a ceremony to unveil its completed Critical Test Reactor at Idaho National Laboratory, saying it expects the reactor to achieve criticality "well before" the 4 July deadline. The Austin, Texas-based company says it built the facility in months on what was, six months ago, an empty plot of land.

According to Aalo, "a completed reactor building stands there, constructed, equipped, and ready for operators to split atoms in the Critical Test Reactor." The company added that it "isn't waiting for the deadline" of 4 July to achieve zero-power criticality, and that the reactor will "go critical in a matter of weeks." Global Nuclear Fuel plans to deliver fabricated fuel rods to Aalo in early 2026, and those rods will power Aalo-X, Aalo's first experimental extra modular nuclear reactor.

The construction timeline behind the ribbon-cutting is striking even by commercial construction standards. Two weeks after being selected for the DOE program, the company broke ground on a plot of land at the border of Idaho National Laboratory to begin construction. CEO Matt Loszak noted at the ceremony that the project was completed nearly four months ahead of schedule: the reactor itself was built in 40 days, and the 3,600-square-foot building that houses it was completed in 36 days. Aalo put the feat in broader context, stating: "After founding Aalo in 2023 we have gone from incorporation to a physical reactor at a national lab in under three years, a timeline that was dismissed as fantasy by many in the nuclear establishment."

Aalo framed the unveiling within a longer commercial arc: "Today we unveil the Critical Test Reactor, the first new nuclear reactor at INL in 50 years. Next, our company solves the engineering challenges of extra-modular nuclear reactors. Then, we will construct a massive reactor gigafactory, which will 'productise' the nuclear industry so that we can build reactors in a matter of days. Full-power deployment to customers will happen later this decade. The foundational bricks for that future are now laid."

The CTR sits inside INL's Materials and Fuels Complex on a 1-acre parcel, and its development sequence involves more than just the one building. Back in December, Aalo had already shipped five reactor test modules for its Aalo-0 prototype to INL as part of its push toward a 2026 first criticality goal. Those non-nuclear modules are being used for integral effects tests and steam production trials, designed to prove the company's standardized manufacturing process before the radioactive Aalo-X pilot reactor begins operation. The company's roadmap runs from the Aalo-0 prototype through the 10-MW sodium-cooled Aalo-X pilot, eventually scaling to the "Aalo Pod," which combines five reactors to generate 50 MW of power for high-demand users.

On the fuel supply side, the pieces are in place. On March 3, Aalo signed fuel fabrication contracts with Global Nuclear Fuel, an affiliate of GE Vernova Hitachi Nuclear Energy. Separately, Urenco USA completed enriching the uranium hexafluoride feedstock needed for its fuel and delivered it to GE Vernova for fuel rod fabrication. The Aalo-X demonstration reactor will operate on 5%-enriched uranium dioxide low-enriched uranium.

The political context gives Aalo's schedule urgency beyond its own ambitions. Aalo was named last August by the DOE as one of 11 advanced reactor projects selected for support through its Nuclear Reactor Pilot Program, which aims to see at least three of them achieve criticality by 4 July this year. The initiative is part of the Reforming Nuclear Reactor Testing executive order signed by President Donald Trump in May. Fellow program participants include Antares Nuclear Inc, Atomic Alchemy Inc, Deep Fission Inc, Last Energy Inc, Natura Resources LLC, Oklo Inc (selected for two projects), Radiant Industries Inc, Terrestrial Energy Inc, and Valar Atomics Inc.

CEO Matt Loszak made the commercial scale of Aalo's ambitions plain at the unveiling, drawing a contrast with smaller experimental units already in the field: "We've seen some nuclear reactors producing 100 kilowatts, 500 kilowatts, or a megawatt. What we're doing is ten to 100 times more powerful than those other reactors." Aalo also recently signed an agreement with Idaho Falls Power to provide 70 megawatts of nuclear power to the grid, and the company expects the facility to be fully operational next year once a co-located data center for nuclear and artificial intelligence projects is complete.

Aalo's CTO Yasir Arafat has said the company plans to bring a new, full-scale, 1-million-square-foot factory online by 2028 named the GigaWatt Factory. At the ceremony, Aalo hung a plaque inside the facility to mark the occasion. "The first light of the second atomic age is dawning," the company wrote. "Criticality Awaits.