Aalo Atomics, the US company building fully modular nuclear plants to power AI data centres, has demonstrated criticality for its demonstration Aalo-X Critical Test Reactor at Idaho National Laboratory (INL), meeting president Donald Trump’s goal of having at least three advanced reactors achieve the landmark by 4 July 2026.

Aalo said criticality, which marks the first self-sustaining chain reaction within a nuclear fission reactor, was achieved in the early morning hours of 4 July.

Achieving criticality by 4 July was in line with targets under the US Department of Energy’s (DOE) nuclear reactor pilot programme.

The Aalo-X, a 10-MW sodium-cooled experimental reactor, is designed to validate its technology at full scale ahead of future commercial deployment.