Note: Single-source report; awaiting corroboration.
The United States has made significant progress in advanced nuclear energy, achieving criticality in four new advanced test reactors by July 4, 2026, surpassing the target set in President Trump’s May 2025 executive order. This milestone marks a step forward for next-generation nuclear technology designed to meet the nation’s growing energy needs with affordable, reliable electricity for the future.
In June 2025, the Energy Department launched the Reactor Pilot Program to accelerate advanced reactor deployment, aiming for at least three reactors to reach criticality by America’s 250th birthday. By August 2025, the department announced 11 initial selections for advanced reactor projects from 10 companies, including Aalo Atomics, Antares Nuclear, Atomic Alchemy, Deep Fission, Last Energy, Oklo, Natura Resources, Radiant Industries, Terrestrial Energy, and Valar Atomics.
Four of these reactor projects are hosted at Idaho National Laboratory (INL), featuring the Radiant (KDU), Antares (Mark-0), Aalo (Aalo-X), and Oklo (Aurora) designs. Notably, Antares Nuclear’s Mark-0 reactor reached criticality through a zero-power fueled test demonstration at INL on June 4, 2026. This event marked the first time in over four decades that a new privately developed non-light-water nuclear reactor achieved criticality in the U.S., confirming safe operation and paving the way for future reactors to generate electricity.