Antares reaches reactor criticality under Trump pilot program, marking major nuclear milestone

"Hitting our commitments is everything to us. Nuclear in America has been defined for too long by delays, by companies that said they would and then didn't," Antares CEO Jordan Bramble said. "We said criticality in 2026, electricity production in 2027, and power to the warfighter in 2028. Today is the first of those commitments delivered on the schedule we set."

Criticality occurs when a reactor achieves a self-sustaining nuclear chain reaction, a major milestone in reactor development. Antares said the demonstration validated key reactor physics parameters and produced testing data and control system performance information that will support future reactor development.

The Department of Energy confirmed the achievement Thursday, describing it as the first privately developed non-light-water reactor to reach criticality in the U.S. in more than four decades.

One of those orders, Executive Order 14301, directed the Department of Energy to establish a pilot program designed to speed testing and demonstration of advanced reactor designs. The administration set a goal of achieving criticality for advanced reactor concepts by July 4, 2026.

Antares said the criticality demonstration was conducted in partnership with the Department of Energy, Idaho National Laboratory and BWX Technologies, while the U.S. Army participated as a future end user of the technology.

DOE officials said the achievement demonstrates the potential of the Reactor Pilot Program.

The company said engineers gained critical insight into reactor physics, control systems and supply chain performance during the demonstration. The data will be used to support future reactor development and eventual commercial licensing.

Antares said it expects to begin producing electricity from the same facility in 2027 and remains on track to deploy electricity-generating microreactors to U.S. military installations by 2028.