Antares Mark-0 Microreactor Achieves First Criticality Under DOE Advanced Reactor Pilot Program

Antares Nuclear, Inc. U.S. Department of Energy pilot program established after President Donald Trump's 2025 executive order.

The Torrance, California-based company said the reactor reached initial criticality under DOE authorization, making Antares the first private company to bring an advanced reactor to criticality through the Reactor Pilot Program. Criticality occurs when a reactor achieves a self-sustaining nuclear chain reaction. "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. " The demonstration validated key reactor physics parameters and produced testing data and control system performance information, Antares said.

Engineers gained insight into reactor physics, control systems and supply chain performance during the test. U.S. in more than four decades.

"Today's achievement is a historic moment for American nuclear energy," Energy Secretary Chris Wright said. " The milestone comes just over a year after President Trump signed four executive orders directing the federal government to accelerate reactor testing, expand domestic nuclear fuel production and streamline pathways for advanced nuclear technologies.

The administration set a goal of achieving criticality for advanced reactor concepts by July 4, 2026. "The President and DOE set an ambitious timeline for reactor testing, and we met that challenge," Bramble said. The criticality demonstration was conducted in partnership with the Department of Energy, Idaho National Laboratory and BWX Technologies.