A California-based nuclear technology company says it has cleared a major hurdle in its effort to bring next-generation reactors online, marking what federal officials described as a significant moment for the U.S. nuclear industry.
According to Fox News, Antares Nuclear announced Thursday that its Mark-0 microreactor achieved criticality at Idaho National Laboratory, becoming the first advanced reactor to reach that stage through a Department of Energy pilot initiative.
Criticality is the point at which a reactor sustains its own nuclear chain reaction, a key benchmark in reactor testing and development.
The company said the achievement validates important reactor physics calculations and provides data on system performance that will be used to support future designs.
Antares CEO Jordan Bramble emphasized that the company had met a timeline it publicly committed to.
“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,” 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.”
The Department of Energy confirmed the reactor’s achievement, describing it as the first privately developed non-light-water reactor in the United States to reach criticality in more than 40 years.
The milestone follows a series of executive orders signed by President Donald Trump last year that directed federal agencies to accelerate testing of advanced reactors, increase domestic nuclear fuel production, and simplify development pathways for emerging nuclear technologies.
One of those directives established the Reactor Pilot Program, which was designed to test and demonstrate advanced reactor concepts rapidly.
The administration set a target of achieving criticality for such projects by July 4, 2026.
According to Antares, the reactor demonstration was conducted in partnership with the Department of Energy, Idaho National Laboratory, and BWX Technologies. The U.S. Army also participated as a future user of the technology.
The reactor utilized TRISO fuel produced by BWXT and incorporated fuel technology developed through Project Pele, a Defense Department program focused on transportable microreactors for military use.
The company said it expects the facility to begin generating electricity in 2027 and remains on schedule to deploy power-producing microreactors at U.S. military installations by 2028.
