A 2025 executive order by President Donald Trump is bearing fruit, according to a recent Antares Nuclear, Inc. announcement.
The company revealed that its Mark-0 microreactor was able to achieve criticality, a state in which a nuclear reaction becomes self-sustaining, at the Idaho National Laboratory. This makes it the “first advanced reactor to reach the milestone under a U.S. Department of Energy pilot program” established by an executive order aimed at nuclear development acceleration, according to Fox News.
Antares Mark-0 has achieved initial criticality! ⚛️ pic.twitter.com/gYQxy0ucrd
— Jordan Bramble (@jordanbramble) June 4, 2026
“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,” said Antares CEO Jordan Bramble. “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 President and DOE set an ambitious timeline for reactor testing, and we met that challenge. I want to thank our partners at the Department of Energy, Idaho National Lab, BWXT, and the U.S. Army. This is what happens when industry and government work together to accomplish big things.”
🎉 WE HAVE CRITICALITY! 🎉
On June 4, 2026, at around 12:30 MDT, @AntaresNuclear’s Mark-0 microreactor achieved initial criticality at @INL.
It is the first nuclear test reactor to go critical under @ENERGY’s Reactor Pilot Program. Congratulations to Antares on reaching this… pic.twitter.com/JS9g9Vsm26
— Office of Nuclear Energy | US Department of Energy (@GovNuclear) June 4, 2026
In a statement, Energy Secretary Chris Wright celebrated the “historic moment for American nuclear energy.”
“Today’s achievement is a historic moment for American nuclear energy. By bringing the first American non-light water privately developed reactor to criticality in more than four decades, Antares has shown what is possible when American innovation is unleashed,” he said.
One of Trump’s first moves after assuming his second term in office was to fire off four executive orders regarding the acceleration of reactor testing, expansion of domestic nuclear fuel production, and efforts to streamline pathways for further nuclear advancement.
“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,” Fox News reported.
Bramble laid out what this massive milestone means for the future of his company.
Look:
I am so proud of the @AntaresNuclear and @INL staff who executed this.
I want to reiterate how this fits into our larger roadmap to mature our technology to its commercial potential. This should be obvious, but the goal of a reactor is to sell electricity to customers. Now that…
— Jordan Bramble (@jordanbramble) June 4, 2026
“I want to reiterate how this fits into our larger roadmap to mature our technology to its commercial potential. This should be obvious, but the goal of a reactor is to sell electricity to customers. Now that Mark-0 is critical, the real work is just beginning. Following our reactor physics experiments, we will execute the next phase of our roadmap — sustained electricity production. We are able to move fast towards this milestone because we’ve already completed over 6 months of full-power thermal testing in an electrical prototype,” he explained. “We will perform version 2.0 of this in 2026. This is an easier, more iterative way to test, because there is no regulatory process, and you can disassemble to examine material effects. All of our iterative testing sets us up to produce electricity for 6+ months. Hundreds of days, not hundreds of hours. We’re able to test for longer and faster because we’ve designed our reactor around a proven, fully qualified fuel spec developed under Project Pele.”
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Sierra Marlee is a millennial whose hunger for the truth in a world of fake news has led her to write. Marlee also contributes to BizPac Review.
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