The quiet revolution in American energy just cleared a major technical hurdle.
At Idaho National Laboratory, Antares Nuclear’s Mark-0 microreactor achieved zero-power criticality under the Department of Energy (DOE) Reactor Pilot Program (RPP), becoming the first advanced reactor to meet the ambitious July 4, 2026, deadline set by President Trump’s 2025 executive order to accelerate next-generation nuclear deployment.
The U.S. energy secretary called the development “one of the most significant achievements in nuclear energy in forty years.”
The Department of Energy said the Mark-Zero reactor design by Antares Nuclear, hosted at Idaho National Laboratory, achieved criticality. That means the team started a self-sustaining chain reaction of nuclear fission, the fundamental process for operating a reactor.
The Department of Energy said it is the first time a privately developed, non-light-water reactor has gone critical in four decades, and that it serves as a blueprint for other advanced reactors supported by the Trump administration.
State leaders praised the accomplishment. Sen. Jim Risch posted on social media that Idaho is “leading the charge” to a new era of advanced reactors.
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