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

Antares Nuclear, Inc. announced its Mark-0 microreactor reached criticality at Idaho National Laboratory, marking the first advanced reactor milestone under the U.S. Department of Energy’s pilot program. The Torrance, California-based company achieved this under DOE authorization, becoming the first private firm to bring an advanced reactor to criticality through the program. Criticality, a self-sustaining nuclear chain reaction, was reached on schedule, validating key reactor physics and control systems. The DOE confirmed this as the first privately developed non-light-water reactor to reach criticality in the U.S. in over four decades. Energy Secretary Chris Wright called it a historic moment for American nuclear energy. The achievement follows President Donald Trump’s 2025 executive orders accelerating nuclear development, including a goal of criticality for advanced reactors by July 4, 2026. Antares CEO Jordan Bramble highlighted the company’s timeline, with plans for electricity production in 2027 and military deployment by 2028. The Mark-0 reactor uses TRISO fuel fabricated by BWXT, with technology developed through the Defense Department’s Project Pele. The U.S. Army participated as a future end user, emphasizing the reactor’s potential for military applications. The DOE’s Reactor Pilot Program aims to streamline testing and deployment of advanced nuclear technologies.