SouthernWorldwide.com – Antares Nuclear, Inc. announced on Thursday that its Mark-0 microreactor has successfully achieved criticality at the Idaho National Laboratory, marking a significant nuclear milestone.
This achievement makes Antares the first private company to bring an advanced reactor to criticality under a pilot program established by the U.S. Department of Energy. This program was initiated following President Donald Trump’s 2025 executive order, which aimed to accelerate nuclear development.
The Torrance, California-based company confirmed that the reactor reached initial criticality under authorization from the Department of Energy. This signifies a crucial step in the development and deployment of advanced nuclear technologies.
“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,” stated Antares CEO Jordan Bramble.
Bramble further elaborated on their ambitious timeline: “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.”
Reactor criticality is the point at which a nuclear reactor can sustain a self-sustaining nuclear chain reaction. This is a fundamental milestone in the process of reactor development and operation.
Antares indicated that this demonstration successfully validated key reactor physics parameters. It also provided valuable testing data and information on control system performance, which will be instrumental for future reactor designs.
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The Department of Energy officially confirmed the achievement on Thursday. They highlighted it as the first privately developed non-light-water reactor to reach criticality in the United States in over four decades.
Energy Secretary Chris Wright issued a statement, calling the event “a historic moment for American nuclear energy.” He added, “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.”
This significant milestone arrives just over a year after President Trump signed four executive orders. These orders were designed to expedite reactor testing, boost domestic nuclear fuel production, and streamline regulatory pathways for advanced nuclear technologies.
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One of these executive orders, Executive Order 14301, specifically directed the Department of Energy to create a pilot program. The program’s objective is to accelerate the testing and demonstration of advanced reactor designs.
The administration had set a target date of July 4, 2026, for achieving criticality for advanced reactor concepts. Antares’ success predates this target, demonstrating remarkable efficiency.
“The President and DOE set an ambitious timeline for reactor testing, and we met that challenge,” Bramble stated. He expressed gratitude to their partners, including 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,” Bramble emphasized, underscoring the collaborative nature of the project.
Antares confirmed that the criticality demonstration was a collaborative effort. Key partners included the Department of Energy, Idaho National Laboratory, and BWX Technologies. The U.S. Army participated as a prospective end-user of the technology.
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The Mark-0 reactor utilized TRISO fuel, which was fabricated by BWXT. The fuel technology itself benefited from development through Project Pele, a Defense Department initiative aimed at creating transportable microreactors for military applications.
Officials from the Department of Energy pointed to this achievement as a strong indicator of the Reactor Pilot Program’s potential. They believe it showcases the program’s effectiveness in moving advanced reactor concepts forward.
Assistant Secretary of Nuclear Energy Ted Garrish commented, “The skeptics didn’t believe President Trump’s Reactor Pilot Program could achieve criticality in less than a year.” He added, “Today, we celebrate the first of the pilot projects to reach criticality and the people who rolled up their sleeves to shape the future of nuclear energy in the United States.”
During the demonstration, engineers gathered critical insights into reactor physics, control systems, and supply chain performance. This data will be crucial for supporting the development of future reactors and obtaining eventual commercial licenses.
“We went from concept to a critical reactor, safely, in less than 12 months. That doesn’t happen by accident. The team treated the schedule as non-negotiable,” Bramble said.
He stressed the importance of efficient and iterative testing for the success of the American nuclear renaissance. “For the American nuclear renaissance to succeed, we need efficient, iterative reactor testing, not a decade per design,” Bramble concluded.
Antares anticipates commencing electricity production from the same facility in 2027. The company remains on track to deploy electricity-generating microreactors to U.S. military installations by 2028, fulfilling its commitment to powering critical infrastructure.
