06/06/2026
Idaho is at the Forefront of the Nuclear Renaissance
This week, the U.S. Department of Energy announced that Antares Nuclear’s Mark-0 microreactor successfully achieved criticality at the Idaho National Laboratory. In simple terms, the reactor reached a self-sustaining nuclear chain reaction, one of the most important milestones in reactor development. This marks the first privately developed advanced reactor in the United States to reach this milestone in more than 40 years.
This achievement highlights Idaho’s leadership in nuclear innovation and reinforces INL’s critical role in developing the next generation of reliable, secure, carbon-free energy. As energy demand continues to grow, Idaho remains at the forefront of the nuclear renaissance, helping power America’s future while strengthening our economy, workforce, and national security. ⚛️🇺🇸
Exciting times for Idaho and for America’s nuclear future.
🎉WE HAVE CRITICALITY! 🎉
On June 4, 2026, at around 12:30 MDT, Antares Nuclear’s Mark-0 microreactor achieved initial criticality at Idaho National Laboratory.
It is the first nuclear test reactor to go critical under the U.S. Department of Energy's Reactor Pilot Program. Data gathered from the test will help validate the nuclear fundamentals and instrumentation and control of the company’s advanced reactor design and provide a fast-tracked approach to future commercial licensing activities.
The demonstration was conducted in partnership with DOE and INL, with support from BWX Technologies, Inc. (BWXT) and the U.S. Department of War.
The Reactor Pilot Program was created in June 2025 to reform reactor testing at DOE in response to President Trump’s Executive Order 14301, which set a goal of achieving criticality for at least three test reactors using the DOE authorization process by July 4, 2026.
Congratulations to Antares on reaching this historic milestone!