First private US non-light-water reactor achieves criticality in decades

Antares Nuclear's Mark-0 reactor reached criticality, a first for a US private, non-light-water reactor in over 40 years. The successful DOE-backed test at Idaho National Laboratory validates its design for future commercial deployment.

In a landmark achievement for American energy, Antares Nuclear's Mark-0 advanced reactor has completed its zero-power fueled criticality demonstration at the US Department of Energy's (DOE) Idaho National Laboratory.

The milestone, achieved on Thursday, marks the first time in over four decades that a privately developed, non-light-water reactor has reached criticality in the United States. The demonstration serves as a centrepiece of the DOE's Reactor Pilot Program, an ambitious initiative launched in 2025 to accelerate the testing and deployment of next-generation nuclear technologies.

'A Historic Moment for American Nuclear Energy'

The successful test confirms the safety and operational viability of the Mark-0 design, providing a vital blueprint for future commercial deployments. By reaching this goal ahead of the July 4, 2026, deadline set by US President Donald Trump, the project has validated the efficacy of the government's streamlined regulatory and testing pathway. "Today's achievement is a historic moment for American nuclear energy," said US Energy Secretary Chris Wright. "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."

Catalyst for a New Energy Landscape

The Mark-0 project is more than a one-time test; it is a catalyst for a broader shift in the national energy landscape. The data gathered from this test will directly inform the design and licensing of subsequent commercial reactors, which are anticipated to begin electricity production in 2027. Once fully commercialised, these microreactors are slated for a wide range of applications, including critical infrastructure support, military installation energy resilience, and even future space exploration missions. This success builds momentum for the newly established Nuclear Energy Launch Pad, which is designed to scale such pilot projects into widespread commercial operations.

"DOE's Reactor Pilot Program has served as a transformative catalyst for American nuclear energy," said Jordan Bramble, CEO of Antares Nuclear. "Beyond reactor physics, we've gained a profoundly greater mastery of our regulatory pathway and our supply chain."

A New Era of Innovation

As the 53rd reactor to be built at the Idaho National Laboratory since 1951, the Mark-0 not only honours a storied legacy of American nuclear science but also signals a new era of rapid, private-sector-led innovation in the pursuit of a sustainable and secure energy future. (ANI)

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