Antares Nears Microreactor Milestone with Key Federal Safety Approval

IDAHO FALLS, Idaho – January 26, 2026 – Nuclear energy company Antares has secured a critical safety approval from the U.S. Department of Energy (DOE) for its Mark-0 demonstration microreactor, signaling a major step forward in the race to deploy a new generation of compact, portable nuclear power sources.

The DOE's approval of the Preliminary Documented Safety Analysis (PDSA) certifies that the company’s reactor design, facility, and operational plans meet the department's rigorous safety standards. This milestone validates Antares' technology and clears a significant regulatory hurdle, putting the company on a firm path to achieve a controlled, self-sustaining nuclear reaction—known as criticality—in its demonstration unit before July 4, 2026.

The achievement is part of the DOE's ambitious Reactor Pilot Program, an initiative designed to accelerate the development of advanced nuclear technologies by enabling demonstrations at national laboratories. Antares is one of 11 companies selected for the program, which aims to fast-track innovation by providing a pathway to operation under DOE authorization, distinct from the lengthier Nuclear Regulatory Commission (NRC) licensing process required for commercial plants.

"The DOE approval of our PDSA is an important step on our way to criticality and ultimately producing power for defense and space applications," said Jordan Bramble, CEO of Antares, in a statement. "Safety is at the core of everything we do, and we thank the DOE for their continued partnership."

The New Nuclear Frontier: Powering Defense and Space

Antares and its competitors are developing microreactors not for the traditional civilian power grid, but for highly specialized, mission-critical applications where energy resilience is paramount. The primary markets are national security and deep space, sectors where traditional power sources like diesel generators or solar panels have significant limitations.

For the Department of Defense (DoD), microreactors promise to solve a persistent logistical challenge: providing secure, uninterrupted power to remote military bases and forward operating areas. These installations currently rely on vulnerable supply lines for fossil fuels. A compact reactor, capable of operating for years without refueling, could revolutionize military energy independence. Recognizing this potential, the DoD's Defense Innovation Unit (DIU) selected Antares for its Advanced Nuclear Power for Installations program, which aims to deploy a microreactor on a military base by the end of the decade.

Beyond terrestrial defense, these reactors are seen as a key enabling technology for the next era of space exploration. Antares holds active contracts with NASA, reflecting the agency's interest in nuclear fission for powering future lunar or Martian bases, where long nights and harsh conditions render solar power unreliable. The high energy density of nuclear fuel also opens possibilities for advanced propulsion systems that could drastically shorten travel times across the solar system.

A Renaissance in the Making

Antares' progress is a tangible sign of a broader 'nuclear renaissance' underway in the United States, driven by public-private partnerships and a renewed focus on energy security and clean power. The DOE's Reactor Pilot Program is a centerpiece of this strategy, creating a competitive environment to spur rapid innovation. Companies like Westinghouse, X-energy, and Oklo are also developing their own unique microreactor designs, from transportable "nuclear batteries" to high-temperature gas-cooled systems.

The Antares Mark-0 will be tested at the Idaho National Laboratory (INL), a historic hub of American nuclear research. The reactor will be housed in Building 793 of the Materials and Fuels Complex—the same facility that, decades ago, was home to ML-1, the U.S. Army's first mobile nuclear reactor. By repurposing this existing infrastructure, Antares has avoided the time and expense of new construction, a strategy that has been crucial to its accelerated timeline.

"We are excited to turn on our low-power demonstration unit before July 4, and we look forward to learning valuable lessons on fueling, reactor controls, and the physics of our core from our Mark-0 operations," Bramble noted. The data gathered from this initial reactor will be invaluable for the company's next goal: an electricity-producing demonstration scheduled for 2027.

Fueling the Future: The HALEU Supply Chain

A critical component for nearly all advanced reactor designs is High-Assay Low-Enriched Uranium (HALEU), a type of nuclear fuel enriched to a higher level than conventional reactor fuel but still well below weapons-grade. While essential for creating smaller, more efficient reactor cores, a commercial HALEU supply chain does not yet exist on a large scale. This has created a significant bottleneck for the entire industry.

In a key strategic win, Antares has already secured an allocation of HALEU feedstock from the DOE's own limited stockpiles. The fuel is currently being fabricated in collaboration with BWX Technologies, one of the few entities with the capability to handle such materials. This secure fuel supply gives Antares a tangible advantage as it moves toward operating its first reactor.

The development is also a boon for the regional economy. Antares has invested over $40 million in Idaho and is building a growing presence in Idaho Falls, contributing to the state's reputation as the epicenter of advanced nuclear development in the U.S.

This progress has been backed by significant private and public capital. The company has raised over $130 million to date, including a $96 million Series B funding round in late 2025, and holds over $13 million in government contracts. This financial footing, combined with the latest regulatory approval, positions Antares as a leading contender in the high-stakes effort to redefine the future of nuclear power.