Antares Receives DOE Documented Safety Analysis Approval for Mark-0 Demonstration Reactor

Milestone places Antares in the final phase before DOE Startup Approval and first criticality

IDAHO FALLS, Idaho--(BUSINESS WIRE)--The advanced nuclear energy company Antares received U.S. Department of Energy (DOE) approval of the Documented Safety Analysis for its Mark-0 reactor under DOE standard 1271.

This approval follows Antares' Preliminary Documented Safety Analysis approval in January 2026. This milestone reflects DOE's acceptance of the final design for the Mark-0 reactor and the safety case supporting it.

Antares now begins the DOE Readiness Review process, the final phase before the DOE approves the startup of our reactor pilot. Antares remains on track to go critical ahead of July 4, 2026.

“We are entering the final innings, and that’s incredibly exciting,” said Jordan Bramble, CEO and founder of Antares. “Getting here was only possible with strong support from our partners at Idaho National Laboratory and BWXT, and leadership at DOE, along with relentless work from the Antares team.”

"We developed this timeline in 2023, and we have hit every milestone since," said Bramble. "This is a clear sign that we are proving our safety basis every step of the way, and I’m proud of the way this team has cleared key checkpoints, on schedule, again and again.”

“The Department of Energy is pleased to see Antares reach this important milestone,” said Rian Bahran, Deputy Assistant Secretary of Energy for Nuclear Reactors. “We remain committed to working with innovative companies like Antares to reach the President’s ambitious goal of ensuring at least three reactors reach criticality before July 4, 2026.”

The Mark-0 demonstration will validate reactor physics, neutronics models, and the instrumentation and control system that will also be used in the Mark-1 electricity-producing reactor planned for 2027. Fuel fabrication for the company’s first reactors has been underway through BWX Technologies since October 2025, using HALEU fuel secured through a DOE allocation.

Following the Mark-0 demonstration, Antares will use the same test facility and fuel batch for its Mark-1 reactor in 2027, advancing toward initial deployments for defense and space customers in 2028.

About Antares

Antares is building compact nuclear microreactors to deliver reliable, rapidly deployable energy where it’s needed most: remote military bases, austere industrial sites, and, one day, deep space and underwater missions. For more information, visit https://antaresindustries.com/.