DOE Reactor Pilot Program

Built World

As of August 2026: Met its three-reactor criticality goal ahead of schedule and expanded into a longer-running Nuclear Energy Launch Pad program

On June 4, 2026, Antares Nuclear's Mark-0 reactor at an Idaho desert lab started a self-sustaining nuclear reaction. It was the first privately built non-light-water reactor to do that in the U.S. in more than 40 years, and four rival startups matched the feat within nine weeks.

Updated Aug 8