Antares Energy’s first‑test reactor hit criticality in a lab run, proving its modular design can achieve a self‑sustaining chain reaction. The Mark 0 unit lacks the full power‑generation loop, focusing instead on validating models and gathering safety data. Successful criticality marks a milestone for the company’s compact nuclear concept in the United States for future deployments.

The reactor uses TRISO fuel particles wrapped in graphite to contain fission products, reducing the chance of a core melt. Neutrons that escape are slowed by the graphite sheath, limiting the creation of unstable isotopes. Sodium coolant carries heat to a heat exchanger that drives a turbine via a closed Brayton cycle for energy generation today.

Antares keeps the heat‑transfer loop separate from the core, using pressurized nitrogen to drive the turbine and isolate radioactive material. The Mark 0 test also feeds data into licensing dossiers, while plans to run the full system, including power output, target next year. Company partners with Department of Defense’s Project Pele and NASA for reactor in the.

Criticality in a non‑power loop signals that Antares’ compact design can achieve a self‑sustaining reaction safely, a key hurdle for mobile or remote power. The data gathered will support licensing and demonstrate the viability of sodium‑cooled, TRISO‑based reactors for defense and space missions. The test confirms the concept’s technical feasibility for future energy solutions today.