Overview
- Antares Nuclear said its Mark‑0 microreactor achieved initial zero‑power criticality on June 4, 2026, a DOE confirmation that the reactor sustained a self‑maintaining chain reaction at negligible power.
- The test was run at Idaho National Laboratory under the Department of Energy’s Reactor Pilot Program created after President Trump’s 2025 executive orders and yielded reactor‑physics and control‑system data rather than electricity.
- Antares used TRISO fuel made by BWXT that builds on Department of Defense Project Pele work, and the company says it plans sustained electricity tests in 2027 and potential military deployments in 2028.
- Key hurdles remain: commercial licensing through the Nuclear Regulatory Commission and scaling reliable HALEU/TRISO fuel production beyond government stocks are still unresolved and will determine commercial rollout timelines.
- Industry and U.S. officials cast the milestone as a restart of advanced‑reactor development with export interest from markets like India, but broader commercialization depends on follow‑on tests, regulatory approvals, and steady fuel supply.