A turkey flew into an overhead powerline and tripped a circuit breaker at the Y-12 National Security Complex in Oak Ridge, Tenn., last month, blacking out buildings on the west side of the site and very briefly affected critical safety systems in facilities that produce key nuclear-weapon components, federal officials said this week.

The outage lasted approximately 1 hour and 45 minutes,” a spokesperson for Consolidated Nuclear Security (CNS), the site prime, wrote in an email Tuesday afternoon. “All nuclear facilities have back-up generators, and the back-up generators operated as intended.”

Late in the afternoon on March 18, “an unplanned power outage affected several facilities at Y-12, including Buildings 9212, 9215, 9204-2E, and the Highly Enriched Uranium Materials Facility,” the Defense Nuclear Facility Safety Board (DNFSB) wrote in a recent report. CNS “investigated the issue and found that a turkey had caused a breaker to trip.”

The independent federal watchdog for DoE nuclear sites besides naval nuclear sites posted its report online between Friday and Monday.

Building 9212 is Y-12’s uranium processing hub. There, the National Nuclear Security Administration (NNSA) produces canned subassemblies that are the secondary stages of modern thermonuclear weapons. 

In Buildings 9212 and 9215, the turkey-related outage caused criticality accident alarm systems and emergency notification systems to go offline, the CNS spokesperson said. Building 9204-2E also briefly lost its emergency notification system. Backup power kicked in within seconds, though it took a little longer to restore the criticality accident alarm systems to their normal state.

Nobody was hurt as a result of the blackout, the CNS spokesperson said, though “[a]s a precaution, fissile activities in affected buildings were suspended until the Criticality Accident Alarm System (CAAS) was fully functional, within 45 minutes after power was fully restored.