Nuclear specialists at Diablo Canyon this week to investigate safety switch misalignment

A team of four Nuclear Regulatory Commission specialists are beginning a special inspection today at Diablo Canyon nuclear power plant to determine how two safety switches were misaligned, potentially impairing response in the event of a severe accident.

The inspection is expected to take several days to complete. It will be conducted by Diablo Canyon’s senior resident inspector, two reactor specialists and an emergency preparedness inspector from the agency’s regional office in Arlington, Texas.

The misaligned switches were discovered Oct. 23 during a refueling shutdown. The misalignment would have prevented two cooling water valves from being opened remotely from the reactor’s control room, forcing operators to be dispatched to manually open the valves.

The valves are part of a safety system that collects water from the floor of the containment building for recirculation to cool the reactor in the event of a severe loss-of-coolant accident.

– David Sneed