One of three reactors at the Palo Verde Nuclear Generating Station outside Phoenix shut down automatically after an electrical short circuit cut power to two of the unit's four coolant pumps.
Arizona Public Service Co. spokesman Jim McDonald says the short happened in a high voltage electrical panel connecting a transformer to reactor equipment late Sunday morning.
An APS report filed with the Nuclear Regulatory Commission says all reactor shutdown systems operated normally. The reactor was running at 100 percent power at the time of the incident.
McDonald said Monday that crews will inspect the damaged power bus and related ducting and make necessary repairs before the reactor is restarted. He gave no estimate for how long that might take.