Federal investigators will take a closer look at last Thursday's electrical power loss at the Rancho Seco Nuclear Generating Plant and the spill of about 450 gallons of radioactive water, it was announced Tuesday.
The Nuclear Regulatory Commission said it has "upgraded" its probe and formed an incident investigation team to analyze the episode.
"The incident is complex and has potentially significant implications for other nuclear power plants," commission spokesman Greg Cook said.
A preliminary inspection showed that the plant, 25 miles southeast of Sacramento, was operating at about 70% when electrical power to the facility's integrated control system was lost.
"Operators had difficulty controlling the water supply to the plant's steam generators, leading to an excessively rapid cool-down of the reactor pressure vessel," a commission statement said.
"Also, while stabilizing the plant, a pump was damaged, resulting in a spill of about 450 gallons of radioactive water within the plant's auxiliary building."
Officials said some of the water escaped from the building as steam but it was no health danger.