Officials at a Southern California nuclear plant searched for the cause of a non-radioactive ammonia leak that triggered an unusual emergency alert and precautionary evacuation of some workers before it was contained.
Officials stressed there was never any danger to the public.
Workers stopped the leak by 5 p.m. Tuesday, about two hours after it was detected in a storage tank in the water purification system of San Onofre Nuclear Generating Station's Unit 3, said Todd Adler, the plant's engineering manager.
The emergency alert was required because fumes could prevent access to certain areas of the plant, Adler told reporters at a media information center in Irvine, Calif.
The alert, the second lowest of four federal classifications for emergencies at commercial nuclear power plants, was canceled at 6:07 p.m. and evacuated workers were allowed to return.
"It's a chemical spill that could happen at any industrial facility," Adler said.
The leak was in the non-nuclear section of the plant, which is operated by Southern California Edison. No radioactive material was released, no injuries were reported and there was no danger to the public, the company said.
Approximately 25 gallons of leaked ammonia were collected in a basin underneath the tank that was designed for that purpose, Edison spokeswoman Lauren Bartlett said.
Exposure to high levels of ammonia can cause irritation, serious burns, lung damage, and even death.
It is used at the plant to treat water that is turned into steam, which runs the turbines that produce electricity. The treated water also is used to remove heat from the reactor's cooling system.
The leak did not affect electricity production at the plant, and other units remained fully operational, Adler said.
The plant is located about 45 miles north of San Diego, just south of San Clemente, and is jointly owned by Edison, San Diego Gas and Electric and the city of Riverside.
While not dangerous for the public or plant workers, an emergency alert at the power plant is an unusual occurrence.
"This is not normal," Edison spokesman Chris Abel said. "The last time we had one (alert) declared was May 1999, because of a suspected pipe bomb on the freeway."
In July, an "unusual event" was declared at the nuclear plant when one of several redundant security systems used to monitor the grounds stopped working, utility officials said. The system was restored within 45 minutes.