"IRVINE, Calif. -- A non-radioactive ammonia leak at a Southern California nuclear plant prompted an emergency alert and precautionary evacuation of nearby workers before it was contained Tuesday, authorities said.

Workers stopped the leak by 5 p.m., about two hours after it was detected in a storage tank in the water purification system of Unit 3 at San Onofre Nuclear Generating Station, 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 was canceled at 6:07 p.m. and evacuated workers were allowed to return."
 
Amy Taxin reports for the Associated Press October 1, 2011. [2]

SEE ALSO:

"Emergency Alert Called Off at San Onofre Nuclear Plant" (Los Angeles Times)
[3]
"San Onofre Power Plant Emergency: Level 3 Alert" (Huffington Post) [4]