Officials with Duke Energy said they first detected the leak November 8 and spent the next few days investigating it. The leak is not a threat to plant workers or the public, according to the utility, and it is within the reactor's concrete-and-steel-lined containment unit.
This is the second time in three weeks a problem has brought a reactor at Oconee offline, according to reports.
Duke Energy said the leak releases about one gallon of reactor cooling water every 10 minutes. The reactor was shut down November 11 and repairs began the same day. Duke Energy has not said when repairs will wrap up or when the reactor could be brought back into service.
According to the Government Accountability Office, Oconee has reported 163 low-level safety problems and 14 higher-level violations. These problems range from improper upkeep to an electrical fire.
Oconee was the first of three nuclear stations built by Duke Energy, and its first reactor was commissioned in 1973. It has a power generation capacity of 2.5 GW and uses three Babcock and Wilcox pressurized water reactors.