COLUMBIA, S.C. - Site operators didn't take all possible precautions to prevent a radioactive water leak that led to shutdown of a South Carolina nuclear reactor, officials with Duke Energy said Thursday, also saying they'd learn from their mistakes.
"Duke Energy agrees that there were apparent violations," Scott Batson, site vice president for the Oconee Nuclear Station, said during a U.S. Nuclear Regulatory Commission meeting in Atlanta.
Engineers and regulators examined the situation last November at the Oconee plant near Seneca, about 30 miles west of Greenville. The shutdown came after engineers detected flaws in the airtight, steel-lined concrete containment building designed to prevent radiation from leaking into the air or ground.
Officials said there was no threat to employees or the public, and the crack was quickly repaired.
Regulators made no decisions public Thursday about the leak's safety significance. In June, the NRC issued a notice to Duke of an "apparent violation" that had a safety significance of "greater than green" - the lowest of the agency's graduated safety system - and ordered the conference to hear from Duke before making a final determination on the severity of the penalty.
Both Duke officials and an independent consulting firm said the risk associated with the leak was very low and was traced to a flaw that was confined to an individual pipe and weld. NRC officials said Duke needed to change the way it looks for these kinds of flaws in the reactor's systems.
Oconee has three reactors, and one of them was already offline for refueling before the shutdown of Unit 1. On Friday, all three reactors were listed as fully operational.
Several weeks before the November incident, Oconee's Unit 3 was shut down when engineers discovered a faulty control valve was causing changes in the flow of water in a different system that generates steam to turn the turbines and create power. That reactor started generating power again three days later and was quickly fully operational.
In October, a Government Accountability Office report found that, since 2000, the Oconee Nuclear Station reported the most safety violations of any nuclear plant in the Southeast, with 163 lower-level violations and 14 higher-level violations.
Lower-level violations pose very low risk, such as improper upkeep of a transformer, while higher-level violations range in significance, like an electrical system that caused a fire.