A backup safety system at a Duke Energy Corp. nuclear plant in South Carolina nuclear plant wouldn't have worked if it had been needed, federal regulators said Wednesday, a finding that means increased oversight and inspection from the Nuclear Regulatory Commission.
This summer, engineers at Duke Energy's Oconee Nuclear Station, about 30 miles west of Greenville, determined that pressurized heater breakers used in the station's standby shutdown facility were not working properly. That facility is designed to shut down the plant in case something like a tornado or flood means that normal shutdown modes can't be used.
NRC officials inspected the plant, notifying Duke in September of problems with the heater breakers and meeting with company officials last month to discuss safety issues. On Wednesday, the agency said the issue merited a "yellow" rating, its second-most severe safety level.
The pressurized heater breakers that caused the problems were swiftly replaced by fuses and fuse boxes that can withstand higher heat and temperatures, Oconee officials have said. The changes were made in all three of Oconee's units.
The NRC said a second violation involving the replacement breakers was classified as "green," or of very low safety significance.
"The breakers were subsequently replaced with fuses that testing shows remain operable," NRC Region II Administrator Victor McCree said. "Throughout this process, Oconee continued to operate safely. However, this represents a significant problem involving a key safety system and warrants increased NRC inspection and oversight."
Oconee spokeswoman Sandra Magee says the problem was fixed promptly, and Duke is not appealing the findings.
"We've taken care of that," Magee said. "They are good to go."
Magee pointed out that the system is a backup that is needed only if the plant's other shutdown modes can't be used.
"We take their assessment of plant performance very seriously," Magee said. "This facility has never been needed in the 38 years of Oconee's operation."
NRC officials are coming back to Oconee in January for a follow-up inspection. The public was never in danger because the system wasn't needed, the NRC said.