A special inspection is underway at Duke Energy’s Oconee nuclear power plant to assess the degradation of power cables on start-up transformers for two of the plant’s three units, regulators said.
The plant, located near Seneca, SC, is about 30 miles west of Greenville, SC.
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A plant operator making routine inspections on Dec. 7 discovered a disconnected cable to the Unit 3 start-up transformer.
Upon further inspection, it officials determined other cables linked to the Unit 1 start-up transformer were in a degraded condition. Workers repaired all of the cables and the transformers are available for use if needed.
“There was not an event in which the start-up transformers were needed, but they play a very important role in some circumstances by providing electrical power to plant safety equipment,” said Leonard Wert, acting Nuclear Regulatory Commission (NRC) Region II administrator. “We felt a special inspection was warranted to gather more information about Duke’s response and also determine if there are generic issues that may apply to other plants.”
The on-site inspectors for the special inspection are the senior resident inspector from the Oconee plant and an inspector from the NRC’s Region II office in Atlanta.
Another NRC expert from Atlanta will not travel to the site, but will assist in reviewing the data gathered. The team’s work will include a review of the circumstances surrounding the degradation and failure of the cables and the utility’s actions after it identified the degraded conditions.
It will also develop a timeline on when the cables suffered damage and or failed, and review Duke’s testing and maintenance practices.
The on-site portion of the inspection will take several days. A report documenting the results should be available within 45 days of the completion of the inspection.