Cooper Nuclear Station will undergo a special inspection to review operator errors that affected a safety-related heat removal system, said officials at the Nuclear Regulatory Commission (NRC).
Nebraska Public Power District operates the plant, located in Brownville, NE, located three miles south of Brownville on the Missouri River.
“This special inspection will help us better understand the circumstances that led to the operator error,” said NRC Region IV Administrator Kriss Kennedy. “We need to assess the potential impact on plant safety and the licensee’s corrective actions to ensure that the cause has been effectively addressed.”
On Feb. 5, workers discovered that a misalignment of valves may have rendered one of the plant’s residual heat removal systems inoperable for several months. Operators also performed maintenance and testing on a second residual heat removal system during the same period. As a result, there may have been a period of approximately 72 hours when both systems were unavailable.
The residual heat removal system would see use to mitigate the effects of a variety of accidents.
The situation stems from scheduled maintenance as part of a refueling outage performed on Oct. 7, said Drew Niehaus, nuclear communications coordinator for the district. Two valves required to be open ended up incorrectly sealed at the time, Niehaus said.
“It was a human performance error,” he said. “They (valves) were put in the correct position. … This was an isolated incident.”
Two NRC inspectors will begin their weeklong inspection March 13. A report on the findings will be publicly available within 45 days of the end of the inspection.