BROWNVILLE, Neb. (AP) — Federal inspectors plan to review how well a Nebraska utility handled a water service safety problem blamed on a silt buildup from the Missouri River, which overwhelmed or broke through levees last spring.
The Cooper Nuclear Station near Brownville was operating on full power Dec. 6 when employees detected that water wasn’t flowing through a pipe connected to one of the plant’s two safety generators, the Nuclear Regulatory Commission said in a news release Thursday. The generators weren’t running because they are designed to kick in and provide power for the plant’s cooling systems only when all five lines that power the plant are knocked out. If needed, the other generator was available, the NRC said.
The plant generated power throughout the problem. The plant owner and operator, the Nebraska Public Power District, soon determined that silt had built up and blocked the pipe outfall, the NRC said. The district had the silt removed within a week.
The plant’s water intake site was normal and there had been no indication of any problem at the discharge site, said power district spokesman Mark Becker.
“We’ve never had that happen before,” Becker said. Officials were still trying to determine where the silt came from because the river water taken in for cooling is heavily filtered before it begins its work inside the plant, Becker said. No issues have been found in a check of water systems inside the plant, he said.
The Missouri River is already known as “The Big Muddy” — a nickname made even more apt by the flooding, Becker said.
“Just think how much flooding there was and how much runoff there was from fields,” he said.
The Missouri remained high since spring flooding caused by heavy rain and snowmelt flowing into the river and its tributaries was near record levels this year. The Missouri River gauge at Brownville was at or above flood stage for 272 days, the National Weather Service said.
Floodwater threatened the plant in March, but it never stopped generating power, Becker said at the time. The rising river water stopped 4 inches (10 centimeters) short of the level at which the reactor had to be shut down as a safety precaution.