For the third time in 18 months, inspectors found missing flood seals at the Vermont Yankee nuclear plant, a problem that could hinder the plant’s ability to operate electrical safety systems.
Inspecting for flood seals has been a Nuclear Regulatory Commission (NRC) priority since the nuclear disaster in Fukushima, when flood water from a tsunami inundated several nuclear plants similar in design to Vermont Yankee.
Inspectors found the most recent issue Nov. 6 during an annual inspection of the manholes at the Vernon plant, said NRC spokesman Neil Sheehan.
In that instance, Entergy Nuclear failed to correct missing and faulty flood seals found last spring in underground pipes, Sheehan said.
He said Entergy Nuclear hired a contractor to replace the missing seals, but the contractor had failed to do the job. He said Entergy is responsible for the work of the contractor.
If water is able to leak into underground conduit or pipes carrying electrical systems, Vermont Yankee’s safety could end up compromised, according to the licensee event report posted by the NRC.
In the most recent case, a missing conduit flood seal between an outside manhole and the west “switchgear room compromised the flooding design of both the east and west switchgear rooms,” the NRC reported.
Entergy Nuclear spokesman Jim Sinclair said the problems had prompted Entergy to review its inspection program.
“We are reviewing the circumstances that resulted in the condition we found and will be doing an extensive review to identify the root cause and any enhancements we need to make to our inspection program,” Sinclair said Friday.
He said after the inspection turned up the problem, they installed a new seal.
“We are also re-inspecting all similar manholes to verify that all necessary seals are in place,” he said.
Sheehan said that in March, a manhole identified as “S2” had problems with three conduit seals. He said that two had incorrect screw plug seals and one had a missing seal. One of the two screw plugs ended up dislodged, he said.
“A work order was generated at that time to correct the deficiencies and the company believed the work order was completed and that all three conduits were corrected by installing a poured sealant,” Sheehan said.
But he said during the Nov. 6 annual manhole inspection, “workers again found problems in manhole S2.”
In August, Entergy said Vermont Yankee will cease power production after its current fuel cycle and will begin decommissioning in the fourth quarter of 2014.