Pilgrim nuclear power plant in Plymouth, MA, should have prevented a valve failure that led to a white finding after last January’s storm-induced shutdown, officials said.
A report released by the Nuclear Regulatory Commission (NRC) earned the plant one preliminary “white” finding, which designates an event of low to moderate safety concern.
The NRC ratings of incidents go from green, indicating the lowest safety significance, up to white, then orange and red. The inspection team’s findings for the entire Winter Storm Juno event included six green and one white finding.
At the peak of the storm, the plant suffered what is called a LOOP (Loss Of Outside Power), requiring that operators scram (shut down) the reactor. But that was not the source of the white finding.
“One of the complications during the shutdown involved the use of safety relief valves to reduce reactor vessel pressure as part of the reactor cool down process,” the inspection report said. “During attempts to open one of the plant’s safety relief valves, the valve did not open based on observed system response. Plant operators safely completed the cool down using two other of the plant’s four safety relief valves.”
The white finding stemmed from the NRC inspection team’s determination that plant operator Entergy “could have prevented the (safety valve) issue by identifying, evaluating and correcting a condition involving the safety relief valves after a plant shutdown on Feb. 9, 2013.”
When the valves ended up disassembled after the Juno scram, they revealed internal damage to their operating piston and assembly, which made them resistant to opening.
Entergy Senior Communication Specialist Lauren Burm, forewarned of the inspection report’s release, issued the plant’s response before the NRC report reached the media.
The response was Entergy fixed all problems cited by the NRC.
“In the four months since the special inspection team visited the plant following the historic Jan. 27 blizzard,” Burm said, “the issues raised (in the report) by the NRC have all been addressed.”
“Immediately following the storm,” Burm said, “Pilgrim personnel and NRC inspectors moved quickly to thoroughly investigate the equipment issues that had occurred. Since then, our team has worked diligently to correct each one.”
Pilgrim installed four new safety relief valves during the recent refueling outage, Burm said, adding its testing of the valves cited in the inspection discovered “that they may have had defects that caused their performance to degrade over time.”