Pilgrim Nuclear Power Station in Plymouth returned to service Wednesday following its seventh outage or other unexpected problem in two years, prompting critics to question whether there are larger issues at the plant.

The plant was shut down Monday after workers found a leak in a safety valve; earlier in January Pilgrim went offline for six days when recirculation pumps used to adjust power levels stopped working.

Despite the outages, federal regulators said there have not been enough incidents to warrant additional oversight of Pilgrim.

“We look back at the last 7,000 hours of online operation to see if they have more than three” shutdowns, said Nuclear Regulatory Commission spokesman Neil Sheehan. “As of now, the latest shutdowns would not appear to put them over the performance indicator.”


Of the seven incidents in the past two years, five were unexpected outages and two were unplanned changes in power levels at the plant, according to the commission.

Another incident would likely trigger a tougher federal review, said Dave Lochbaum, director of the Nuclear Safety Project at the Union of Concerned Scientists.

“They’ll send more inspectors to the site [to find out] is there a common thread? Did they just have a streak of bad luck? Or is there some programmatic problem that manifested itself in these recent events?” Lochbaum said. “Right now they just look coincidental.”

None of the recent outages endangered the public, according to reports submitted to the NRC by Pilgrim’s owner, Entergy Corp. of Louisiana.

But regulatory data do show that the facility — which recently had its operating license renewed for another 20 years — has exceeded the industry average for sudden shutdowns.

Pilgrim was shut down unexpectedly in May, when a piece of equipment called a vacuum condenser degraded while plant operators were reducing power to the reactor in preparation for other work.


There were also two unplanned outages in 2011: one for a leaky valve similar to the one that malfunctioned this week; and another that led regulators to inspect the facility and prompted Entergy to implement better training and operating procedures.

Entergy spokeswoman Carol Wightman said the company has spent millions upgrading Pilgrim’s equipment and the plant’s operators follow a “robust” preventative maintenance program to limit problems, but they can still crop up.

“If we have a valve that needs to be fixed and we have to shut down the plant to fix that, that’s what we do,” she said. “I mean, safety is our highest priority, [and] some of these valves and pipes are in containment and can’t be worked on unless the plant is offline.”

In Plymouth, Town Manager Melissa Arrighi said she has an upcoming meeting with Entergy officials and the recent shutdowns may come up. On Tuesday, Arrighi said Plymouth selectmen spent part of their weekly meeting discussing Pilgrim and whether to implement a communitywide drill of the town’s evacuation plan.

“Anytime we sit at the table with Entergy . . . we talk about plant safety. The reality is this is an aging facility and it’s a nuclear power plant,” Arrighi said. “We rely pretty heavily on the NRC. Is that the best answer? I’m not sure it is.”

Erin Ailworth can be reached at eailworth@globe.com. Follow her on Twitter @ailworth.