The federal Nuclear Regulatory Commission announced Wednesday that it had downgraded the Pilgrim Nuclear Power Station’s safety rating after repeated unplanned shutdowns at the Plymouth facility and recurring problems with the plant’s safety relief valves.
The plant is now one of just three nuclear power reactors nationwide ranked in the next-to-lowest performance category, officials said. There are no plants in the lowest category.
“They are one step removed from the column where they would be at risk of being shut down by the NRC,” said NRC spokesman Neil Sheehan.
Pilgrim will now be subject to more stringent oversight by regulators, who will conduct an inspection to determine what problems — equipment failures, procedural trouble, or human error — led to the shutdowns in 2013 and 2015.
“Pilgrim is going to receive scrutiny at the highest levels,” said Sheehan. Despite the downgrade, he said, regulators do not believe there is a pressing safety risk associated with operating the plant. “If we did, we’d intervene. But we do believe there are enough problems that need addressing that this level of attention was warranted.”
Attorney General Maura Healey called the downgrade “disturbing” and said her primary concern is for the safety and well-being of the people living near the plant, which is owned and operated by Entergy Corp.
“Entergy must act swiftly and decisively to correct these issues and restore the public’s trust in its ability to safely operate this plant,” she said in a statement.
The 680-megawatt Pilgrim plant opened in 1972. In 2012, its operating license was extended to 2032.
Regulators will increase the frequency of inspections at Pilgrim, and Entergy will be required to present its performance improvement plan to regulators at a public meeting.
“Over the coming days Entergy will review the details of the NRC’s decision to consider what actions we need to take to enable Pilgrim Station to return to normal NRC oversight,” Bill Mohl, president of Entergy Wholesale Commodities, said in a statement.
Mohl said that the plant has previously addressed the safety relief valve issue and the plant is operating safely.
The plant has four safety relief valves, Sheehan said, which alleviate pressure and facilitate the cooling of the reactor. If the reactor cannot be sufficiently cooled, the fuel can begin to melt, which can lead to a radiation leak, though Pilgrim has many redundant systems that would kick in if a valve stopped working, said a spokeswoman.
“There are backups to backups,” said Pilgrim spokeswoman Lauren Burmin an e-mail.
All US nuclear power plants are equipped with containment structures to help prevent the release of radioactive material to the environment in the event of an accident, said Sheehan.
In February 2013, said Sheehan, one of the valves at Pilgrim failed to open during a cooldown, though the station was not cited at the time. The plant’s safety rating was downgraded in 2014 after a series of unplanned shutdowns in late 2013.
The problem with the safety valves should have been fully addressed in 2013, said Sheehan, but on Jan. 27 of this year, during a shutdown amid a major snowstorm, another safety relief valve failed to open.
“They had an opportunity in 2013 to identify the problem, and they failed to do so,” said Sheehan. The plant has since replaced all four valves, Sheehan said, but the repeated failures “point to some programmatic and cultural issues that we believe deserve a closer look.”
Burm said in an e-mail that the company recognizes the need to strengthen its corrective action program.
“We work hard every day to find and fix problems in a timely manner,” said Burm.
Governor Charlie Baker, who recently toured Pilgrim, said Wednesday that he was confident in the plant.
“I do believe it’s safe, yeah,” said Baker, the State House News Service said. “I certainly view the issues that have been raised by this most recent report [as] something we need to pay attention to and be careful and thoughtful about, but the NRC is the most knowledgeable enterprise involved in this oversight activity. We’re going to let them lead this one.”
The downgrade drew calls for the NRC to continue its aggressive oversight of the plant until Entergy can prove that it has dedicated the proper resources and training to the safe operation of the plant.
“For decades, I have raised concerns about Pilgrim’s operations, security preparedness, the safety of the surrounding communities in the event of a nuclear accident, and the willingness of Entergy to dedicate sufficient resources to run the reactor safely,” US Senator Edward J. Markey said in a statement. “Pilgrim has had longstanding and repetitive safety problems and unplanned shutdowns that require this increased level of NRC oversight, especially since it is the same design as the reactors that melted down during the Fukushima nuclear disaster.”
Markey said that Entergy should be required to pay for the distribution of potassium iodide, an anti-radiation drug that can prevent thyroid cancer caused by radiation released during a reactor meltdown, to any Massachusetts community that requests it.
Mary Lampert, director of Pilgrim Watch, a group that has long sought to close the plant, said trouble has been brewing at Pilgrim for years.
“This is an old reactor, and like old people such as myself, it requires a lot of money and maintenance,” said Lampert. “Entergy, because it is not able to effectively compete with natural gas and wind, is not making the money that it panned to, is not spending the money for maintenance.”
Lampert, who can see Pilgrim from her home in Duxbury, said she feared an accident at the plant.
“You recognize accidents can and do happen,” she said. “That’s something you don’t like to think about, because you’re here.”
Evan Allen can be reached at email@example.com. Follow her on Twitter @evanmallen.