Operators at Pilgrim Nuclear Power Station have acknowledged a longstanding safety lapse after a review of its fire-protection system this week revealed the plant had failed to comply with a government advisory issued in 1992.
In the latest setback for the Plymouth facility, engineers disclosed Monday they had discovered vulnerabilities in two areas of the plant that required “fire watches,” where trained personnel monitor sections for any evidence of a fire.
The lapse raised the alarming — if remote — possibility that a fire in the control room would compromise the plant’s ability to safely shut down the nuclear reactor.
“It had never been properly addressed, for whatever reason,” said Neil Sheehan, spokesman for the US Nuclear Regulatory Commission, which regulates commercial nuclear power plants. “We’re going to have to assess why it took them until now.”
Sheehan said it was also not clear why NRC inspectors had never noticed the lapse. “That’s something we’re going to have to look at, too,” he said.
The plant’s owner, Entergy Corp., said it has increased monitoring at the plant and is working on engineering changes.
The 1992 advisory, issued after a Washington power plant discovered that valves required for a shutdown could be damaged by a control room fire, was not a formal requirement. One specialist called the problem relatively minor.
But critics said the disclosure spoke to broader, persistent problems at the aging Pilgrim plant, which has come under increasing scrutiny from federal regulators.
“It’s not as if this is the first time safety concerns have been raised,” said Emily Norton, director of the Massachusetts chapter of the Sierra Club, which opposes nuclear energy. “We don’t need any more evidence.”
News of the lapse, first reported by the Cape Cod Times, follows a downgrade in the plant’s safety rating, raising the prospect that the plant may shut down to avoid millions of dollars in required improvements. A series of unplanned shutdowns in recent years, along with substantial safety problems that included recurring issues with relief valves, led to the downgrade.
Sheehan said the plant identified the “potential vulnerability” during a review of its fire protection system. He said the scenario of a fire threatening the plant’s ability to shut down is “highly improbable” but operators should be aware of the threat.
Regulators will review what steps the plant has taken during a November inspection, Sheehan said. It was too early to tell whether the plant would be fined, he said.
“We need to gather more information,” he said.
In a statement, Entergy said the station had established “robust levels of manual and automatic fire detection and suppression in all critical areas.” It added, “Engineering modifications are under development and will be implemented to address the issue.”
The company said the plant will conduct hourly watches “as an additional layer of protection” until the underlying problem is resolved. Workers already are patrolling the areas of concern, including rooms in the reactor building, every four hours.
The company will make phased improvements that will be completed in 2017, a spokeswoman said.
David Lochbaum, director of the Nuclear Safety Project for the Union of Concerned Scientists, said the problem was “relatively minor,” although it should have been noticed earlier. Resolving the issue would be straightforward, he said — “a simple fix compared to the other things on the to-do list.”
In the past two years, regulators have stepped up enforcement of previous advisories, Lochbaum said.
Under the scenario outlined in the advisory, a fire in the plant’s control room could cause short circuits, threatening motor-operated valves needed for a shutdown. The valves could sustain mechanical damage before operators could shift control to an alternative source.
The plant is one of just three nuclear reactors nationwide in the next-to-lowest performance category, officials said. There are no plants in the lowest category.
Critics of the nuclear plant said that even if the lapse was minor, the stakes are too high for virtually any risk.
“Even if there’s a small probability, the consequences when something goes wrong are very large,” said Mary Lampert, director of the group Pilgrim Watch. “And it further undermines the public’s confidence that the reactor is safe.”