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    At Pilgrim, a probe into whether backup generators were offline

    The Pilgrim Nuclear Power Plant as seen from the sea.
    Keith Bedford/Globe Staff
    The Pilgrim Nuclear Power Plant as seen from the sea .

    Federal nuclear safety regulators are investigating whether emergency diesel generators at Pilgrim Nuclear Power Station in Plymouth were offline for more than 24 hours in April, in violation of the plant’s license, a Nuclear Regulatory Commission spokeswoman said.

    The incident may cause renewed concern among critics of the embattled plant — already slated for shutdown in 2019 and under increased NRC supervision — who worry the aging facility is no longer safe.

    On April 10, around 7 p.m., workers at Pilgrim removed one of the plant’s two emergency generators for scheduled maintenance, according to an incident report Pilgrim’s owner-operator, Energy, filed with the NRC on June 9. Around 9:30 p.m. on April 11, more than 25 hours later, workers discovered that the other backup generator was leaking water. They removed it from service soon after and restored it the next day.


    The question federal investigators need to answer is when the leaky generator became inoperable.

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    “They’re looking at what actually happened to see if there might have been other opportunities” to catch the second generator’s problems, said David Lochbaum, director of the Nuclear Safety Project for the Union of Concerned Scientists, who brought the timeline to the NRC’s attention. “Some plants are very vigilant, and in other plants, workers are only doing what they’re told to do, not more. We’re basically trying to answer,who knew what, when?”

    The generators exist in case primary and secondary power sources fail. According to Lochbaum, Pilgrim deploys its emergency generators more than most other nuclear plants — roughly once every two years — due to the area’s vulnerability to winter storms.

    Patrick O’Brian, a spokesman for Entergy, Pilgrim’s owner-operator, said in a statement that proper procedure had been followed, and that there was no impact on public health or worker safety. He confirmed that the emergency generators were deployed in 2013 and 2015.

    The NRC will conduct an investigation and, if it finds a breach of regulations, will determine the appropriate sanction, said NRC spokeswoman Diane Screnci. That sanction would take into account the fact that Pilgrim is already under enhanced supervision, she said.


    The findings of the investigation will likely be released at the end of the summer, she said.

    Vivian Wang can be reached at Follow her on Twitter @vwang3.