The U.S. Nuclear Regulatory Commission (NRC) will increase its oversight of the 670-MW Pilgrim nuclear power plant in Massachusetts.
The enforcement action will move the plant into the repetitive degraded cornerstone column, or Column 4, of the NRCâ€™s Action Matrix. The plant transitioned into the degraded cornerstone column, or Column 3, in late 2013 as a result of unplanned shutdowns and unplanned shutdowns with complications the same year. NRC found in December 2014 that plant owner and operator Entergy (NYSE: ETR) did not adequately evaluate the causes of the shutdowns and that some corrective actions had not been completed or were closed out prematurely.
The latest finding was found during a special inspection at the plant following an unplanned shutdown in January 2015 caused by a winter storm that left distribution lines inoperable. One of the complications involved the failure of one of four safety relief valves to open as part of the cool-down process. The plant was already in Column 3 at the time of the shutdown. Inspectors found that Entergy could have prevented the failure if it addressed a previous relief valve issue from a February 2013 storm that also shut down the plant.
The NRC will also determine the need for additional regulatory action and examine the extent of equipment, human performance and procedure quality issues that contributed to or complicated the unplanned shutdowns. All of the safety relief valves were replaced with ones of a different design during a spring refueling maintenance outage. Entergy said during a regulatory conference that two of the valves were fully operational and the other two would have worked at high-pressure levels.
NRC characterized the finding as a low-to-moderate safety significance based, in part, on the determination that the historical degradation of the valves indicated there was an increased likelihood that the valves would not function when needed.
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