Entergy’s Pilgrim Nuclear Power Station was still shut down Thursday following a malfunction two days earlier in which excessive water levels were recorded in the plant’s reactor vessel, the latest failure for the Massachusetts facility.
Nuclear Regulatory Commission spokesman Neil Sheehan said by email Tuesday the reactor shut down because of a high water level “resulting from an oscillating (fluctuating) feedwater regulating valve.” Water is pumped into the reactor vessel so that it can be boiled, converted to steam, and then piped to the turbine to generate electricity, Sheehan explained.
Entergy spokesman Patrick O’Brien said by email Thursday that the plant remains offline, but is in “safe and stable condition,” adding that all systems responded as expected during the shutdown.
“At no time was the health and safety of the public or plant challenged,” O’Brien wrote. “A detailed investigation of the cause and subsequent repair plan is underway. The information on our return to 100% power is business sensitive and proprietary and we are therefore not at liberty to make the day and time public.”
Sheehan said Thursday that NRC is continuing to monitor Entergy’s work as it determines what caused the malfunction and what repairs might be necessary. Entergy, citing economic hardship, plans to shut Pilgrim down in May 2019.
Sheehan said NRC is not currently considering taking any action against the plant.
“However, our overall heightened oversight at Pilgrim is continuing,” he wrote Tuesday, referring to three increased oversight inspections either conducted or scheduled at the facility to determine whether it should remain operable. “And the largest and most comprehensive component of that oversight will take place later this year and into next year. … (Inspectors) will continue to keep a close eye on Entergy’s troubleshooting activities and any repair plans.”
On Aug. 21, plant operations also stopped “to allow for repairs to a main steam isolation valve,” the Boston Globe quoted Sheehan as saying.
The NRC in September 2015 downgraded the plant’s safety rating to Column 4, the lowest rating a nuclear facility can have while remaining in operation. The agency has since performed two of the three inspections at the site. The NRC in those inspections found no significant issues, though both times inspectors registered “green” findings, which signify issues of “very low safety significance.” The first concerned water leakage from the core spray system, and the second stemmed from a maintenance procedure failure for a salt service water pump.
The third and potentially final inspection at Pilgrim is expected later this year or in early 2017, according to Sheehan. The plant is scheduled for refueling in spring 2017.
The NRC announced on Sept. 2 that it had issued half-year performance assessments to America’s 99 operating nuclear power plants, and Pilgrim joined two other Entergy-owned reactors (Arkansas Nuclear One units 1 and 2) in registering the worst grades.
Citing “long-standing performance issues of low-to-moderate safety significance,” the NRC listed Pilgrim in the fourth performance category for the six-month period ending June 30. Of the 96 highest-performing reactors, 87 met all safety and security performance objectives, according to an NRC press release.
