The Pilgrim Nuclear Power Plant shut down because of a steam leak in a valve.
The shut down ended up being a controlled shut down compared to a scram, said Nuclear Regulatory Commission (NRC) officials. A scram is a sudden shutdown, in which all the control rods rapidly insert into the reactor and the fission process halts.
Officials discovered the steam leak in a check valve, part of the cooling system, while the reactor was operating at 50 percent of capacity for unrelated reasons, said Carol Whitman, spokesperson for the Plymouth, MA, facility.
Operators could not turn off or shut down the leaking valve by shutting the valves leading to it and halting the leakage, said NRC Spokesman Neil Sheehan.
If operators can isolate a valve or line in that manner, it’s possible to make repairs without removing the plant from service.
The leaking valve was in the main steam tunnel, which carries steam lines from the reactor to the turbine.
The plant’s technical specifications have specific limits on the allowable leakage from this type of valve.
“If the leakage could not be halted within 24 hours, the plant had to be shut down, which is what occurred,” Sheehan said.
Until Entergy performs an examination of the leaking valve, it is too early to characterize the cause of the leak. And there is no timeline on the repairs.
The NRC expects Entergy to be as thorough as possible in fixing the valve and will be following up to ensure that has occurred, Sheehan said.