With the reactor at full power, the Pilgrim Nuclear Power Plant went into automatic shutdown Saturday afternoon. According to a release from Entergy, the company that owns Pilgrim, the shutdown occurred around 4:30 p.m.
The automatic shutdown was prompted by the closure of a single main steam isolation valve (MSIV). Four main steam lines carry steam from the reactor to the turbine-generator and the valve automatically isolates the reactor from the turbine-generator, the release said.
"All other plant systems responded as designed," said Lauren Burm, Senior Communications Specialist at Pilgrim.
Entergy is investigating the cause of the MSIV closure.
The Pilgrim Nuclear Power Plant is currently shutdown. The release did not indicate how long the plant will remain disconnected from the grid.
The last unplanned shutdown, or scram, at the Plymouth plant occurred in May.