The Limerick nuclear plant in western Montgomery County on Friday had its third unplanned shutdown this week, but no safety problems were reported, authorities said. Unit 1 at the plant shut down automatically at 10:15 a.m., said Neil Sheehan, a spokesman for the Nuclear Regulatory Commission.

Exelon, the plant owner, identified the cause as a "trip" of the main turbine, Sheehan said. A "trip" occurs when a component or system goes off-line, Sheehan said. The other unplanned shutdowns were Sunday and Monday involving the plant's other reactor. - Robert Moran