Kansai Electric Power Co. said Monday that a reactor at its Takahama power plant in Fukui Prefecture shut down automatically after a problem with a generator triggered an alarm.

The No. 4 reactor, which was brought back online last Friday, was deactivated after the automatic alarm system prompted control rods to be inserted. There was no problem with the reactor's cooling system, the company said.

The incident follows a coolant water leak on Feb. 20 in a building attached to the reactor that was caused by insufficient tightening of a bolt in a pipe valve.