OSAKA – The No. 3 reactor at Kansai Electric Power’s Oi nuclear power plant in Fukui Prefecture has stopped automatically after an alarm went off, the company said in the small hours of Sunday.

While the cause of the incident is under investigation, no leakage of radioactive substances has occurred, according to the firm, which serves the Kansai region.

An alarm sounded around 11:55 p.m. Saturday, indicating an abnormality in a device to generate a magnetic field at the reactor’s power generator connected to a turbine, and the power generator and the reactor stopped automatically, Kansai Electric said.

Thirty-five years will have passed in December since the start of operations at the 1.18-million-kilowatt pressurized water reactor. A regular checkup has been slated to begin in October.

In April 2000, a glitch at a device of the same kind led the power generator of the No. 2 reactor at the firm’s Mihama nuclear plant in Fukui Prefecture and the reactor to shut down automatically. The reactor is now in the process of decommissioning.