Kansai Electric Power Co said it was to suspend reactor 4 at Oi Nuclear Power Station on the Sea of Japan coast later in the day, joining Japan's other 49 units which have already been halted for maintenance or due to accidents, the utility said.
None of Japan's power companies is likely to reactivate their idled reactors this year, because of new safety assessments and procedures for gaining local consent for resuming operations.
Nuclear-generated electricity made up about 30 per cent of Japan's output before the country's worst atomic accident at the Fukushima Daiichi Nuclear Power Station. Japanese utilities have relied more on thermal power generation.