The utility operating the sole reactor at the Tokai No. 2 nuclear power plant in Ibaraki Prefecture on Friday filed for state approval to extend the unit's operation beyond the government-mandated 40-year limit.

It is the fourth time that an application has been filed with the Nuclear Regulation Authority to extend the operation of an aging reactor for an additional 20 years, but the latest request is the first for a boiling water reactor — the same type as at the crisis-hit Fukushima No. 1 nuclear complex.

The application for the Tokai plant, currently offline, comes despite local governments lacking emergency plans to evacuate around 960,000 people living within 30 km of the plant. Of all the nuclear power plants in Japan, Tokai has the most densely populated surrounding area.