Japan's nuclear watchdog gave approval Wednesday for the nation's third reactor to operate beyond the mandated 40-year maximum life span as the enforcement of limits introduced after the Fukushima disaster continues to weaken.

The No. 3 unit at Kansai Electric Power Co.'s Mihama plant in Fukui Prefecture is the latest reactor given the approval following two units at the utility's Takahama complex, also in Fukui.

The 40-year operational limit was part of tougher safety requirements introduced by the Nuclear Regulation Authority after the Fukushima disaster. It was meant to encourage operators to retire aging reactors that could be prone to accidents.