The Nuclear Regulation Authority has adopted a draft certification that the No. 1 and No. 2 reactors at Kansai Electric Power Co.'s Takahama nuclear power plant in Fukui Prefecture meet the post-Fukushima nuclear safety standards — effectively giving its basic safety clearance for reactors that have already passed the legal threshold of 40 years in operation. Pending additional procedures, the two reactors may become the first to have their operation extended beyond the 40-year limit set after the 2011 disaster at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant. The NRA's decision risks undermining the rule that reactors, in principle, be decommissioned after they have been in operation for 40 years.

The law regulating nuclear reactors was revised in 2012 — under the previous Democratic Party of Japan-led government — to establish the rule prohibiting reactors from being operated for more than 40 years. But it also allowed a one-off extension of up to 20 more years upon receiving a safety clearance from the NRA, which the following year put into force more stringent safety standards on nuclear power plants.

The rule set a grace period for power firms to get the NRA's nod for the extension — up to this July for the two aging Takahama reactors. Eleven reactors — five that have passed or were nearing the 40-year period, along with the six at Tepco's Fukushima No. 1 plant — have since been decommissioned.