Safety screenings by the Nuclear Regulation Authority are making progress, especially on 12 pressurized water reactors at six nuclear power plants.
The NRA has received safety check applications concerning 20 reactors at 13 plants - including Kyushu Electric Power Co.'s Sendai plant in Kagoshima Prefecture, which obtained local government approval on Friday for restarting its reactors. Passing NRA safety screenings is a condition for restarting idled reactors.
The 12 pressurized water reactors feature relatively large containment vessels.
Among the 12, the NRA has begun work to create documents that would grant the Nos. 3 and 4 reactors at Kansai Electric Power Co.'s Takahama nuclear power plant in Fukui Prefecture passing grades for their safety checks.
Worst-case scenarios for earthquakes and tsunami complied by utilities are critical for the safety screenings.
The NRA has mostly finished examining such quake and tsunami scenarios for the Nos. 3 and 4 reactors at Kyushu Electric Power Co.'s Genkai power plant in Saga Prefecture, as well as the Nos. 3 and 4 reactors at Kansai Electric's Oi plant in Fukui Prefecture and the reactors at the Sendai and Takahama plants.
The watchdog is likely to make a conclusion soon on the No. 3 reactor at Shikoku Electric Power Co.'s Ikata plant in Ehime Prefecture as well.
Meanwhile, safety screenings for eight boiling water reactors at seven nuclear power plants - of the same type as the reactors at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant, where the 2011 earthquake and tsunami triggered a nuclear crisis - are taking more time.
The NRA has called for installing exhaust vents with filters for radioactive materials to reduce pressure in the containment vessels of boiling water reactors.
The NRA is trying to enhance screening efficiency by steps such as looking into related issues at the same time.
However, prospects for the NRA ending its safety screenings quickly on the eight reactors remain uncertain.
Besides the reactors currently undergoing the safety screenings, seven others reactors at five plants, such as the about 40-year-old Nos. 1 and 2 reactors at Kansai Electric's Mihama plant in Fukui Prefecture, have also drawn public attention as to whether they will be decommissioned.