The Nuclear and Industrial Safety Agency decided Monday to sign off on the stress test results for an idled reactor at the Ikata power plant in Ehime Prefecture, which will pave the way for a third unit to gain clearance for resuming operations.
In a revised draft report, NISA said the results confirm that Shikoku Electric Power Co. has taken sufficient measures to prevent the reactor from falling prey to a station blackout like the one that crippled the Fukushima No. 1 power plant in Fukushima Prefecture and tainted wide swaths of the northeast with radioactive fallout following an earthquake and tsunami.
Once NISA finalizes the report, the Nuclear Safety Commission, the five-member state body tasked with supervising nuclear safety regulations, will double check its evaluation of the results on the Ikata plant’s No. 3 reactor.
Prime Minister Yoshihiko Noda and three Cabinet ministers will then judge whether to authorize its restart, leaving the ball in Ehime’s court.
The government mandated the two-stage stress tests in light of the Fukushima disaster. Clearing the first stage of the test, which is based on computer simulations, is a precondition for restarting dozens of reactors that have been idled for scheduled checkups.
Only two of Japan’s 54 reactors are online at the moment because many of them, including the one at the Ikata plant, have been idled for routine checkups that by law must be conducted every 13 months. The checkups generally take three to four months.
The two active reactors — unit 6 at Tokyo Electric Power Co.’s Kashiwazaki-Kariwa plant in Niigata Prefecture and unit 3 at Hokkaido Electric Power Co.’s Tomari plant in Hokkaido — will be suspended by early May for such checkups.
Shikoku Electric originally reported that the No. 3 reactor at Ikata is capable of withstanding an earthquake 1.86 times stronger than the most powerful quake “required to be taken into account under the safety criterion.” But the utility later slashed the figure to 1.5 because quake resistance at some facilities was found to be weaker than previously thought.
The two other reactors that have won NISA’s approval are units 3 and 4 at Kansai Electric Power Co.’s Oi plant in Fukui Prefecture.