The Nuclear Industrial and Safety Agency validated on Friday the results of a safety test on an idled reactor at the Ikata power plant in Ehime Prefecture.
In a draft report to an advisory panel, NISA says measures have been taken to prevent an accident even if it is hit by a quake or tsunami similar to those that struck the Fukushima No. 1 plant.
If the report is finalized, the No. 3 unit at the Shikoku Electric Power Co. plant will be the third reactor to receive NISA's approval for the first round of stress tests instituted after the Fukushima crisis erupted.
The draft report says the results of the computer-simulated safety test suggest the utility has taken adequate measures to protect the reactor.
The stress test checks a reactor's ability to withstand earthquakes and tsunami.
NISA approved the results of similar safety tests last month for reactors 3 and 4 at Kansai Electric Power Co.'s Oi plant in Fukui Prefecture.
Shikoku Electric originally reported that reactor 3 at the Ikata plant is capable of withstanding an earthquake 1.86 times stronger than the most powerful quake required under the safety criteria. But the utility later lowered the figure to 1.5 after some facilities were found to be weaker than thought.
If NISA finalizes the report, it will be submitted to the Nuclear Safety Commission to be double checked. Prime Minister Yoshihiko Noda and other ministers will decide whether the reactor can be restarted after taking into account the opinions of nearby communities.