The upgrades on the reactors, which are all shut for so-called post-Fukushima stress tests, will take four years to complete.
Kansai Electric president Makoto Yagi said to Bloomberg that though he think the company has improved safety to prevent an accident similar to Fukushima, steps to increase safety never end.
"Safety at nuclear plants is our top priority," Yagi said.
Yagi is petitioning the government to allow the resume two reactors at its Ohi plant before summer, Bloomberg reports.
Kansai Electric has warned that if all its reactors stay offline during summer peak power demand, cities it serves, such as Osaka and Kyoto, as well as Sharp Corp, Panasonic Corp and other companies may face power shortages.
