Kansai Electric Power Co.’s Takahama No. 4 reactor in Fukui Prefecture on Friday became the nation’s fourth to be restarted since 2012 and the first to burn MOX, a mixed-oxide fuel that contains plutonium.

In a statement released Friday afternoon, Kepco President Makoto Yagi said safety would remain the top priority and that the utility would continue to promote safety standards beyond what was legally required.

The startup came nearly a week after a radioactive water leak was discovered at the reactor’s auxiliary building on Feb. 20. Kepco halted restart preparations while it repaired the leak, saying it did not pose a danger to the environment.

The utility said earlier this week the leak was caused by a loose pipe valve and could be repaired without affecting the restart schedule, which called for rebooting the unit by the end of this month.

Under Kepco’s schedule for the restart process, the No. 4 reactor is expected to start generating electricity by Monday afternoon and reach full power a few days later. Once the Nuclear Regulation Authority gives final approval, and assuming there are no last-minute technical problems, the plan is to have it back online and selling electricity from late March, just before the end of fiscal 2015.

The restart of Takahama No. 4 comes about a month after the nuclear power plant’s No. 3 reactor was restarted. Along with two reactors at Kyushu Electric’s Sendai plant, which went back online last August, they comprise the four reactors that have been restarted since beefed-up nuclear safety standards took effect in 2012.

In addition to No. 3 and No. 4, which are at least 30 years old, Kepco also wants to restart Takahama Nos. 1 and 2, both of which are over 40. It hopes to run them for up to two decades. Despite concerns about the increased probability of accidents at the aged plants, their restart moved a step closer to reality on Wednesday, when the NRA said additional safety systems Kepco installed to extend the reactors’ life spans met its standards.

The next step will be soliciting public comment, and then further permission from the NRA is required for what would be the first-ever extensions in Japan of reactors over 40 years old.

Before that happens, Kepco will seek final permission from the mayor of Takahama and the governor of Fukui Prefecture for the restart, which could be a lengthy process. The utility may also find itself forced to deal with public and political concerns in surrounding Kansai prefectures like Shiga and Kyoto, where safety concerns about the aged reactors are strong.

http://www.japantimes.co.jp/news/2016/02/26/national/japan-restarts-fourth-atomic-reactor-since-2012-moratorium/#.VtC5r-bzN_l