Kansai Electric Power Co. is seeking Japanese government approval to decommission units 1 and 2 of its Ohi nuclear power plant. World Nuclear News says that the company will submit a detailed decommissioning plan for the two 1,175 MW pressurized water reactors.

Kansai said in late December that it had decided not to seek permission to restart the two units, which began operating in March 1979 and December 1979.

Ohi 1 and 2 have been offline since July 2011 and December 2011, respectively, and are the only reactors in Japan to feature ice condenser emergency cooling systems. These systems use blocks of ice in a basket installed around the containment vessel to cool steam generated to reduce pressure in the event of an accident.

Kansai said that to comply with new safety standards, the walls of the containment buildings would need to be thickened. Reports say that Kansai estimated it would have cost some $7.3 billion to make safety upgrades.

Kansai Electric Power Co. operates in the Kansai region, which includes the Kobe-Osaka-Kyoto megalopolis. The Kansai region is Japan’s second-largest industrial area. Before the Fukushima Daiichi accident in March 2011, 11 nuclear reactors supplied almost 50 percent of the region’s power.

As of March 1, Ohi units 1 and 2 are classed as shut down, reducing the overall rated generating capacity of the plant from 4.75 GW to 2.36 GW.

The utility will now formulate a detailed decommissioning plan for Ohi 1 and 2, which it will submit to the Nuclear Regulation Authority for approval.

Following the shutdown of all of Japan's reactors after the Fukushima accident, Kansai was given permission to resume operation of the newer units 3 and 4 of the Ohi plant in August 2012. The two 1,180 MWe PWRs were taken offline for inspections in September 2013, World Nuclear News says. The utility has received all necessary approvals to restart both units, and reloaded fuel into unit 3 with plans to return both units to commercial operation by mid-2018.