TOKYO: Japanese nuclear power operator said on Friday it would decommission an ageing reactor because of the cost of upgrading, the sixth to be scrapped due to tougher rules brought in after the Fukushima disaster. Japan is pushing to restart its nuclear reactors, which were shuttered after a huge earthquake-triggered tsunami sent the Fukushima Daiichi nuclear plant into meltdown in 2011. But safety regulations brought in after the disaster, which require companies to build structures to guard against huge waves and earthquakes, means it could cost billions to overhaul old reactors. Only two are on line after passing the tests, while power companies have already announced plans to scrap at least five other old reactors. Shikoku Electric Power (SEP) had planned to restart the number one reactor at Ikata nuclear complex in Ehime, western Japan, but said on Friday it would decommission the 39-year-old technology instead.