* Further regulatory steps required * May boost prospects for wider reboot * For an interactive graphic on the status of Japan's nuclear reactors, click tmsnrt.rs/2OTpNfA (Adds story links, background) TOKYO, April 28 (Reuters) - Kansai Electric Power received approval to restart three 40-year-old, long-idled reactors, which could pave the way for a revival of a nuclear energy sector largely dormant since the Fukushima disaster a decade ago. The approval on Wednesday from Fukui Prefecture Governor Tatsuji Sugimoto was the first in four years and is needed to allow any return to operation following the post-Fukushima shutdown. It could stir opposition from a public still wary of atomic power, but officials have called for new nuclear plants to help meet government climate targets to decarbonise the country’s heavily industrialised economy.