Last month, Chimori Naito, a 91-year-old former vice president at Kansai Electric Power Co., admitted what was hardly a secret but which put the utility under intense media scrutiny.

Naito said in a series of interviews with the Asahi Shimbun that he supervised under-the-table cash payments to seven prime ministers and key politicians in the ruling and opposition parties between 1972 and 1990 to ensure favorable policies, especially nuclear power policies. Naito guessed Kepco's annual payoffs were in the hundreds of millions of yen.

Kepco got its money's worth. Prior to March 11, 2011, Japan relied on nuclear power for about a third of its electricity needs. But half of Kepco-supplied electricity came from nuclear power. Fukui Prefecture became home to 11 Kepco reactors, the largest concentration in the country and, perhaps, the world. And it was Kepco's two Oi reactors that were switched back on in the summer of 2012 despite massive public opposition.