By Risa Maeda
TOKYO (Reuters) - Three of Japan's major cities called for Kansai Electric Power Co, its second largest nuclear generator, to draw up a plan to switch to other energy sources nearly a year after the country suffered the world's worst nuclear accident in 25 years.
The mayors of Osaka, Kobe and Kyoto, home to a total of 5.7 million people, on Monday submitted questions on prospects for alternative energy supplies and price incentives to curb demand.
The cities hold a total 12 percent stake in Kansai. Nuclear power accounted for 44 percent of demand in Kansai's base in western Japan in the year to March 2011 -- making it the country's most nuclear-dependent utility.
Only two of Japan's 54 nuclear reactors are on stream after an earthquake and tsunami crippled the Fukushima Daiichi plant, run by Tokyo Electric Power Co., or Tepco, the largest nuclear operator.
Many are stopped for regular maintenance and must undergo "stress tests" before they are restarted.
The mayors also expressed concern about the vulnerability of any utility relying on a single power source. Tepco had to introduce rolling blackouts after last March's disaster and imposed power saving measures on large users.
"In light of the March 11 incident at the Fukushima Daiichi nuclear plant...should a critical incident hit Kansai Electric Power Co's region...it is clear that citizens' lives and economic activities would be greatly affected," the mayors said in their submission to Kansai Electric's president, Makoto Yagi.
"We should therefore create a power supply system not dependent on nuclear power as early as possible."
The mayors' move could prompt other shareholders to follow suit.
A government official in Osaka, whose Mayor Toru Hashimoto has become increasingly forthright in opposing nuclear power, said the cities sought a reply by March 15. They would then decide on making a proposal to a general shareholder meeting.
Japan has abandoned a 2010 plan to boost the share of nuclear power to more than 50 percent of demand by 2030 as authorities debate the future role of atomic energy.
The central government is, however, keen to get some reactors running again to avoid a potentially damaging power shortage during periods of high demand in the summer.
Kansai Electric wants to restart at least two of its 11 reactors, now all offline, after the nuclear watchdog this month said the units "passed" stress tests - computer simulations evaluating reactions to severe events.
Local governments must also give their clearance for what would be the first reactors to restart since the disaster. Tests on 14 reactors run by eight utilities are under review.
Without approval for restarts, all reactors could be shut by early May, boosting the use of fossil fuels and adding over $30 billion a year to energy costs, according to the government.
Opinion polls last year showed about three-quarters of the public want at least a gradual exit from nuclear power. Osaka activists are seeking a referendum on scrapping atomic power, though enthusiasm for campaigning overall appears to be waning.
One survey by Nikkei electronic media this month showed 48 percent support for the restart of reactors to meet short-term needs.
(Editing by Ron Popeski and Anthony Barker)