The nuclear reactors at these plants were halted following the catastrophic March 2011 earthquake and tsunami that crippled the Fukushima-Daiichi plant and set off Japan's worst nuclear crisis.
Kyodo News also reported Kansai Electric Power Co.'s Oi nuclear power station in central Japan's Fukui prefecture, whose two reactors are the only ones currently in operation, is also scheduled to be idled in September for inspection.
Utility operators of Japan's nuclear plants would be required to comply with new safety guidelines to be announced in July by the country's Nuclear Regulation Authority.
The nine regional utilities and Japan Atomic Power Co. in the Kyodo survey also estimated it would cost them at least $11.7 billion to comply with the new safety standards.
One utility said its cost alone would be about $3 billion in the medium to long term, the survey said.
Kyushu Electric Power Co., one of the survey respondents, said it could restart two of its reactors by July provided the regulatory agency completes its inspections. The survey said other companies declined to provide specific dates for restarting their plants.
Since the March 2011 disaster, 48 of Japan's 50 nuclear reactors have been idled.
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