June 30 (Reuters) - The prolonged crisis at the Fukushima Daiichi nuclear power plant has prompted a review of Japan's energy policy and stirred questions about how government officials and industry will deal with the prospect for a power shortage that could stretch into 2012.
Japanese utilities are currently operating 19 of the 54 nuclear reactors that had been available before the March 11 earthquake and tsunami triggered meltdowns and explosions at four of the reactors at Fukushima Daiichi.
The reactors still in operation account for about 36 percent of the pre-disaster nuclear generation capacity of Japanese utilities.
By the end of September, seven of the 19 operating reactors are scheduled to be shut for maintenance. By the end of December, another five are due to shut.
Japan's trade ministry said earlier this month that, without approval to restart reactors now down for maintenance, all of Japan's reactors could be shut by next April, adding more than $30 billion to the nation's energy costs.
In Japan, nuclear generators must shut for inspection at least once every 13 months. The maintenance period can vary from a few months to more than a year, and the restart typically begins with a one- to two-month test run before advancing to commercial operation, which requires regulatory approval.
Kansai Electric's Ohi No.1 unit and Hokkaido Electric's Tomari No.3 unit have been supplying power to customers since March on a test basis. Those two reactors have not yet completed the process for returning to commercial operating status.
The 13-month operating limit begins once a reactor is approved for commercial operation, although limits to fuel life prevent reactors from operating indefinitely.
The list below shows the location of nuclear power plants still in operation and the dates by which each is scheduled to be taken off-line for maintenance.
Kashiwazaki-Kariwa Unit 1
Planned maintenance by Aug. 6, 2011
Kashiwazaki-Kariwa Unit 5
Planned maintenance by Jan. 25, 2012
Kashiwazaki-Kariwa Unit 6
Planned maintenance from March 2012
Kashiwazaki-Kariwa Unit 7
Planned maintenance by Aug. 23, 2011
Mihama Unit 2
Planned maintenance by Dec. 19, 2011
Ohi Unit 1
Planned maintenance expected in or after April 2012
Ohi Unit 2
Planned maintenance by Dec. 17, 2011
Ohi Unit 4
Planned maintenance by July 23, 2011
Takahama Unit 2
Planned maintenance by Nov. 26, 2011
Takahama Unit 3
Planned maintenance by Feb. 21, 2012
Takahama Unit 4
Planned maintenance by July 22, 2011
Genkai Unit 1
Planned maintenance by Dec. 2, 2011
Genkai Unit 4
Planned maintenance by Dec. 26, 2011
Sendai Unit 2
Planned maintenance by Sept. 4, 2011
Shimane Unit 2
Planned maintenance by Jan. 28, 2012
Ikata Unit 1
Planned maintenance by Sept. 5, 2011
Ikata Unit 2
Planned maintenance by Jan. 14, 2012
Tomari Unit 2
Planned maintenance by Aug. 28, 2011
Tomari Unit 3
Planned maintenance expected in or after April 2012 (Compiled by Kevin Krolicki and Osamu Tsukimori in Tokyo; Editing by Edmund Klamann)