Factbox: Shutdown schedule for 9 active nuclear reactors

(Reuters) - The crisis at the Fukushima Daiichi nuclear plant after a massive earthquake and tsunami in March has prompted a review of Japan's energy policy and raised questions about how government officials and industry will deal with the prospect of power shortages that are to stretch into 2012.

Kyushu Electric Power Co, one of the country's most highly nuclear reliant regional power firms, on Thursday started regular maintenance on the No.1 unit at its sole Genkai nuclear plant, as planned, leaving only nine reactors online.

A total of 54 nuclear reactors had been available for commercial use before the March 11 earthquake and tsunami disabled cooling systems at Fukushima Daiichi, run by Tokyo Electric Power Co, triggering meltdowns and causing the world's worst radioactive material leakage in 25 years.

No reactor shut for regular maintenance has restarted since the March 11 disaster amid public concerns over atomic energy and the government's reassessment of safety regulations.

Kansai Electric and Shikoku Electric Power Co have submitted the results of newly required stress tests on a total of three reactors, taking the initial step to regain public faith in atomic energy.

Without approval for restarts, all of Japan's reactors could be shut by next May, boosting the usage of fossil fuels and adding more than $30 billion a year to the nation's energy costs.

In Japan, nuclear generators must be 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 operations, a step which requires regulatory approval.

Following are the locations of nuclear power plants still in operation and the companies' schedules for shutdowns. If the utility has not given a schedule, the dates by which each reactor has to be taken offline for maintenance are listed, according to Reuters calculations.

Kansai Electric

Ohi No.2, 1,175 MW

Planned maintenance from December 16, 2011

Kansai Electric

Mihama No.2, 500 MW

Planned maintenance from December 18, 2011

Kyushu Electric

Genkai No.4, 1,180 MW

Planned maintenance from December 25, 2011

Shikoku Electric

Ikata No.2, 566 MW

Planned maintenance from January 13, 2012

Tokyo Electric

Kashiwazaki-Kariwa No.5, 1,100 MW

Planned maintenance from January 25, 2012

Chugoku Electric

Shimane No.2, 820 MW

Planned maintenance by January 28, 2012

Kansai Electric

Takahama No.3, 870 MW

Planned maintenance from February 20, 2012

Tokyo Electric

Kashiwazaki-Kariwa No.6, 1,356 MW

Planned maintenance from March 10, 2012

Hokkaido Electric

Tomari No.3, 912 MW

Planned maintenance from April-May 2012

(Compiled by Osamu Tsukimori and Risa Maeda; Editing by Joseph Radford)