Tokyo (Platts)--30Aug2011/531 am EDT/931 GMT

Only 11 nuclear reactors will be operating in Japan with a combined power generation capacity of 9.864 GW in early September, which represents 20% of the country's total installed capacity of 48.96 GW spread over 54 reactors, according to Platts calculations Tuesday.

Platts calculations were made as Japan's Kyushu Electric and Shikoku Electric are scheduled to shut two nuclear reactors in western Japan in early September.

Japan's Kyushu Electric said Tuesday it plans to start three-month-long scheduled maintenance at its 890 MW No.2 Sendai nuclear power plant in the country's southwest on September 1.

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This is in response to Japanese regulations that require nuclear power plants to carry out scheduled maintenance at their reactors at least once every 13 months.

This means that Kyushu Electric's operational nuclear power generation capacity will fall to 1.739 GW in September over two units, from 2.629 GW currently, which represents 33.1% of the company's total installed nuclear capacity of 5.258 GW across six units.

Shikoku Electric said Tuesday it plans to start scheduled maintenance at its 566 MW No. 1 reactor by shutting down the reactor on September 4 at its sole Ikata nuclear power plant in western Japan.

This means that Shikoku Electric's operational nuclear power generation capacity will fall to 566 MW GW in September at one unit, from 1.132 GW currently, which represents 28% of the company's total installed nuclear capacity of 2.022 GW across three units.

Shikoku Electric plans to restart the Ikata No. 1 nuclear reactor on November 16 with an eye to completing scheduled maintenance on December 15. But the company noted that it may have to extend its maintenance amid uncertainty over any nuclear reactor restarts in the country in the wake of the March 11 earthquake.

On August 26, Hokkaido Electric shut the 579 MW No. 2 nuclear reactor at its sole Tomari nuclear power plant in northern for scheduled maintenance.

Japan is currently in the middle of its summer power demand season, which typically runs July-September. Weather and nuclear utilization rates have a direct impact on crude, fuel oil and LNG consumption for thermal power generation in Japan.

Tokyo Electric Power Company and Tohoku Electric lost more than 11 GW of nuclear capacity at their Fukushima and Onagawa facilities, respectively, due to the devastating earthquake and tsunami in the northeast March 11.

Only one nuclear plant, which was restarted before the March earthquake, has been allowed to resume commercial operations since then, and there are widespread expectations in Japan that none of the shut nuclear plants will be allowed to restart any time soon because of the uncertain stress test conditions imposed by the government in July.

If none of the nuclear reactors are allowed to restart in the coming months, Japan is scheduled to lose its nuclear output completely in April or May 2012 because of the Japanese regulation that requires nuclear power plants to carry out scheduled maintenance at their reactors at least once every 13 months.

If this happens, it would be the first time Japanese nuclear power production has fallen to zero since it commenced in 1966.

--Takeo Kumagai, takeo_kumagai@platts.com