Reactor 3 at Tomari Nuclear Power Plant in Hokkaido will be shut down for the scheduled maintenance around midnight on May 5.
Tomari's Reactor 3 is a Pressurized Water Reactor that started operation in 2009. Tomari Nuclear Power Plant is one of the newer nuclear power plants in Japan; the first reactor started operation in 1989. Reactor 3 plans to start using MOX fuel, but a third-party investigation revealed that the plant operator Hokkaido Electric (HEPCO) had used "shills" in one of the "town hall meetings" for the local residents in July last year to speak favorably of and promote the use of MOX fuel (according to the company announcement in October last year).
Hokkaido's governor Harumi Takahashi is a former career bureaucrat in the Ministry of Economy, Trade and Industry, and she wants to restart the nuclear plant as soon as possible.
From Mainichi Shinbun (5/4/2012):
Reactor 3 at Tomari Nuke Plant stops on May 5, no nuke plant operating in Japan for the first time in 42 years
Reactor 3 at Tomari Nuclear Power Plant operated by Hokkaido Electric (located on Tomari-mura in Hokkaido, 912 MW), the only operating reactor among 50 reactors in Japan, will stop on May 5 night due to the scheduled maintenance. The last time all the nuclear reactors in Japan stopped was 42 years ago in 1970, when there were only two reactors and they stopped at the same time for inspection. The national government wants to re-start Reactors 3 and 4 at Ooi Nuclear Power Plant operated by Kansai Electric (located in Ooi-cho in Fukui Prefecture), but it is not certain whether the local municipalities agree to the restart. There is a possibility that Japan will enter summer with high electricity demand with "zero nuclear reactors operating".
According to HEPCO, Reactor 3 has been gradually lowering the output since April 28 in preparation for the inspection. At about 5PM on May 5, the control rods will be gradually inserted in the reactor to stop the nuclear fission, and power generation will stop at about 11PM. At about 2AM on May 6, the control rods will be fully inserted to stop the reactor. In the afternoon on May 7, the cold shutdown will be achieved whereby the temperature of water inside the reactor drops below 100 degrees Celsius.
The number of nuclear reactors in Japan is now 50, after four reactors (1, 2, 3 and 4) at Fukushima I Nuclear Power Plant have been formally declared for decommissioning.
Kansai Electric has been warning the planned blackouts if Ooi Nuclear Power Plant is not restarted by summer. Anti-nuclear net citizens are saying, "Bring it on!"