Insight Web Extra
July 2009—Japanese electric utility Tokyo Electric Power Co. (Tepco) has restarted one of seven shutdown nuclear reactors at the Kashiwazaki-Kariwa plant after an extended shutdown period following a strong earthquake two years ago this July.
Detailed checks prior to the startup revealed no technical issues and confirmed the unit's soundness to resume operations after a 22-month hiatus.
All seven reactors at the Kashiwazaki nuclear plant, the largest in the world with a total capacity of more than 8,200 megawatts, have been down since an earthquake centered just 10 miles offshore from the plant revealed insufficiencies in their seismic design basis.
Although the 6.8-scale quake was stronger than the plant was originally designed to withstand, there was no damage to the nuclear components and no injuries at the plant site. However, to account for unexpectedly large ground motions during the quake, TEPCO initiated a revision of its seismic analysis for the plant and conducted a thorough geological survey.
An extended series of inspections by Japanese regulatory authorities and by the International Atomic Energy Agency (IAEA) have kept the plants shut down until the recent startup of Unit 7 in May.
Tepco said in a May 8 statement that it received restart approvals from Niigata prefecture governor Hirohiko Izumida, Kashiwazaki mayor Hiroshi Aida and Kariwa mayor Hiroo Shinada.
According to Tepco, the other six units will be brought online one by one as the utility confirms the “soundness of facilities, restoration works, seismic reinforcement works, etc."
Meanwhile, the nuclear trade association Japan Atomic Industrial Forum (JAIF) announced that the country’s nuclear reactor fleet had the lowest average capacity factor in ten years—60 percent from April 2008 to March 2009. A major contributing factor to this was the Kashiwazaki-Kariwa shutdown, JAIF said.
Kashiwazaki-Kariwa’s seven large reactors alone account for more than 2 percent of world nuclear capacity, and their shutdown resulted in a corresponding drop in 2008’s nuclear share of world electricity supplies to 14 percent, from an average of 16 percent seen in the previous 5 years, according to IAEA and World Nuclear Association data.
Japan’s 53 nuclear reactors have historically provided about 30 percent of the country’s electricity. The Japanese Ministry of Economy, Trade and Industry (METI) said recently that Japanese power utilities need to increase the share of electricity produced from nuclear plants to about 40 percent, if the country is to start meeting its greenhouse gas reduction goals.
Unit 3 of the Tomari nuclear power plant came started up early in March, and will start producing electricity commercially this December, after a 6-year construction period. This will help Japan meet its stated goals to generate at least half of its power from zero-emission sources by 2020.
Three of seven nuclear reactors at Japan’s 8,200 megawatt Kashiwazaki-Kariwa nuclear power station, the world’s largest. [Image credit: Tepco]
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