Inside the Kashiwazaki-Kariwa Nuclear Power Plant

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The Kashiwazaki-Kariwa Nuclear Power Plant (柏崎刈羽原子力発電所 Kashiwazaki-Kariwa genshiryoku-hatsudensho?, Kashiwazaki-Kariwa NPP) is a large, modern (housing the world’s firstABWRnuclear power plant on a 4.2-square-kilometer (1,038 acres) site[1] including land in the towns of Kashiwazaki and Kariwa in Niigata PrefectureJapan on the coast of the Sea of Japan, from where it gets cooling water. The plant is owned and operated by The Tokyo Electric Power Company (TEPCO).

It is the largest nuclear generating station in the world by net electrical power rating. It was approximately 15 miles from the epicenter of the second strongest earthquake to ever occur at a nuclear plant, the Mw 6.6 July 2007 Chūetsu offshore earthquake. This shook the plant beyond design basis and initiated an extended shutdown for inspection, which indicated that greater earthquake-proofing was needed before operation could be resumed.

The reactors at the KK plant were shut down one by one after the discovery of deliberate falsification of data. The first one was taken offline September 9, 2002, and the last one was taken offline January 27, 2003.[4] The newest units, the more inherently safe ABWRs, were taken back online the quickest and suffered the smallest effect. Units  1, 2, and 3 on the other hand, generated no electricity whatsoever during the entire fiscal year of 2003.

All reactors continue to use low-enriched uranium as the nuclear fuel; however, there have been plans drafted by Tepco to use MOX fuel in some of the reactors by the permission of the Japanese Atomic Energy Commission (JAEC). A public referendum in the Kariwa village in 2001 voted 53% against use of the new fuel. After the 2002 Tepco data fabrication scandals, the president at the time, Nobuya Minami, announced that plans to use the MOX fuel at the KK plant would be suspended indefinitely.

By Japanese law (and other countries have similar reporting), utilities operating nuclear plants must report certain kinds of events (power excursions, high dose to a worker, or accidents) to the NISA and METI. Some of the events listed below didn’t necessarily fit this category but Tepco decided to officially report them anyway.

  • In May 2000, Unit 6 had to be shut down as a precautionary measure when increased concentrations of Iodine were detected in the coolant loop.
  • On June 12, 2004, the vacuum in the condenser in Unit 1 began to decrease. The operators reduced power, and the condenser pressure stabilized so the unit was run at the lower power of 800 MW for some time.
  • On February 4, 2005, Unit 1 was manually shut down due to leakage of steam in the lower floor of the turbine room.
  • On July 3, 2005, the Unit 5 reactor tripped by a turbine trip caused by a decreased vacuum in the condenser (turbine trip occurs to protect the turbine).
  • On May 26, 2006, Tepco and the Chūbu Electric Power Company submitted a report about cracking in the hafnium control blades.
  • On July 12, 2006, it was discovered that a worker was exposed to radiation above the 0.8 millisievert legal limit in one day, receiving 1.03 millisieverts.
  • On July 16, 2007, the 2007 Chūetsu offshore earthquake caused severe damage to parts of the plant, resulting in small radioactive releases, complete shutdown and seismic upgrades.
  • On September 20, 2007, a temporary air conditioner on the roof of the plant caught fire, but there was no danger of a radioactive leak.[50][51]
  • On May 22, 2008, TEPCO announced that earthquake resistance standards needed to be increased by a factor of five and work to reinforce the reactors would begin in June.[52]
  • On August 5, 1011, in the afternoon the output of reactor 1 was reduced, and the next day the reactor would stop completely. This was done for a 2-month inspection. It was the first reactor run by TEPCO, to undergo an inspection since the nuclear accident at the Fukushima. Another reactor at the Kashiwazaki-Kariwa plant was scheduled for a regular inspection late August 2011. Niigata Governor Hirohiko Izumida said, that he won’t give permission for any restart of a reactor, before the cause of the accident at the Fukushima plant would be revealed.
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