Kashiwazaki-Kariwa Nuclear Power Plant

From Wikipedia, the free encyclopedia

Aerial view of area, the plant's controlled area where waste heat is dumped into the ocean can be seen fairly clearly.

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 two Generation III reactors) nuclear power plant located in the towns of Kashiwazaki and Kariwa in the Niigata Prefecture, Japan. The plant is owned and operated by The Tokyo Electric Power Company, which is the 3rd largest electric utility in the world.

The plant is notable for being the largest nuclear generating station in the world by net electrical power rating, as well as withstanding the strongest earthquake to ever hit a nuclear plant, the 2007 Chūetsu offshore earthquake.

The plant is located directly on the coast of the Sea of Japan, from where it gets cooling water. There are 7 units, which are all lined up along the coast line. Numbering starts at unit 1 with the south-most unit up to unit 4, then there is a large green space in between unit 4 and 5, then it continues with units 6 and 7 the newest of the reactors.

The plant's electrical output of 8,212 MW is sufficient to provide electricity to about 16 million households. Since there are some 47 million households reported by the Japanese census (see Demography of Japan), this makes the Kashiwazaki-Kariwa NPP an extremely important cornerstone in the electricity market of Japan. Furthermore, this gives the KK NPP the title of the 4th largest electric generating station in the world, behind 3 hydroelectric plants:

1. Itaipu 14,750 MW, Brazil/Paraguay
2. Three Gorges Dam 11,360 MW, China (22,500 MW after completion)
3. Guri Dam 10,055 MW, Venezuela

[edit] Reactors

The power installation costs for units at this site well reflect the general trend in costs of nuclear plants. Capital costs increased through the 80s but have become cheaper in modern times. The last two units were the first Advanced Boiling Water Reactors ever built.

[edit] Fuel

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 atomic energy commission. 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.

[edit] Earthquake Resistance

The foundation of the plant goes through an unstable layer of sand sand down to a a sturdy layer of bedrock, and thus the foundation was very deep. Four stories are underground currently as a result of this. The large portion underground also supposedly makes it less likely to suffer large sways due to resonance vibrations. As with other Japanese power plants, the plant was built according to strict earthquake-resistance standards which are regulated by the law and the atomic energy commission.

In 2006, the safety standards for Japan's nuclear plant's earthquake resistance were modified and tightened. After the 2007 earthquake, suspicions arose that another fault line may be closer than originally thought to the plant, and possibly running straight through the site.

[edit] 2004 Chūetsu Earthquake

In the 2004 Chūetsu earthquake on November 4, 2004, devices around the base of the plant only measured 4 on the Japanese seismological intensity scale while other nearby places measured 6.

All of the reactors except for Unit 4 were operation normally at the time of the earthquake and continued to do so through the quake, Unit 4 was shut down due to routine maintenance. Unit 7 shut down during an aftershock because the turbine thrust bearing wear trip signal was activated.

[edit] 2007 Chūetsu offshore earthquake

Wikinews has related news:

Nuclear leaks after Japan quake are worse than first reported

The KK plant was 19 kilometers away from the epicenter of the 2007 Chūetsu offshore earthquake, which took place 10:13 a.m., July 16, 2007. Shaking of the magnitude of 6.8 m/s² (6.8 on the Richter scale) was recorded in Unit 1 in the east-west direction, above the design specification for safe shutdown of 4.5 m/s², and well above the rapid restart specification for key equipment in the plant of 2.73 m/s².^[2] Units 5 and 6 also recorded shaking over this limit.^[3] Shaking of 20.58 m/s² was recorded in the turbine building of unit 3.^[4] Those nearby saw black smoke,^[5] which was later confirmed to be an electric transformer that had caught fire at Unit 3.^[6] Units 2, 3, 4, and 7 all SCRAMed, while units 1, 5, and 6 were already shut down for the purpose of inspection. The fire at the transformer had been put out by noon on the day of the quake, about 2 hours after it started. The 3-story transformer building was nearly completely charred.^[7] Power failures were reported in over 21,700 houses.^[6]

TEPCO was ready to restart some of the units as of the next day, but the trade ministry ordered for the plant to remain idle until additional safety checks could be completed. On Wednesday, July 18, the mayor of Kashiwazaki ordered operations at the plant to be halted for 'safety reasons' until its safety could be confirmed.^[8] The Nikkei reported that government safety checks could delay the plant for over a year, without stating the source of the information.^[9] In 2005, a reactor at the Onagawa NPP was closed for 5 months following an earthquake.^[9]

A team from the International Atomic Energy Agency arrived at the plant on Sunday August 5 to carry out a four day inspection. The two staff and four experts in seismic safety expect to leave again on August 11, as investigations by Japan´s Nuclear and Industrial Safety Agency (NISA), Nuclear Safety Commission (NSC) and the Tokyo Electric Power Company (TEPCO) continue.^[10]

[edit] Radiation Releases

Initially, it was thought that some water (estimated to be about 1.5 L) from the spent fuel pool leaked into the Sea of Japan as a result of the quake.^[11][12] Later, more detailed reports confirmed a number of releases, though most of them were far less active than common natural radiation sources. According to the Nuclear and Industrial Safety Agency, this was the first time a release of radioactive material happened as a result of an earthquake.

• 0.6 liters of slightly radioactive water leaked from the third floor of the Unit 6 reactor building. This contained 280 Becquerels of activity. (For reference, a household smoke detector emits about 35,000 Becquerels.^[13])
• 0.9 liters of slightly radioactive water leaked from the inner third floor of the Unit 6 reactor building, containing 16,000 Bq.
• From unit 6, 1.3 cubic meters of water from the spent fuel pool leaked from the pool, and flowed into through a drainage pipe, ultimately into the Sea of Japan. The water contained 80 Bq/L, totaling 90,000 Bq in the release. ^[14] Furthermore, an Onsen located in Misasa, Tottori, Japan uses water with a large concentration of Radon, which gives it a radioactivity of 9300 Bq/L. The leaked water from the plant did not pose a health risk even before being diluted. Towels were used to mop up the water.^[15]
• On Wednesday June 18, at Unit 7, radioactive Iodine was found leaking from an exhaust pipe by a government inspector, the leak began between Tuesday and Wednesday and was confirmed to have stopped by Thursday night. The amount of radioactivity released into the air was about 402 million Becquerels (402 MBq).^[16] This was said to have been one 10 millionth of the legal limit.^[17] It is estimated that this caused an unintentional dose of 0.0002 nanosieverts (nSv), per person (i.e. average rate is 0.2 nSv (nanosieverts) per person per year). The limit for dose to the public from the operations of a nuclear plant in Japan in one year is 1100 nSv, for reference, the Three Mile Island accident caused a average dose of around 80 nSv to every individual living within 10 miles of the plant. In regards to the cause, Yasuhisa Shiozaki said "This is an error of not implementing the manual," because the vent should have been closed.^[18]

[edit] Other Problems

A diagram on Tepco's website[2] that shows the location and (usually) readings from the radiation detectors and an anemometer. In this image, from hours after the earthquake, all detectors show an error message.

About 400 drums containing low-level nuclear waste stored at the plant were knocked over by the aftershocks, 40 losing their lids^[19]. The number of spilled drums was previously reported as 100.

Company officials admitted on July 17 that a small amount of the radioactive materials cobalt-60, iodine, and chromium-51 had been released into the atmosphere, presumably from the containers losing their lids.

Criticisms of the company's response to the event included the time it took the company to report events and the certainty with which they were able to locate the source of various problems. Tepco's president, in fact, made a comment the site was a "mess"^[20] after visiting post-quake. The exact amount of leaked radioactivity remained a moving target for some time, and drew its share of criticism. After the quake, Tepco was supposedly investigating 50 separate cases of "malfunctioning and trouble,"^[21] a number that was changed to 63 cases later.^[22] Even the radioactivity sensors around the site encountered trouble, the reading from these devices are normally available online, giving the public a direct measure of ambient radioactivity around the site, but due to damage sustained during the earthquake, stopped reporting on the website. The company published an apology on that page, and data from the devices during the off-line was released later, showing no artificial abnormalities (note that the readings naturally fluctuate depending on whether it's raining or snowing and a host of other factors).^[23]

Tepco's president still maintained that fears of a radiation leak were unfounded (ie the amount leaked into the ocean increased by 50% but were still a billionth of the legal limit), but many reporters of the international community expressed distrust of the company that has had a history of cover-up controversies. The IAEA's Mohamed ElBaradei also strongly encouraged full "transparency" throughout the investigation of the accident so that lessons learned could be applied to nuclear plants elsewhere.^[20] The IAEA also offered to do an inspection of the plant, which was initially declined. The governor of Niigata prefecture then sent a petition to Shinzo Abe. On Sunday, July 22, the NISA announced that it will allow inspectors from the United Nations to look into leaks.^[24]

[edit] Impact

News of the earthquake, combined with the fact that replacement power sources (such as oil and gas) are at record highs, caused TEPCOs stock to plummet 7.5%, the largest drop in 7 years, which amounted to around 4.4 billion USD lost in stock capitalization.^[25] This made the event even more costly to the company than the 2002 data falsification scandal. Additionally, Tepco warned that the plant closure could cause a power shortage during the summer months.^[21] Trade minister Akira Amari has even requested that business users cut electricity use.^[26]

Reports of the leak caused thousands of cancellations at resorts and hotels along the Sea of Japan coast, even as far as Murakami, Niigata (140 km northeast) and Sado Island. Inn owners have said that rumors have been more damaging than direct effects of the earthquake.^[27]

[edit] 1,000,000 Volt Electric Line

There had been plans to supply some areas by means of a 1,000,000 V power line, however, objections from the local community due to concerns of electromagnetic waves stopped the plan. This would have been Japan's first electric line of that scale.

[edit] Events

By Japanese law (though 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. All reported events are public

• 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 did a power reduction, and the condenser pressure stabilized so the unit was ran 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 minuscule radioactive releases (see previous section).

[edit] References

[edit] External links

• Tokyo Electric Company Official Site for Kashiwazaki-Kariwa 東京電力・柏崎刈羽原子力発電所 (Japanese)
• Full account of problems by unit after the Niigata earthquake c/o TEPCO (Japanese)
  • Another account of the consequences of the earthquake (English)
• List of events at the plant (English)

• Maps and aerial photos for 37°25′35″N 138°35′40″E / 37.426389, 138.594444Coordinates: 37°25′35″N 138°35′40″E / 37.426389, 138.594444
  • WikiSatellite view at WikiMapia
  • City map from Multimap
  • Aerial view from GlobalGuide