Kashiwazaki-Kariwa Nuclear Power Plant


The Kashiwazaki-Kariwa Nuclear Power Plant is a large, modern nuclear power plant on a site including land in the towns of Kashiwazaki and Kariwa in Niigata Prefecture, Japan on the coast of the Sea of Japan, from where it gets cooling water. The plant is owned and operated by Tokyo Electric Power Company.
It is the largest nuclear generating station in the world by net electrical power rating.
It was approximately from the epicenter of the second-strongest earthquake to 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 plant was completely shut down for 21 months following the earthquake. Unit 7 was restarted after seismic upgrades on May 9, 2009, followed later by units 1, 5, and 6..
After the March 11, 2011 earthquake, all restarted units were shut down and safety improvements are being carried out., no units have been restarted and the date for resuming operations remains unknown.

Reactors

There are seven units, all lined up along the coast line. Numbering starts at Unit 1 with the south-most unit through Unit 4, then there is a large green space in between Unit 4 and 7, then it continues with Units 6 and 5, the newest of the reactors.
KK – 1KK – 2KK – 3KK – 4KK – 5KK – 6KK – 7
Reactor TypeBWRBWRBWRBWRBWRABWRABWR
Net Power 1,0671,0671,0671,0671,0671,3151,315
Gross Power 1,1001,1001,1001,1001,1001,3561,356
Start of Construction5/6/198018/11/19857/3/19895/3/199020/6/19853/11/19921/7/1993
First Criticality12/12/198430/11/198919/10/19921/11/199320/7/198918/12/19951/11/1996
Commission date18/9/198528/9/199011/8/199311/8/199410/4/19907/11/19962/7/1997
Installation Costs
330360310310420310280
Reactor/NSSS SupplierToshibaToshibaToshibaHitachiHitachiHitachi/
Toshiba/GE		Hitachi/
Toshiba/GE

The power installation costs for units at this site well reflect the general trend in costs of nuclear plants. Capital costs increased through the 1980s but have become cheaper in modern times. The last two units were the first Advanced Boiling Water Reactors ever built.

Performance

Such a large plant size has several economic advantages, one of these being the limited impact of refueling outages of individual units on the plant's total net power production. A smooth transition was seen in the power production history of the plant up through the time the last two units were built. Unfortunately, since completion of construction, the plant has seen two events that caused the entire plant to be shut down.
YearUnit 1Unit 2Unit 3Unit 4Unit 5Unit 6Unit 7Total
19854.9604.960
19866.7046.704
19879.1959.195
19886.9606.960
19896.4421.0417.484
19905.9875.3867.91119.284
19919.0326.6427.09322.767
19926.9589.0470.0536.97723.035
19936.8747.2136.4880.0129.23829.825
19947.0207.2917.2646.0407.15534.771
19959.2357.6979.2546.1827.50839.877
19966.8148.8117.9228.0687.9065.6630.05845.242
19977.9007.2848.0167.5178.91910.1618.12857.926
19986.1768.1426.7489.2597.35310.7029.71658.095
19999.1998.2099.0288.1427.7729.7108.44560.505
20007.7158.1407.9456.9197.0439.41211.24058.413
20017.0717.5956.9865.5919.1999.27010.07855.790
20025.9065.8665.5769.2408.19111.5047.99054.273
20030.0000.0000.0004.1861.5038.4015.77819.869
20046.4974.6606.5505.6246.1358.63510.80548.906
20053.1266.3886.0627.1926.85311.1267.97748.725
20066.2999.3317.3312.8178.4008.4478.16650.792
20073.1651.8305.0545.0610.03.7586.35825.226
20080.00.00.00.00.00.00.00.0
20090.00.00.00.00.03.6545.3669.02
20105.2910.00.00.00.7809.5229.03424.627
20115.6060.00.00.09.40210.9607.34933.317
20120.00.00.00.00.00.00.00.0
20130.00.00.00.00.00.00.00.0
20140.00.00.00.00.00.00.00.0
20150.00.00.00.00.00.00.00.0
20160.00.00.00.00.00.00.00.0

Partial shutdowns

In February 1991, unit 2 was automatically shut down following a sudden drop in oil pressure inside the steam turbine.
On 18 July 1997, radioactive steam leaked from a gauge within unit 7 of the Kashiwazaki kariwa plant. In May a burst tube had delayed trial runs at the plant, and earlier in July smoke had been found coming from plant machinery.
In January 1998, unit 1 was shut down after increasing radiation levels in the steam driving the turbine triggered alarms. The levels were reportedly 270 times the expected operating level.
The reactors at the KK plant were shut down one by one after the discovery in 2002 of
deliberate falsification of data. The first one was taken offline September 9, 2002, and the last one was taken offline January 27, 2003. 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 during the fiscal year of 2003.

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 Japanese 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.

Earthquakes

Earthquake resistant design features

Sand at the sites was removed and the reactor was built on firm ground. Adjacent soil was backfilled. Basements of the reactor buildings extend several levels down. These underground elements stabilize the reactor buildings, making them less likely to suffer sway due to resonance vibrations during an earthquake. As with other Japanese power plants, reactors at the plant were built according to earthquake-resistance standards, which are regulated by law and the JAEC.
In 2006 safety standards for earthquake resistance in Japan's nuclear plants were modified and tightened. After the 2007 earthquake suspicions arose that another fault line may be closer to the plant than originally thought, possibly running straight through the site.

2007 Chūetsu offshore earthquake

The KK plant was 19 kilometers away from the epicenter of the magnitude 6.6 2007 Chūetsu offshore earthquake, which took place 10:13 a.m., July 16, 2007. Shaking of 6.8 m/s2 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. Units 5 and 6 also recorded shaking over this limit. Shaking of 20.58 m/s2 was recorded in the turbine building of Unit 3.
Those nearby saw black smoke which was later confirmed to be an electric transformer that had caught fire at Unit 3. The fire was put out by noon on the day of the quake, about 2 hours after it started. The 3-story transformer building was extensively charred.
Reactor units 3, 4, and 7 all automatically powered down safely in response to the quake. Unit 2 was in startup mode and not online. Units 1, 5, and 6 were already shut down for inspection at the time. TEPCO was ready to restart some of the units as of the next day, but the trade ministry ordered 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 until its safety could be confirmed. The Nikkei reported that government safety checks could delay the restart for over a year, without stating the source of the information. For comparison, in 2005, a reactor at the Onagawa NPP was closed for five months following an earthquake.

IAEA inspections

The International Atomic Energy Agency offered to inspect the plant, which was initially declined. The governor of Niigata prefecture then sent a petition to Shinzo Abe. On Sunday, July 22, 2007, the NISA announced that it would allow inspectors from the United Nations to review the damage.
A team from the IAEA carried out a four-day inspection, as investigations by Japan's Nuclear and Industrial Safety Agency, Nuclear Safety Commission and the Tokyo Electric Power Company continued. The team of the IAEA confirmed that the plant had "shut down safely" and that "damage appears less than expected." On August 19, the IAEA reported that, for safety-related and nuclear components, "no visible significant damage has been found" although "nonsafety related structures, systems and components were affected by significant damage".
The official report issued by the IAEA stated that the plant "behaved in a safe manner" after a 4-day inspection. Other observations were:
Recommendations included:
External inspections of the plant were planned to be completed by the end of July 2008. The schedule was confirmed on 10 July 2008 by the site superintendent, Akio Takahashi. On July 15, Akira Amari said his ministry was also continuing their own tests. An IAEA workshop in June 2008 recognized that the earthquake exceeded the "seismic input" used in the design in that plant, and that regulations played a critical role in keeping the plant safe. However, TEPCO determined that significant upgrades were required to cope with the improved understanding of the seismic environment and possible shaking effects at the plant site.
The IAEA sent a team for a follow-up visit in January 2008. They concluded that much high-quality inspection work had been undertaken and noted the likely improvements to nuclear seismic design worldwide that may result from this process. An additional visit from an IAEA team of 10 experts occurred in December 2008, noting that the "unexpectedly large ground motions" were now well understood and could be protected against, and further confirming the safe performance of the plant during the quake.

Radioactivity releases

Initially, it was thought that some water from the spent fuel pool leaked into the Sea of Japan as a result of the quake. 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 NISA, this was the first time a release of radioactive material happened as a result of an earthquake.
About 400 drums containing low-level nuclear waste stored at the plant were knocked over by the aftershocks, 40 losing their lids. Company officials reported on July 17 that traces 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 made a comment the site was a "mess" after visiting post-quake. While the reported amount of leaked radioactivity remained far below what poses a danger to the public, details changed multiple times in the few days after the quake and attracted significant media attention. After the quake, TEPCO was supposedly investigating 50 separate cases of "malfunctioning and trouble," a number that was changed to 63 cases later. 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 covering the off-line period was released later, showing no artificial abnormalities.
TEPCO's president maintained that fears of a leak of radioactive material were unfounded, but many international reporters expressed distrust of the company that has a history of cover-up controversies. The IAEA's Mohamed ElBaradei encouraged full transparency throughout the investigation of the accident so that lessons learned could be applied to nuclear plants elsewhere.

Impact

News of the earthquake, combined with the fact that replacement power sources are at record highs, caused TEPCOs stock to plummet 7.5%, the largest drop in seven years, which amounted to around US$4.4 billion lost in stock capitalization. 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. Trade minister Akira Amari requested that business users cut electricity use, and in August TEPCO was forced to reduce electricity supplies for industrial uses, the first time it had to resort to such measures in 17 years.
Reports of the leak caused thousands of cancellations at resorts and hotels along the Sea of Japan coast, even as far as Murakami, Niigata and Sado Island. Inn owners have said that rumors have been more damaging than direct effects of the earthquake.
The shutdown forced TEPCO to run natural gas plants in place of this plant, not only increasing Japan's demand for the fuel and increasing the price internationally, but also increasing carbon dioxide output such that Japan will have difficulty meeting the Kyoto Protocol.

Restart

After 16 months of comprehensive component-based assessment and upgrades on all seven reactors, this phase of post-earthquake response was almost complete, with reactor 7 fully upgraded to cope with the seismic environment. On 8 November 2008, fuel loading in reactor unit 7 started, preparatory to a period of system safety tests on that reactor. On 19 February 2009 TEPCO applied to the local governance to restart unit 7 after having obtained approval from the national government and regulators. Local government agreement for restart was granted in May and electrical grid power was supplied from Unit 7 at 20% power on 19 May. The reactor was raised to 100% power on 5 June 2009 as part of a series of restart tests.
Unit 6 restarted on 26 August 2009 and reconnected to the grid on 31 August.
Unit 1 restarted on 31 May 2010 after loading with fuel earlier in the year, and was generating grid power by 6 June 2010.
Unit 5 recommenced grid generation on 26 November 2010, in the same week that fuel loading for unit 3 started.

2011 Tōhoku earthquake

The plant was not affected by the 11 March 2011 Tōhoku earthquake and tsunami. Subsequently, reactors were shut down for scheduled inspections and local governors and courts would not allow them to be restarted.

Facility improvements after Fukushima I nuclear accidents

On 21 April 2011, after the Fukushima Daiichi nuclear disaster, TEPCO announced a plan to build up the seawall to a height of 15 m above sea level and spanning more than 800 m in length for units 1–4, and more than 500 m for units 5–7 by June 2013. The height of a potential tsunami was assumed to be 3.3 m. Also, plans were made to rebuild the radioactive overflow storage pool to be completed by September 2012.

2011–2012: Survey on tsunamis in the past

On 10 November 2011, TEPCO announced a survey for signs of past tsunamis in this area. With drills, soil samples were to be taken of sediment layers dating from the year 1600 back to 7000 years ago, at nine locations around the plant at the coast of central Japan. This survey, the first that TEPCO ever conducted on this subject, did start on 15 November 2011, and was planned to be completed in April 2012, and was done to examine the possibility of higher tsunamis than had been expected at the time the plant was designed and built.
On 26 April 2012, TEPCO said that it would recalculate the risks of earthquakes and tsunamis. This was done after reports, as published by four prefectures around the nuclear Plant, re-estimated the risks of potential earthquakes in the region:
The calculated earthquake magnitudes are almost three times stronger than all the calculations done by TEPCO regarding the safety assessments for the plant. These were based on a magnitude 7.85 quake caused by a 131 kilometer long fault near Sado Island in Niigata and a 3.3 meter-high tsunami. To endure this, an embankment was under construction to resist tsunami waves up to 15 meters high. The recalculation could have consequences for the stress tests and safety assessments for the plant.
After the planned revision of the safety standards in July 2013, some faults under the reactors were considered as geologically active. This was found by a Japanese newsagency Kyodo News on 23 January 2013 in papers and other material published by TEPCO. Under the new regulations, geologic faults would be considered to be active if they had moved within the last 400 000 years, instead of the less stringent standard of 120 000 years, as was formerly accepted. Two faults, named "Alpha" and "Beta," are present under Reactors 1 and 2. Other faults are situated under Reactor 3 and Reactor 5, as well as underneath the building of Reactor 4. Under the new regulations, the beta-fault could be classified as active because it moved a ground layer including volcanic ash around 240 000 years ago. The final outcome of the study might trigger a second survey by the newly installed Japanese regulator NRA. In January 2013, studies were conducted or planned on geological faults around six Japanese reactor sites. The Kashiwazaki-Kariwa plant would be number 7.

Niigata Chuetsu Offshore earthquake