Kashiwazaki Kariwa Nuclear Power Plant

Updated on Oct 29, 2023

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Country Japan Cooling source Sea of Japan Opened 18 September 1985 Construction began 5 June 1980		Status Out of service Cooling towers no Phone +81 257-45-3131

Commission date September 18, 1985 (1985-09-18) Operator(s) Tokyo Electric Power Company Address Japan, 〒945-0016 Niigata Prefecture, Kashiwazaki, 青山町１６−４６ Similar Fukushima Daini Nuclear P, Hamaoka Nuclear Power Pl, Onagawa Nuclear Power Pl, Advanced boiling water rea, Takahama Nuclear Power Pl

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 first ABWR) nuclear power plant on a 4.2-square-kilometer (1,038 acres) 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 (TEPCO).

It was the largest nuclear generating station in the world by net electrical power rating.

It was approximately 19 km (12 mi) from the epicenter of the second strongest earthquake to ever occur at a nuclear plant, the M_w 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. (Units 2, 3, 4 were not restarted).

After the April 2011 earthquake, all restarted units were shut down and safety improvements are being carried out. As of December 2016 no units are restarted and no units are expected to restart sooner than in 2017.

Reactors

There are seven units, which are 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.

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 (ABWRs) 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.

2002 shut downs

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. 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.

1998 shut down

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.

1997 minor problems

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.

1991 shut down

In February 1991, unit 2 was automatically shut down following a sudden drop in oil pressure inside the steam turbine.

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 (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.

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 (maximum of 42 m below grade). 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.

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 operating 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.

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 (0.69 g) 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 (NISA), Nuclear Safety Commission (NSC) and the Tokyo Electric Power Company (TEPCO) 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:

"Safety related structures, systems and components of the plant seem to be in a general condition, much better than might be expected for such a strong earthquake, and there is no visible significant damage"

Conservatisms introduced in the construction of the plant compensated for the magnitude of the earthquake being so much greater than planned for.

Recommendations included:

A re-evaluation of the seismic safety.

Detailed geophysical investigations

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 (estimated to be about 1.5 L) 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.

0.6 litres of slightly radioactive water leaked from the third floor of the Unit 6 reactor building, which contained 280 becquerels of radioactivity. (For reference, a household smoke detector typically contains 37,000 becquerels (1.0 µCi) of radioactivity, and a living adult human typically has around 8000 Bq of naturally occurring radioactivity inside his or her body.)

0.9 litres of slightly radioactive water leaked from the inner third floor of the Unit 6 reactor building, containing 16,000 Bq of radioactivity.

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. For comparison, 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.

On Wednesday, 18 July 2007, 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 iodine released was estimated at 12 million Bq and the total amount of particulate radioactivity released into the air was about 402,000,000 Bq. This was said to have been one 10 millionth of the legal limit. It is estimated that this caused an unintentional dose of 0.0002 nanosieverts (nSv), per person distributed among around 10 million people. The limit for dose to the public from the operations of a nuclear plant in Japan in one year is 1100 nSv, and, for comparison, natural background radiation worldwide for humans is on average around 2,400,000 nSv/year (2.4 mSv/year). In regards to the cause, Yasuhisa Shiozaki said "This is an error of not implementing the manual," because the vent should have been closed.

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 seven years, which amounted to around 4.4 billion USD 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 (140 km northeast) 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 (along with Unit 5) 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 (see Events below) and local governors and courts would not allow them to be restarted.

Facility improvements after Fukushima I nuclear accidents

After Fukushima Daiichi nuclear disaster, TEPCO announced on 21 April 2011, the plan to build up the seawall, to a height of 15 m (49.2 ft) above sea level, more than 800 m (2,624 ft) in length for units 1- 4, and more than 500 m (1,640 ft) for unit 5-7 by June 2013, which has been assumed 3.3 m height of tsunami. Also, plans have been made to rebuild the storage pool for radioactive water overflow 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:

Tottori Prefecture: a 220 kilometer long fault might trigger an 8.15 magnitude earthquake

Shimane Prefecture : 8.01 magnitude

Ishikawa Prefecture : 7.99 magnitude

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.

Events

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.

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.

On August 5, 2011, 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.

On 22 August 2011 reactor 7 was taken offline for regular inspections. The normal time for this checkup was about 3 months.

On 9 September 2011 TEPCO started with stress-tests to confirm the safety of two of its idle nuclear reactors. A computer-simulation was to be used to confirm the reactors' earthquake and tsunami resistance. This test was introduced after the triple meltdown at the Fukushima-accident. All reactors in Japan needed to pass this test after their normal regular inspections before they were allowed to resume operation. The Governor of Niigata Hirohiko Izumida said that he would not take any decision about a restart before the Fukushima accident would be properly assessed.

On 12 July 2012, in order to block all attempts to reactivate any nuclear reactor of the Kashiwazaki-Kariwa nuclear plant, three plaintiffs, including two nuclear crisis evacuees, demanded during the first oral proceedings of a lawsuit at the Niigata District court, that the plant should be closed for ever. The lawsuit was filed by 132 people from six prefectures, among them 13 evacuees from Fukushima Prefecture. TEPCO asked the court in a written reply to reject the case. Tha plaintiffs agued that the disaster in Fukushima, that contaminated their hometowns, was described as "man-made". According to them, nuclear plants, which could cause unpredictable damage, should not be constructed, and "(TEPCO) should realize that it is going to pass this bitter legacy on to the future." They argued also, that TEPCO had neither the qualifications nor capability to operate and manage nuclear plants, and that the Kashiwazaki-Kariwa nuclear plant was "built in an extremely dangerous place." The lawsuit was the first that tried to shut down a nuclear reactor operated by TEPCO since the disaster at the Fukushima Daiichi plant in 2011.

On 2 July 2013 TEPCO announced that it would ask the nuclear regulatory authority permission to restart reactors 6 and 7 after the new safety regulations would take effect on 8 July 2013. Before approval could be obtained the NRA did need to confirm that the plant satisfied the new safety regulations. TEPCO would try to explain the request to the government of the Niiagata prefecture, but it could be difficult to convince governor Hirohiko Izumida. By restarting the nuclear plant TEPCO hoped to cut its spending on fossil fuel.

References

Kashiwazaki-Kariwa Nuclear Power Plant Wikipedia

(Text) CC BY-SA