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Fukushima Daiichi Nuclear Power Plant
The Fukushima Daiichi Nuclear Power Plant in 2002
Country	Japan
Location	Ōkuma, Fukushima
Coordinates	37°25′23″N 141°01′59″E / 37.42306°N 141.03306°E / 37.42306; 141.03306Coordinates: 37°25′23″N 141°01′59″E / 37.42306°N 141.03306°E / 37.42306; 141.03306
Status	Being decommissioned
Construction began	July 25, 1967 (1967-07-25)
Commission date	March 26, 1971 (1971-03-26)
Operator(s)	Tokyo Electric Power Company
Nuclear power station
Reactor type	BWR
Reactor supplier	General Electric Toshiba Hitachi
Power generation
Units decommissioned	1 × 460 MWe (Unit 1 damaged) 4 × 784 MWe (Units 2, 3, and 4 damaged; Unit 5 slightly damaged) 1 × 1100 MWe (unit 6 slightly damaged)
Website http://www.tepco.co.jp/en/nu/press/f1-np/index-e.html

The Fukushima Daiichi Nuclear Power Plant (福島第一原子力発電所, Fukushima Daiichi Genshiryoku Hatsudensho) is a disabled nuclear power plant located on a 3.5-square-kilometre (860-acre) site^[1] in the towns of Ōkuma and Futaba in the Fukushima Prefecture, Japan. The plant suffered major damage from the magnitude 9.0 earthquake and tsunami that hit Japan on March 11, 2011. The chain of events caused radiation leaks, and permanently damaged several reactors making them impossible to restart. By political decision, the remaining reactors were not restarted.

First commissioned in 1971, the plant consists of six boiling water reactors. These light water reactors^[2] drove electrical generators with a combined power of 4.7 GWe, making Fukushima Daiichi one of the 15 largest nuclear power stations in the world. Fukushima was the first nuclear plant to be designed, constructed and run in conjunction with General Electric and Tokyo Electric Power Company (TEPCO).^[3]

The March 2011 disaster disabled the reactor cooling systems, leading to releases of radioactivity and triggering a 30 km evacuation zone surrounding the plant; the releases continue to this day. On April 20, 2011, the Japanese authorities declared the 20 km evacuation zone a no-go area which may only be entered under government supervision.

In April 2012, Units 1-4 were decommissioned. Units 2-4 were decommissioned on April 19, while Unit 1 was the last of these four units to be decommissioned on April 20 at midnight.^{[citation needed]} In December 2013 TEPCO decided none of the undamaged units will reopen.

The sister nuclear plant Fukushima Daini ("number two"), 12 km (7.5 mi) to the south, is also run by TEPCO. It also suffered serious damages during the tsunami, especially at the seawater intakes of all four units, but could be shut down and brought to a safe state through extraordinary actions^{[clarification needed]} by the plant crew.^[4]

Power plant information

Cross-section sketch of a typical BWR Mark I containment, as used in Units 1 to 5. The reactor core (1) consists of fuel rods and control rods (39) which are moved in and out by the device (31). Around the pressure vessel (8), there is an outer containment (19) which is closed by a concrete plug (2). When fuel rods are moved in or out, the crane (26) will move this plug to the pool for facilities (3). Steam from the dry well (11) can move to the wet well (24) through jet nozzles (14) to condense there (18). In the spent fuel pool (5), the used fuel rods (27) are stored.

The reactors for Units 1, 2, and 6 were supplied by General Electric, those for Units 3 and 5 by Toshiba, and Unit 4 by Hitachi. All six reactors were designed by General Electric.^[5][6] Architectural design for General Electric's units was done by Ebasco. All construction was done by Kajima.^[7] Since September 2010, Unit 3 has been fueled by a small fraction (6%)^[8] of plutonium containing mixed-oxide (MOX) fuel, rather than the low enriched uranium (LEU) used in the other reactors.^[9][10] Units 1–5 were built with Mark I type (light bulb torus) containment structures.^[11][12] The Mark I containment structure was slightly increased in volume by Japanese engineers.^[13] Unit 6 has a Mark II type (over/under) containment structure.^[11][12][14]

Unit 1 is a 460 MW boiling water reactor (BWR-3) constructed in July 1967. It commenced commercial electrical production on March 26, 1971, and was initially scheduled for shutdown in early 2011.^[15] In February 2011, Japanese regulators granted an extension of ten years for the continued operation of the reactor.^[16] It was damaged during the 2011 Tōhoku earthquake and tsunami.^[17]

Unit 1 was designed for a peak ground acceleration of 0.18 g (1.74 m/s²) and a response spectrum based on the 1952 Kern County earthquake, but rated for 0.498 g.^[11][18] The design basis for Units 3 and 6 were 0.45 g (4.41 m/s²) and 0.46 g (4.48 m/s²) respectively.^[19] All units were inspected after the 1978 Miyagi earthquake when the ground acceleration was 0.125 g (1.22 m/s²) for 30 seconds, but no damage to the critical parts of the reactor was discovered.^[11] The design basis for tsunamis was 5.7 meters.^[20]

The reactor's emergency diesel generators and DC batteries, crucial components in helping keep the reactors cool in the event of a power loss, were located in the basements of the reactor turbine buildings. The reactor design plans provided by General Electric specified placing the generators and batteries in that location, but mid-level engineers working on the construction of the plant were concerned that this made the backup power systems vulnerable to flooding. TEPCO elected to strictly follow General Electric's design in the construction of the reactors.^[21]

Site layout

Aerial view of the plant area in 1975, showing separation between Units 5 & 6, and the majority of the complex
・Unit 6: direction of Sōma
・Unit 4: direction of Iwaki

The plant is on a bluff which was originally 35 meters above sea level. During construction, however, TEPCO lowered the height of the bluff by 25 meters. One reason for lowering the bluff was to allow the base of the reactors to be constructed on solid bedrock in order to mitigate the threat posed by earthquakes. Another reason was the lowered height would keep the running costs of the seawater pumps low. TEPCO's analysis of the tsunami risk when planning the site's construction determined that the lower elevation was safe because the sea wall would provide adequate protection for the maximum tsunami assumed by the design basis. However, the lower site elevation did increase the vulnerability for a tsunami larger than anticipated in design.^[22]

The Fukushima Daiichi site is divided into two reactor groups, the leftmost group - when viewing from the ocean - contains units 4, 3, 2 and 1 going from left to right. The rightmost group - when viewing from the ocean - contains the newer units 5 and 6, respectively, the positions from left to right. A set of seawalls protrude into the ocean, with the water intake in the middle and water discharge outlets on either side.

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  Aerial view of the Fukushima I plant area in 1975, showing sea walls and completed reactors
  

  
  

  
  


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  Closeup of Units 4, 3, 2 and 1
  

  
  

  
  


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  Major buildings
  

  
  

  
  


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  Illustration of post-accident state of 1–4 reactors, all but 2 display obvious damage to secondary containment
  

  
  

  
  

Reactor data

Units 7 and 8 were planned to start construction in April 2012 and 2013 and to come into operation in October 2016 and 2017 respectively. The project was formally canceled by TEPCO in April 2011 after local authorities questioned the fact that they were still included in the supply plan for 2011, released in March 2011, after the accidents. The company stated that the plan had been drafted before the earthquake.^[23]

Electrical connections

The Fukushima Daiichi plant is connected to the power grid by four lines, the 500 kV Futaba Line (双葉線), the two 275 kV Ōkuma Lines (大熊線) and the 66 kV Yonomori Line (夜の森線) to the Shin-Fukushima (New Fukushima) substation.

The Shin-Fukushima substation also connects to the Fukushima Daini plant by the Tomioka Line (富岡線). Its major connection to the north is the Iwaki Line (いわき幹線), which is owned by Tohoku Electric Power. It has two connections to the south-west that connect it to the Shin-Iwaki substation (新いわき).

Operating history

Plant still under construction circa 1971

The plant reactors came online one at a time beginning in 1970 and the last in 1979. From the end of 2002 through 2005, the reactors were among those shut down for a time for safety checks due to the TEPCO data falsification scandal.^[27][28] On February 28, 2011, TEPCO submitted a report to the Japanese Nuclear and Industrial Safety Agency admitting that the company had previously submitted fake inspection and repair reports. The report revealed that TEPCO failed to inspect more than 30 technical components of the six reactors, including power boards for the reactor's temperature control valves, as well as components of cooling systems such as water pump motors and emergency power diesel generators.^[29] In 2008, the IAEA warned Japan that the Fukushima plant was built using outdated safety guidelines, and could be a "serious problem" during a large earthquake.^[30] The warning led to the building of an emergency response center in 2010, used during the response to the 2011 nuclear accident.^[30][31]

On April 5, 2011, TEPCO vice president Takashi Fujimoto announced that the company was canceling plans to build Reactors No. 7 and 8.^[32][33] On May 20 TEPCO's board of directors' officially voted to decommission Units 1 through 4 of the Fukushima Daiichi nuclear power plant and to cancel plans to build units 7 and 8. It refused however to make a decision regarding units 5 and 6 of the station or units 1 to 4 of the Fukushima Daini nuclear power station until a detailed investigation is made. In December 2013 TEPCO decided to decommission the undamaged units 5 and 6; they may be used to test remote clean-up methods before use on the damaged reactors.^[34]

Electricity generation for the Fukushima I NPP by Unit in GW·h^[26]

Electricity generation for the Fukushima I

Year	Unit 1	Unit 2	Unit 3	Unit 4	Unit 5	Unit 6
1970	60.482
1971	2024.3
1972	2589.1
1973	2216.8	5.949
1974	1629.7	3670.1	284.7
1975	0	622.1	2961.8
1976	1563.9	4191.4	4807.1
1977	0	49.7	2171.1		875.1
1978	1497.6	3876.3	2753.7	3163.2	4806.7
1979	2504.4	2976	4916.3	3917.4	3898.6	3235.6
1980	1249.5	2889	4287	4317	4282.6	6441.1
1981	1084.8	3841.8	3722.8	4667.5	4553.9	7418.6
1982	2355	5290.2	2886.8	5734.7	4061.3	6666.5
1983	3019.5	3422.7	4034	4818.2	5338.8	5387.8
1984	2669.761	3698.718	4497.326	4433.166	4691.482	5933.242
1985	1699.287	4266.285	5798.641	4409.031	4112.429	5384.802
1986	2524.683	5541.101	4234.196	4315.241	4157.361	7783.537
1987	3308.888	3851.078	3748.839	5964.048	3995.012	7789.201
1988	2794.464	4101.251	5122.991	5309.892	5952.712	5593.058
1989	1440.778	6516.393	5706.694	4232.648	4766.535	5128.362
1990	2352.405	3122.761	2919.548	4273.767	3956.549	7727.073
1991	1279.986	3853.054	4491.022	6483.384	6575.818	6948.662
1992	1794.061	4568.531	6098.742	4082.747	4841.234	5213.607
1993	2500.668	4186.704	4204.301	4206.577	4059.685	6530.932
1994	3337.532	2265.961	4202.304	6323.277	4246.206	8079.391
1995	3030.829	6396.469	5966.533	5485.662	5878.681	6850.839
1996	2298.589	5192.318	4909.655	4949.891	5666.866	6157.765
1997	3258.913	4618.869	2516.651	4556.81	4609.382	9307.735
1998	3287.231	3976.16	2632.682	5441.398	5369.912	6328.985
1999	2556.93	3158.382	5116.09	5890.548	6154.135	7960.491
2000	3706.281	5167.247	5932.485	4415.901	1647.027	7495.577
2001	487.504	5996.521	5637.317	5858.452	5905.13	7778.874
2002	3120.2	5101.018	3567.314	4687.718	6590.488	6270.918
2003	0	1601.108	2483.557	0	2723.76	4623.905
2004	0	3671.49	3969.674	4728.987	5471.325	1088.787
2005	851.328	3424.939	5103.85	1515.596	2792.561	7986.451
2006	3714.606	3219.494	4081.932	4811.409	4656.9	5321.767
2007	610.761	5879.862	4312.845	5050.607	5389.565	6833.522
2008	3036.562	5289.599	6668.839	4410.285	3930.677	8424.526
2009	2637.414	4903.293	4037.601	5462.108	5720.079	7130.99
2010	2089.015			6040.782

Warnings and design critique

In 1990, the U.S. Nuclear Regulatory Commission (NRC) ranked the failure of the emergency electricity generators and subsequent failure of the cooling systems of plants in seismically very active regions one of the most likely risks. The Japanese Nuclear and Industrial Safety Agency (NISA) cited this report in 2004. According to Jun Tateno, a former NISA scientist, TEPCO did not react to these warnings and did not respond with any measures.^[35]

Filmmaker Adam Curtis mentioned the risks of the type of boiling water reactors cooling systems such as those in Fukushima I,^[36] and claimed the risks were known since 1971^[37] in a series of documentaries in the BBC in 1992 and advised that PWR type reactors should have been used.

TEPCO, that operated the station, had been warned their seawall was insufficient to withstand a powerful tsunami, but the seawall height was not increased in response. While other stations run by the Tohoku Electric Power company had much more robust seawalls (such as the Onagawa Nuclear Power Plant) down the coast closer to the epicenter of the earthquake, the Fukushima Plant did not.

Incidents and accidents

Prior to March 2011

1978

Fuel rods fell in reactor No. 3, causing a nuclear reaction.^[38] It took about seven and a half hours to place the rods back into proper positions.^[39]

February 25, 2009

A manual shutdown was initiated during the middle of a start-up operation. The cause was a high pressure alarm that was caused by the shutting of a turbine bypass valve. The reactor was at 12% of full power when the alarm occurred at 4:03 am (local time) due to a pressure increase to 1,030 psi (7,100 kPa), exceeding the regulatory limit of 1,002 psi (6,910 kPa). The reactor was reduced to 0% power, which exceeded the 5% threshold that requires event reporting, and pressure dropped back under the regulatory limit at 4:25 am. Later, at 8:49 am the control blades were completely inserted, constituting a manual reactor shutdown. An inspection then confirmed that one of the 8 bypass valves had closed and that the valve had a bad driving fluid connection. The reactor had been starting up following its 25th regular inspection, which had begun on October 18, 2008.^[40]

March 26, 2009

Unit 3 had problems with over-insertion of control blades during outage. Repair work was being done on equipment that regulates the driving pressure for the control blades, and when a valve was opened at 2:23 pm a control blade drift alarm went off. On later inspection, it was found that several of the rods had been unintentionally inserted.^[41]

November 2, 2010

Unit 5 had an automatic SCRAM while an operator was conducting an adjustment to the control blade insertion pattern. The SCRAM was caused by a reactor low water level alarm. The turbine tripped along with the reactor and there was no radiation injury to workers.^[42]

Nuclear disaster of March 2011

Three of the reactors at Fukushima Daiichi overheated, causing meltdowns that eventually led to explosions, which released large amounts of radioactive material into the air.^[43]

On March 11, 2011, an earthquake categorized as 9.0 M_W on the moment magnitude scale occurred at 14:46 Japan Standard Time (JST) off the northeast coast of Japan, one of the most powerful earthquakes in history. Units 4, 5 and 6 had been "shut down" prior to the earthquake for planned maintenance.^[44][45] The remaining reactors were shut down/SCRAMed automatically after the earthquake, and the remaining decay heat of the fuel was being cooled with power from emergency generators. The subsequent destructive tsunami with waves of up to 14 meters that over-topped the station, which had seawalls, disabled emergency generators required to cool the reactors and Spent fuel pools in Units 1-5. Over the following three weeks there was evidence of partial nuclear meltdowns in units 1, 2 and 3: visible explosions, suspected to be caused by hydrogen gas, in units 1 and 3; a suspected explosion in unit 2, that may have damaged the primary containment vessel; and a possible uncovering of the Spent fuel pools in Units 1, 3 and 4.^[46] Units 5 & 6 were reported on March 19, by the station-wide alert log updates of the IAEA, to have gradually rising spent fuel pool temperatures as they had likewise lost offsite power, but onsite power provided by Unit 6's two diesel generators that had not been flooded, were configured to do double-duty and cool both Unit 5 and 6's spent fuel pools "and cores".^[47] As a precautionary measure, vents in the roofs of these two units were also made to prevent the possibility of hydrogen gas pressurization and then ignition.^[47]

Radiation releases from Units 1-4 caused large evacuations, concern about food and water supplies, and treatment of nuclear workers.^[48][49][50] Radiation releases also contaminated the 2011 harvest.

The events at units 1, 2 and 3 have been rated at Level 5 each on the International Nuclear Event Scale, and those at unit 4 as Level 3 (Serious Incident) events, with the overall plant rating at Level 7 (major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures).^[51]

After March 2011

IAEA Experts at Fukushima Daiichi Nuclear Power Plant Unit 4, 2013

April 3, 2011

2 bodies were discovered in the basement turbine room, most likely because the workers ran there during the tsunami.

April 9, 2013

Radioactive water leaked from the storage units, minimally contaminating the soil and water nearby. The leak was controlled and stored in a contained area. The stored water continues to require maintenance, until its ultimate purification.^[52]

July 9, 2013

TEPCO officials reported that radioactive caesium was 90 times higher than it was 3 days prior (July 6), and that it may spread into the Pacific Ocean. TEPCO reported that the caesium-134 levels in the well water were measured at 9 kilobecquerel per liter, 150 times the legal level, while Caesium-137 was measured at 18 kilobecquerel per liter, 200 times the permitted level.^[53]

August 7, 2013

Japanese officials said highly radioactive water was leaking from Fukushima Daiichi into the Pacific Ocean at a rate of 300 tons (about 272 metric tons) per day. Japanese Prime Minister Shinzo Abe ordered government officials to step in.^[54]

April 12, 2016

Melted reactors were being cooled down with 300 tonnes of water each day.^[55]

November 21, 2016

In November 2016, a 6.9 magnitude earthquake struck off the northeast coast of Japan, causing a 1m tsunami to hit the Fukishima plant. A cooling system for spent nuclear fuel was temporarily stopped.^{[citation needed]}

Dismantling of reactors

On August 1, 2013, the Japanese Industry Minister Toshimitsu Motegi approved the creation of a structure to develop the technologies and processes necessary to dismantle the four reactors damaged in the Fukushima accident.^[56]

See also

Wikimedia Commons has media related to Fukushima I Nuclear Power Plant.

• GE Three


• List of boiling water reactors


• List of earthquakes in Japan


• Nuclear power in Japan

2011 earthquake and tsunami accident

• Fukushima Daiichi nuclear disaster


• International reactions to the Fukushima Daiichi nuclear disaster


• Japanese reaction to Fukushima Daiichi nuclear disaster


• Radiation effects from the Fukushima Daiichi nuclear disaster

References

External links

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  Official site Tokyo Electric Company 東京電力・福島第一原子力発電所 (in Japanese)
  


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  Archived photo. Units 1–4 can be seen from left to right.


• 3D Google Earth view