Fukushima Daiichi Nuclear Power Plant

Fukushima Daiichi Nuclear Power Plant
Fukushima-1.JPG
The Fukushima Daiichi Nuclear Power Plant in 2002
CountryJapan
LocationŌkuma, Fukushima
Coordinates37°25′23″N 141°01′59″E / 37°25′23″N 141°01′59″E / 37.42306; 141.03306

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.

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]

Unit[24] Type[25]
(Containment)
Net power[26] Start construction[26] First criticality[26] Commercial operation[26] Shutdown[26] NSSS[25] A-E[7] Builder[7]
1 BWR-3
(Mark I)
439 MW July 25, 1967 October 10, 1970 March 26, 1971 May 19, 2011 General Electric Ebasco Kajima
2 BWR-4
(Mark I)
760 MW June 9, 1969 May 10, 1973 July 18, 1974 May 19, 2011 General Electric Ebasco Kajima
3 BWR-4
(Mark I)
760 MW December 28, 1970 September 6, 1974 March 27, 1976 May 19, 2011 Toshiba Toshiba Kajima
4 BWR-4
(Mark I)
760 MW February 12, 1973 January 28, 1978 October 12, 1978 May 19, 2011 Hitachi Hitachi Kajima
5 BWR-4
(Mark I)
760 MW May 22, 1972 August 26, 1977 April 18, 1978 December 17, 2013 Toshiba Toshiba Kajima
6 BWR-5
(Mark II)
1067 MW October 26, 1973 March 9, 1979 October 24, 1979 December 17, 2013 General Electric Ebasco Kajima
7 (planned) ABWR 1380 MW Canceled 04/2011 Planned 10/2016
8 (planned) ABWR 1380 MW Canceled 04/2011 Planned 10/2017

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
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