The is a disabled

nuclear power plant A nuclear power plant (NPP) is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power stations, heat is used to generate steam that drives a steam turbine connected to a generator that produces ...

located on a site in the towns of Ōkuma and Futaba in

Fukushima Prefecture Fukushima Prefecture (; ja, 福島県, Fukushima-ken, ) is a prefecture of Japan located in the Tōhoku region of Honshu. Fukushima Prefecture has a population of 1,810,286 () and has a geographic area of . Fukushima Prefecture borders Miyagi ...

, 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 of its American-designed reactors, making them impossible to restart. By political decision, the remaining reactors were not restarted. First commissioned in 1971, the plant consists of six American-designed

boiling water reactor A boiling water reactor (BWR) is a type of light water nuclear reactor used for the generation of electrical power. It is a design different from a Soviet graphite-moderated RBMK. It is the second most common type of electricity-generating nu ...

s. These

light water reactor The light-water reactor (LWR) is a type of thermal-neutron reactor that uses normal water, as opposed to heavy water, as both its coolant and neutron moderator; furthermore a solid form of fissile elements is used as fuel. Thermal-neutron react ...

s 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 General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable ene ...

and

Tokyo Electric Power Company , also known as or TEPCO, is a Japanese electric utility holding company servicing Japan's Kantō region, Yamanashi Prefecture, and the eastern portion of Shizuoka Prefecture. This area includes Tokyo. Its headquarters are located in Uchisaiw ...

(TEPCO). The March 2011 disaster disabled the reactor cooling systems, leading to releases of radioactivity and triggering a evacuation zone surrounding the plant; the releases continue to this day. On April 20, 2011, the Japanese authorities declared the evacuation zone a no-go area which may only be entered under government supervision. In November 2011, the first journalists were allowed to visit the plant. They described a scene of devastation in which three of the reactor buildings were destroyed; the grounds were covered with mangled trucks, crumpled water tanks and other debris left by the tsunami; and radioactive levels were so high that visitors were only allowed to stay for a few hours. In April 2012, Units 1–4 were shut down. Units 2–4 were shut down on April 19, while Unit 1 was the last of these four units to be shut down on April 20 at midnight. In December 2013 TEPCO decided none of the undamaged units will reopen. In April 2021, the Japanese government approved the dumping of radioactive water of this power plant into the Pacific Ocean over the course of 30 years. The sister nuclear plant Fukushima Daini ( "number two"), to the south, is also run by TEPCO. It also suffered serious damage during the tsunami, especially at the seawater intakes of all four units, but was successfully shut down and brought to a safe state through extraordinary actions by the plant crew.

Power plant information

The reactors for Units 1, 2, and 6 were supplied by

, those for Units 3 and 5 by

Toshiba , commonly known as Toshiba and stylized as TOSHIBA, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan. Its diversified products and services include power, industrial and social infrastructure systems, ...

, and Unit 4 by

Hitachi () is a Japanese multinational conglomerate corporation headquartered in Chiyoda, Tokyo, Japan. It is the parent company of the Hitachi Group (''Hitachi Gurūpu'') and had formed part of the Nissan ''zaibatsu'' and later DKB Group and Fuyo G ...

. All six reactors were designed by General Electric. Architectural design for General Electric's units was done by

Ebasco Ebasco Services was a United States-based designer and constructor of energy infrastructure, most notably nuclear power plants. History The company was formed from the Electric Bond and Share Company, a holding company that sold securities of el ...

. All construction was done by

Kajima is one of the oldest and largest construction companies in Japan. Founded in 1840, the company has its headquarters in Motoakasaka, Minato, Tokyo. The company is known for its DIB-200 proposal. The company stock is traded on four leading J ...

. Since September 2010, Unit 3 has been fueled by a small fraction (6%) of

plutonium Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exh ...

containing mixed-oxide (MOX) fuel, rather than the

low enriched uranium Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (2 ...

(LEU) used in the other reactors. Units 1–5 were built with Mark I type (light bulb torus) containment structures. The Mark I containment structure was slightly increased in volume by Japanese engineers. Unit 6 has a Mark II type (over/under) containment structure. Unit 1 is a 460 MW

( BWR-3) constructed in July 1967. It commenced commercial electrical production on March 26, 1971, and was initially scheduled for shutdown in early 2011. In February 2011, Japanese regulators granted an extension of ten years for the continued operation of the reactor. It was damaged during the

2011 Tōhoku earthquake and tsunami The occurred at 14:46 Japan Standard Time, JST (05:46 UTC) on 11 March. The Moment magnitude scale, magnitude 9.0–9.1 (M) Submarine earthquake, undersea megathrust earthquake had an epicenter in the Pacific Ocean, east of the Oshika Peni ...

. Unit 1 was designed for a

peak ground acceleration Peak ground acceleration (PGA) is equal to the maximum ground acceleration that occurred during earthquake shaking at a location. PGA is equal to the amplitude of the largest absolute acceleration recorded on an accelerogram at a site during a par ...

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. 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. All units were inspected after the 1978 Miyagi earthquake when the

ground acceleration Peak ground acceleration (PGA) is equal to the maximum ground acceleration that occurred during earthquake shaking at a location. PGA is equal to the amplitude of the largest absolute acceleration recorded on an accelerogram at a site during a par ...

was 0.125 g (1.22 m/s²) for 30 seconds, but no damage to the critical parts of the reactor was discovered. The design basis for tsunamis was . 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.

Site layout

Fukushima I NPP 1975 medium crop rotated labeled

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. 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. File:Fukushima I NPP 1975.jpg, Aerial view of the Fukushima I plant area in 1975, showing sea walls and completed reactors File:Fukushima I NPP 1975 reactors 1 to 4 crop.jpg, Closeup of Units 4, 3, 2 and 1 File:Fukushima I Nuclear Powerplant site close-up (wotext).PNG, Major buildings File:Fukushima I nuclear accidents diagram.svg, 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.

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 is an electric utility, servicing 7.6 million individual and corporate customers in six prefectures in Tōhoku region plus Niigata Prefecture. It provides electricity at 100 V, 50 Hz, though some area use 60 Hz. 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

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. On February 28, 2011, TEPCO submitted a report to the Japanese

Nuclear and Industrial Safety Agency The was a Japanese nuclear regulatory and oversight branch of the Agency for Natural Resources and Energy under the Ministry of Economy, Trade and Industry (METI). It was created in 2001 during the 2001 Central Government Reform. Especially afte ...

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. 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.http://www.indianexpress.com/news/iaea-warned-japan-over-nuclear-quake-risk-wikileaks/763709/ IAEA warned Japan over nuclear quake risk: WikiLeaks The warning led to the building of an emergency response center in 2010, used during the response to the 2011 nuclear accident. On April 5, 2011, TEPCO vice president Takashi Fujimoto announced that the company was canceling plans to build Reactors No. 7 and 8. 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.

Warnings and design critique

In 1990, the U.S.

Nuclear Regulatory Commission The Nuclear Regulatory Commission (NRC) is an independent agency of the United States government tasked with protecting public health and safety related to nuclear energy. Established by the Energy Reorganization Act of 1974, the NRC began opera ...

(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

(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. Filmmaker

Adam Curtis Adam Curtis (born 26 May 1955) is an English documentary filmmaker. Curtis began his career as a conventional documentary producer for the BBC throughout the 1980s and into the early 1990s. The release of '' Pandora's Box'' (1992) marked t ...

mentioned the risks of the type of

s cooling systems such as those in Fukushima I, and claimed the risks were known since 1971 in a series of documentaries in the BBC in 1992 and advised that PWR type reactors should have been used.

(TEPCO) operated the station and was warned their seawall was insufficient to withstand a powerful tsunami, but did not increase the seawall height in response. The Onagawa Nuclear Power Plant, operated by

, ran closer to the epicenter of the earthquake, but had much more robust seawalls of greater height and avoided severe accident.

Incidents and accidents

Prior to March 2011

1978

Fuel rods fell in reactor No. 3, causing a nuclear reaction. It took about seven and a half hours to place the rods back into proper positions. There was no record of the incident, as TEPCO had covered it up; interviews of two former workers in 2007 led to its discovery by TEPCO management.

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.

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.

November 2, 2010

Unit 5 had an automatic

SCRAM A scram or SCRAM is an emergency shutdown of a nuclear reactor effected by immediately terminating the fission reaction. It is also the name that is given to the manually operated kill switch that initiates the shutdown. In commercial reacto ...

while an operator was conducting an adjustment to the control blade insertion pattern. The

was caused by a reactor low water level alarm. The turbine tripped along with the reactor and there was no radiation injury to workers.

Nuclear disaster of March 11, 2011

On March 11, 2011, an earthquake categorized as 9.0 M_W on the

moment magnitude scale The moment magnitude scale (MMS; denoted explicitly with or Mw, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. It was defined in a 1979 pa ...

occurred at 14:46

Japan Standard Time , or , is the standard time zone in Japan, 9 hours ahead of UTC ( UTC+09:00). Japan does not observe daylight saving time, though its introduction has been debated on several occasions. During World War II, the time zone was often referred t ...

(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. The remaining reactors were shut down/

ed automatically after the earthquake, and the remaining decay heat of the fuel was being cooled with power from emergency generators. The subsequent destructive

tsunami A tsunami ( ; from ja, 津波, lit=harbour wave, ) is a series of waves in a water body caused by the displacement of a large volume of water, generally in an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater exp ...

with waves of up to that over-topped the station, which had seawalls, disabled emergency generators required to cool the reactors and

Spent fuel pool Spent fuel pools (SFP) are storage pools (or "ponds" in the United Kingdom) for spent fuel from nuclear reactors. They are typically 40 or more feet (12 m) deep, with the bottom 14 feet (4.3 m) equipped with storage racks designed to hold ...

s in Units 1–5. Over the following three weeks there was evidence of partial

nuclear meltdown A nuclear meltdown (core meltdown, core melt accident, meltdown or partial core melt) is a severe nuclear reactor accident that results in core damage from overheating. The term ''nuclear meltdown'' is not officially defined by the Internatio ...

s 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

s in Units 1, 3 and 4. Units 5 & 6 were reported on March 19, by the station-wide ''alert log updates'' of the

IAEA The International Atomic Energy Agency (IAEA) is an intergovernmental organization that seeks to promote the peaceful use of nuclear energy and to inhibit its use for any military purpose, including nuclear weapons. It was established in 195 ...

, 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". 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. Radiation releases from Units 1–4 forced the evacuation of 83,000 residents from towns around the plant. The triple meltdown also caused concerns about contamination of food and water supplies, including the 2011 rice harvest, and also the health effects of radiation on workers at the plant. Scientists estimate that the accident released 18 quadrillion becquerels of caesium-137 into the Pacific Ocean, contaminating 150 square miles of the ocean floor. The events at units 1, 2 and 3 have been rated at Level 5 each on the

International Nuclear Event Scale The International Nuclear and Radiological Event Scale (INES) was introduced in 1990 by the International Atomic Energy Agency (IAEA) in order to enable prompt communication of safety significant information in case of nuclear accidents. The ...

, 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).

After March 2011

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, contaminating the

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...

and

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

nearby. The leak was controlled and stored in a contained area. Contaminated water continues to accumulate at the plant, where it is filtered to remove most but not all radioactive particles.

July 9, 2013

TEPCO , also known as or TEPCO, is a Japanese electric utility holding company servicing Japan's Kantō region, Yamanashi Prefecture, and the eastern portion of Shizuoka Prefecture. This area includes Tokyo. Its headquarters are located in Uchi ...

officials reported that radioactive

caesium Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that a ...

was 90 times higher than it was 3 days prior (July 6), and that it may spread into the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...

. 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 Caesium-137 (), cesium-137 (US), or radiocaesium, is a radioactive isotope of caesium that is formed as one of the more common fission products by the nuclear fission of uranium-235 and other fissionable isotopes in nuclear reactors and nucle ...

was measured at 18 kilobecquerel per liter, 200 times the permitted level.

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.

April 12, 2016

Melted reactors were being cooled down with 300 tonnes of water each day.

September 10, 2019

Since the plant was destroyed by the earthquake and tsunami in 2011,

has continued to pump water onto the melted-down fuel cores to prevent them from once again overheating. This contaminated cooling water has collected on the site, where more than 1 million tons has been stored in hundreds of tall steel tanks. Large filtration systems are used to clean this water of most of its radioactive contaminants, but they cannot remove tritium, a radioactive isotope of hydrogen. As the tritium-contaminated water continues to accumulate, the plant operator says the site will run out of space to build more tanks by 2022, when it will have to dump the radioactive water directly into the

. It is not known yet how much water will be released by TEPCO, which will dilute the water first.

April 13, 2021

Japan's government approved the release of "treated" radioactive water from the plant into the Pacific Ocean – beginning in 2023 – over the course of an estimated 40 years.Yamaguchi, Mari,
Japan to start releasing Fukushima water into sea in 2 years
', The Associated Press, April 13, 2021

July 23, 2021

A note in the 2020 Tokyo Olympic games opening speech referenced the disaster and how Japan has recovered from the disaster.

Dismantling of reactors

The reactors will take 30–40 years to be decommissioned. On August 1, 2013, the Japanese Industry Minister

Toshimitsu Motegi is a Japanese politician and diplomat who currently serves as the Secretary-General of the Liberal Democratic Party. He has previously served as Minister for Foreign Affairs from 2019 to 2021, and as Minister of Economy, Trade and Industry f ...

approved the creation of a structure to develop the technologies and processes necessary to dismantle the four reactors damaged in the Fukushima accident. To reduce the flow of contaminated water into the Pacific Ocean, TEPCO spent ¥34.5 billion (approx. $324 million) to build a 1.5 kilometer-long underground wall of frozen soil around the plant, constructed by

Corporation. 1,500 , supercooled pipes were inserted into the ground in order to freeze the surrounding groundwater and soil. The wall ultimately failed to significantly decrease the groundwater flowing into the site. The cost of decommissioning and decontamination of the Fukushima Daiichi nuclear power plant has been estimated at $195 billion, which includes compensation payouts to victims of the disaster. The amount also includes decommissioning of Fukushima Daiichi reactors, which is estimated at $71 billion. TEPCO will shoulder $143 billion of decommissioning and decontamination, while the Ministry of Finance of Japan will provide $17 billion. Other power companies will also contribute to the cost. On September 26, 2020, Prime Minister

Yoshihide Suga is a Japanese politician who served as Prime Minister of Japan and President of the Liberal Democratic Party (LDP) from 2020 to 2021. He had served as Chief Cabinet Secretary during the second administration of Prime Minister Shinzo Abe fro ...

visited the Daiichi Nuclear Power Plant to show that his cabinet prioritized the reconstruction of areas that were affected by natural and nuclear disasters.

References

External links

Fukushima Daiichi Decommissioning Official site

Archived photo
Units 1–4 can be seen from left to right.
3D Google Earth view
{{Authority control Former nuclear power stations in Japan 1967 establishments in Japan Fukushima Daiichi nuclear disaster Buildings and structures in Fukushima Prefecture Tokyo Electric Power Company Nuclear power stations with closed reactors Ōkuma, Fukushima