The is a
nuclear power plant
A nuclear power plant (NPP), also known as a nuclear power station (NPS), nuclear generating station (NGS) or atomic power station (APS) is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power st ...
located on a site in the town of
Naraha and
Tomioka in the
Futaba District of
Fukushima Prefecture
is a Prefectures of Japan, prefecture of Japan located in the Tōhoku region of Honshu. Fukushima Prefecture has a population of 1,771,100 () and has a geographic area of . Fukushima Prefecture borders Miyagi Prefecture and Yamagata Prefecture ...
, Japan. The
Tokyo Electric Power Company
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 Uchisaiwaicho, Chiyoda, Tokyo, an ...
(TEPCO) runs the plant.
After the
2011 Tōhoku earthquake and tsunami
On 11 March 2011, at 14:46:24 Japan Standard Time, JST (05:46:24 UTC), a 9.0–9.1 Submarine earthquake, undersea megathrust earthquake occurred in the Pacific Ocean, east of the Oshika Peninsula of the Tōhoku region. It lasted approx ...
, the four reactors at Fukushima Daini
automatically shut down.
While the sister plant
Fukushima Daiichi Nuclear Power Plant
The is a disabled nuclear power plant located on a site in the towns of Ōkuma, Fukushima, Ōkuma and Futaba, Fukushima, Futaba in Fukushima Prefecture, Japan. The plant Fukushima Daiichi nuclear disaster, suffered major damage from the 201 ...
, approximately to the north, suffered extensive damage, the Daini Plant was back under control within two days, reaching cold shutdown.
The plant has not been operating since, and in July 2019 a decision to decommission the plant was made.
Description
All reactors in the Fukushima II Nuclear Power Plant are
BWR-5 type with electric power of 1,100 MW each (net output: 1,067 MW each).
The reactors for units 1 and 3 were supplied by
Toshiba
is a Japanese multinational electronics company headquartered in Minato, Tokyo. Its diversified products and services include power, industrial and social infrastructure systems, elevators and escalators, electronic components, semiconductors ...
, and for units 2 and 4 by
Hitachi
() is a Japanese Multinational corporation, multinational Conglomerate (company), conglomerate founded in 1910 and headquartered in Chiyoda, Tokyo. The company is active in various industries, including digital systems, power and renewable ener ...
. Units 1–3 were built by
Kajima while the unit 4 was built by
Shimizu and
Takenaka.
Electrical connections
The Fukushima Daini plant is connected to the rest of the power grid by the Tomioka Line () to the Shin-Fukushima (New Fukushima)
substation.
Events
1989 incident
In January 1989, an impeller blade on one of the reactor coolant pumps in Unit 3 broke at a weld, causing a large amount of metal debris to flow throughout the primary loop. As a result, the reactor was shut down for a considerable length of time.
2011 earthquake and tsunami
The March 11,
2011 Tōhoku earthquake resulted in maximum horizontal ground accelerations of 0.21 g (2.10 m/s
2) to 0.28 (2.77 m/s
2) at the plant site, which is well below the design basis.
The
design basis accident for an earthquake was between 0.42
g (4.15 m/s
2) and 0.52 g (5.12 m/s
2) and for a tsunami was 5.2 m.
All four units were automatically shut down (
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 reactor ...
) immediately after the earthquake,
[ and the diesel engines were started to power the reactor cooling.]
A worker died of injuries from the earthquake when he was trapped in the crane operating console of the exhaust stack.[:"We sincerely pray for the repose of his soul."]
The tsunami
A tsunami ( ; from , ) 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 underwater explosions (including detonations, ...
that followed the earthquake and inundated the plant was initially estimated by TEPCO to be 14 meters high, which would have been more than twice the designed height.[
Other sources give the tsunami height at Fukushima Daini plant at 9-meter-high, while the Fukushima Daiichi plant was hit by a 13-meter-high tsunami.
The tsunami caused the plant's seawater pumps, used to cool reactors, to fail.
Of the plant's four reactors, three were in danger of meltdown.
One external high-voltage power line still functioned, allowing plant staff in the central control room to monitor data on internal reactor temperatures and water levels.
2,000 employees of the plant worked to stabilize the reactors.
Some employees connected over 9 kilometers of cabling using 200-meter sections of cable, each weighing more than a ton, from their Rad Waste Building to other locations onsite.
The steam-powered reactor core isolation cooling system (RCIC) in all 4 units was activated and ran as needed to maintain water level.
At the same time, operators utilized the safety relief valve systems to keep the reactor pressures from getting too high by dumping the heat to the suppression pools.][
In unit 3, one seawater pump remained operational and the residual heat removal system (RHR) was started to cool the suppression pool and later brought the reactor to cold shutdown on March 12.
In units 1, 2, and 4 heat removal was unavailable, so the suppression pools began heating up and on March 12, the water temperature in the pools of units 1, 2, and 4 reached 100 °C between 05:30 and 06:10 JST,][reports fo]
reactor 1
an
of Tokyo Electric, received 11:50 JST removing the ability to remove pressure from the reactor and drywell.[
Operators had to also prepare an alternate injection line for each unit, as the RCIC can run indefinitely only while there is sufficient pressure and steam in the reactor to drive its turbine.
Once the reactor pressure drops below a certain level, the RCIC shuts down automatically.
The normal electrically driven ]Emergency Core Cooling System
The three primary objectives of nuclear reactor safety systems as defined by the U.S. Nuclear Regulatory Commission are to shut down the reactor, maintain it in a shutdown condition and prevent the release of radioactive material.
Reactor protec ...
s (ECCS) were for the most part unavailable due to the loss of the ultimate heat sink and damage to some of the electrical infrastructure.
Operators prepared for this and set up an alternate injection line using a non-emergency system known as the ''Makeup Water Condensate'' (MUWC) system to maintain water level which was an accident mitigation method TEPCO put in place at all its nuclear plants.
The system was started and stopped in all 4 units, including unit 3, as needed to maintain the water level.
The RCICs in each unit later shut down due to low reactor pressure.
The MUWC and the ''makeup water purification and filtering'' (MUPF) systems were also used to try to cool the suppression pool and drywell in addition to the reactor to prevent the drywell pressure from getting too high.
Operators were later able to restore the High Pressure Core Spray portion of the ECCS in unit 4 and switched emergency water injection for unit 4 from the MUWC system to the HPCS.
While the water level was maintained in the three cores using emergency water injection, pressures in the containment vessel continued to rise due to lack of suppression pool cooling and the operators prepared to vent the containments making restoration of heat removal urgent.
Unit 1 was prioritized as it had the highest drywell pressure.
Cold shutdown
The ultimate heat sink was restored on March 13 when the service seawater system pumps in the pump room were repaired in units 1, 2 and 4.
This allowed the restoration of the normal ECCS and heat removal systems to operable status and cooling was switched to the ''Residual Heat Removal System'' (RHR) portion of the ECCS.
The RHR systems were first activated to cool down the suppression pools (torus) and drywells to operable status, and water injections were made to the reactors using the ''Low Pressure Coolant Injection'' (LPCI) mode as needed.
When the suppression pool was cooled down to below 100 °C, the RHR was switched to the shutdown cooling mode and brought the reactors to a cold shutdown.[
Coolant temperatures below 100 °C ( cold shutdown) were reached in reactor 2 about 34 hours after the emergency shut down (]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 reactor ...
).
Reactors 1 and 3 followed at 1:24 and 3:52 on March 14 and Reactor 4 at 7:00 on March 15.
By March 15, all four reactors of Fukushima II reached cold shutdown, which remained non-threatening.
The loss of cooling water at reactors 1, 2 and 4 was classified a level 3 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 s ...
(serious incident) by Japanese authorities as of March 18.
Officials made preparations for release of pressure from the plant on March 12,
but no pressure release was necessary.[
An evacuation order was issued to the people living within of the plant,] subsequently expanded to .[ Smoke from Fukushima Daini nuclear plant]
Air traffic was restricted in a radius around the plant, according to a NOTAM
A NOTAM (ICAO & FAA: Notice to Airmen, CAA: Notice to Aviation or, for the FAA from 2021 to 2025, Notice to Air Missions) is a notice filed with an aviation authority to alert aircraft pilots of potential hazards along a flight route or at a loca ...
.
These zones were later superseded by the 20 km evacuation and 30 km no-fly zones around Fukushima Daiichi on March 12 and 15, respectively.
, 7,000 tons of seawater from the tsunami remained in the plant.
The plant planned to release it all back into the ocean, as the tanks and structures holding the water were beginning to corrode.
Approximately 3,000 tons of the water was found to contain radioactive substances, and Japan's Fisheries Agency refused permission to release that water back into the ocean.
Restoration
On December 26, 2011, the Prime Minister officially cancelled the nuclear emergency declaration for the Fukushima Daini plant officially ending the incident.
On February 8, 2012, the plant was opened to news media for the first time since the 2011 Tōhoku earthquake and tsunami.
The evacuation order was partly rescinded for Daini evacuees in August 2012. Some of the residents, such as the 7200 at Naraha, were permitted to return during daylight hours only, but others were ordered to remain away. The area did not become seriously contaminated and was safe to visit without protective clothing. In 2015, the evacuation order for Naraha was completely lifted, allowing residents to return and reconstruction efforts to begin. Naraha is the first of a number of towns in the area to have had its evacuation order removed.
2016 earthquake
On Tuesday, November 22, 2016, a magnitude 6.9 earthquake struck Japan
Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
east southeast of Namie
is a Towns of Japan, town located in Fukushima Prefecture, Japan. the town has a population of 1,238 in 794 households, although the official registered population was 17,114 in 6853 households. The total area of the town is .
The town was ev ...
, Fukushima Prefecture
is a Prefectures of Japan, prefecture of Japan located in the Tōhoku region of Honshu. Fukushima Prefecture has a population of 1,771,100 () and has a geographic area of . Fukushima Prefecture borders Miyagi Prefecture and Yamagata Prefecture ...
at a depth of . The shock had a maximum intensity of VII ''(Very strong)''. 14 people were injured and more than 1,900 homes briefly lost electricity. Though a warning of a possible tsunami of in height was issued, a wave was reported by NHK
, also known by its Romanization of Japanese, romanized initialism NHK, is a Japanese public broadcasting, public broadcaster. It is a statutory corporation funded by viewers' payments of a television licence, television license fee.
NHK ope ...
in the port of Onahama of Iwaki, Fukushima
is a Cities of Japan, city located in Fukushima Prefecture, Japan. , Iwaki had a population of 322,019 in 143,500 households, and population density of 261 persons per km². The total area of the city is , making it the largest city in the prefec ...
; a wave hit Sōma, Fukushima
is a Cities of Japan, city located in Fukushima Prefecture, Japan. , the city had an estimated population of 34,631, and a population density of 180 persons per km2 in 14,358 households. The total area of the city is .
Geography
Sōma is locate ...
; and another wave in height struck the Fukushima Daiichi Nuclear Power Plant
The is a disabled nuclear power plant located on a site in the towns of Ōkuma, Fukushima, Ōkuma and Futaba, Fukushima, Futaba in Fukushima Prefecture, Japan. The plant Fukushima Daiichi nuclear disaster, suffered major damage from the 201 ...
site after the 6.9 shock. Chief Cabinet Secretary Yoshihide Suga said that the third reactor's 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 ...
cooling systems at Fukushima Daini had stopped as a result of the earthquake; TEPCO later reported the restart of the spent fuel cooling system after only 100 minutes of stoppage.
Decommissioning
On 31 July 2019, the TEPCO board of directors decided to decommission the plant, in response to local demands for a decision. Decommissioning is expected to take more than 40 years to complete, and will include moving spent nuclear fuel
Spent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor (usually at a nuclear power plant). It is no longer useful in sustaining a nuclear reaction in an ordinary thermal reactor and ...
from 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 to on-site dry cask storage
Dry cask storage is a method of storing high-level radioactive waste, such as spent nuclear fuel that has already been cooled in a spent fuel pool for at least one year and often as much as ten years. Casks are typically steel cylinders that are ...
.[
]
See also
* Nuclear power in Japan
Nuclear power generated 5.55% of Japan's electricity in 2023.
The country's nuclear power industry was heavily influenced by the Fukushima accident, caused by the 2011 Tōhoku earthquake and tsunami. Before 2011, Japan was generating up to 30% of ...
* Fukushima Daiichi nuclear disaster
The Fukushima nuclear accident was a major nuclear accident at the Fukushima Daiichi Nuclear Power Plant in Ōkuma, Fukushima, Japan, which began on 11 March 2011. The cause of the accident was the 2011 Tōhoku earthquake and tsunami, which r ...
* List of boiling water reactors
* List of nuclear power plants in Japan
* Lists of nuclear disasters and radioactive incidents
These are lists of nuclear disasters and radioactive incidents.
Main lists
* List of nuclear and radiation accidents and incidents
* List of nuclear and radiation accidents by death toll
* List of civilian nuclear accidents
* List o ...
* List of civilian nuclear accidents
References
External links
Tokyo Electric Power Company 東京電力
**
*
* ttp://allthingsnuclear.org/ All Things Nuclearbr>H2O-project: Extensive information about the events during and after the tsunami
{{DEFAULTSORT:Fukushima Ii Nuclear Power Plant
Former nuclear power stations in Japan
1970s establishments in Japan
Fukushima nuclear accident
Power stations in Fukushima Prefecture
Tokyo Electric Power Company