The story around fukusima 1 and 2 nuclear plants

Posted: 28/03/2011 in World


The Fukushima I Nuclear Power Plant ( Fukushima Dai-ichi Genshiryoku Hatsudensho?, Fukushima I NPP), also known as Fukushima Dai-ichi (dai-ichi means «number one»), is a nuclear power plant located on a 3,500,000-square-metre (860-acre) site[1] in the towns of Okuma and Futaba in the Futaba District of Fukushima Prefecture, Japan.

First commissioned in 1971, the plant consists of six boiling water reactors (BWR). These light water reactors[2] drove electrical generators with a combined power of 4.7 GWe, making Fukushima I one of the 15 largest nuclear power stations in the world. Fukushima I was the first nuclear plant to be constructed and run entirely by the Tokyo Electric Power Company (TEPCO). The plant suffered major damage from the 9.0 earthquake and subsequent tsunami that hit Japan on March 11, 2011, disabling the reactor cooling systems and triggering a widespread evacuation surrounding the plant, and is not expected to reopen.

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.[3] Architectural design for General Electric’s units was done by Ebasco. All construction was done by Kajima.[4] Since September 2010, Unit 3 has been fueled by a small fraction (6%)[5] of mixed-oxide (MOX) fuel, rather than the low enriched uranium (LEU) used in the other reactors.[6][7] Units 1–5 were built with Mark I type (light bulb torus) containment structures, Unit 6 has a Mark II type (over/under) containment structure.[8][9][10]
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.[11] In February 2011, Japanese regulators granted an extension of ten years for the continued operation of the reactor.[12] It was damaged during the 2011 Tōhoku earthquake and tsunami.[13]
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.[8] 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.[14] 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.[8] The design basis for tsunamis was 5.7 meters.[15]





Reactor data
Unit Fukushima I – 1
Type[16] BWR-3
Start construction[17] July 25, 1967
First criticality[17] October 10, 1970
Commercial operation[17] March 26, 1971
Electric power[17] 460 MW
Reactor supplier[16] General Electric
Architecture[4] Ebasco
Construction[4] Kajima
Fuel LEU

Unit Fukushima I – 2
Type[16] BWR-4
Start construction[17] June 9, 1969
First criticality[17] May 10, 1973
Commercial operation[17] July 18, 1974
Electric power[17] 784 MW
Reactor supplier[16] General Electric
Architecture[4] Ebasco
Construction[4] Kajima
Fuel LEU

Unit Fukushima I – 3
Type[16] BWR-4
Start construction[17] December 28, 1970
First criticality[17] September 6, 1974
Commercial operation[17] March 27, 1976
Electric power[17] 784 MW
Reactor supplier[16] Toshiba
Architecture[4] Toshiba
Construction[4] Kajima
Fuel LEU/MOX[6]

Unit Fukushima I – 3
Type[16] BWR-4
Start construction[17] December 28, 1970
First criticality[17] September 6, 1974
Commercial operation[17] March 27, 1976
Electric power[17] 784 MW
Reactor supplier[16] Toshiba
Architecture[4] Toshiba
Construction[4] Kajima
Fuel LEU/MOX[6}

Unit Fukushima I – 4
Type[16] BWR-4
Start construction[17] February 12, 1973
First criticality[17] January 28, 1978
Commercial operation[17] October 12, 1978
Electric power[17] 784 MW
Reactor supplier[16] Hitachi
Architecture[4] Hitachi
Construction[4] Kajima
Fuel LEU/MOX[6}


Unit Fukushima I – 5
Type[16] BWR-4
Start construction[17] May 22, 1972
First criticality[17] August 26, 1977
Commercial operation[17] April 18, 1978
Electric power[17] 784 MW
Reactor supplier[16] Toshiba
Architecture[4] Toshiba
Construction[4] Kajima
Fuel LEU/MOX[6}


Unit Fukushima I – 6
Type[16] BWR-5
Start construction[17] October 26, 1973
First criticality[17] March 9, 1979
Commercial operation[17] October 24, 1979
Electric power[17] 1,100 MW
Reactor supplier[16] General Electric
Architecture[4] Ebasco
Construction[4] Kajima
Fuel LEU/MOX[6}


Fukushima I – 7 (planned)[18]
ABWR
April 2012
October 2016
1,380 MW


Fukushima I – 8 (planned)[18]
ABWR
April 2012
October 2017
1,380 MW

Operating history
The plant reactors came online from 1970 through 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.[19][20] On Feb 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.[21]

Incidents

On February 25, 2009 a manual shutdown was initiated during the middle of a startup 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 4:03am due to a pressure increase to 1,029.8 psi, exceeding the regulatory limit of 1,002.2 psi. 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 4:25am. Later, at 8:49am 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 25 regular inspection which begun on October 18, 2008.[22]
On 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 2:23pm a control blade drift alarm went off. On later inspection it was found that several of the rods had been unintentionally inserted.[23]
On 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.[24]

Nuclear accidents of 2011
Main article: Fukushima I nuclear accidents

Before and after images of the Unit 1 from March 12, 2011, which suffered a hydrogen explosion.
On March 11, 2011 an earthquake categorised as 9.0 MW on the moment magnitude scale occurred at 14:46 Japan Standard Time (JST) off the northeast coast of Japan. Reactors 4, 5 and 6 had been shut down prior to the earthquake for planned maintenance.[25][26] The remaining reactors were shut down automatically after the earthquake, but the subsequent tsunami flooded the plant, knocking out emergency generators needed to run pumps which cool and control the reactors. The flooding and earthquake damage prevented assistance being brought from elsewhere. Over the following days there was evidence of partial nuclear meltdowns in reactors 1, 2 and 3; hydrogen explosions destroyed the upper cladding of the building housing reactors 1 and 3; an explosion damaged reactor 2’s containment; and severe fires broke out at reactor 4.
The Japanese authorities rated the events at reactors 1, 2 and 3 as a level 5 (Accident With Wider Consequences) on the International Nuclear Event Scale, while the events at reactor 4 were placed at level 3 (Serious incident).



The Fukushima II Nuclear Power Plant, or Fukushima Dai-ni, is located 11.5 kilometres (7.1 mi) to the south and also run by TEPCO.
The Fukushima II Nuclear Power Plant (Fukushima Dai-Ni ( pronunciation) Genshiryoku Hatsudensho?, Fukushima II NPP, 2F), or Fukushima Dai-ni (dai-ni means «number two»), is a nuclear power plant located on a 1,500,000-square-metre (370-acre) site[1] in the town of Naraha and Tomioka in the Futaba District of Fukushima Prefecture, Japan. The Tokyo Electric Power Company (TEPCO) runs the plant.
After the 2011 Tōhoku earthquake and tsunami, the four reactors at Fukushima II automatically shut down without incident.[2]
Japan’s worst nuclear accident occurred at TEPCO’s Fukushima I Nuclear Power Plant, or Fukushima Dai-ichi, 11.5 kilometres (7.1 mi) to the north, after the same March 11 earthquake.

All reactors in the Fukushima II Nuclear Power Plant are BWR-5 type[3] with electric power of 1,100 MW each (net output: 1,067 MW each).[4]
The reactors for units 1 and 3 were supplied by Toshiba, and for units 2 and 4 by Hitachi. Units 1–3 were built by Kajima while the unit 4 was built by Shimizu and Takenaka.[4] The design basis for an earthquake was between 0.42 g (4.15 m/s2) and 0.52 g (5.12 m/s2) and for a tsunami was 5.2 m.[5]
Unit First criticality Installation costs (yen/MW) Reactor supplier Architecture Construction
1 31/07/1981 250,000,000 Toshiba Toshiba Kajima
2 23/06/1983 230,000,000 Hitachi Hitachi Kajima
3 14/12/1984 290,000,000 Toshiba Toshiba Kajima
4 17/12/1986 250,000,000[6] Hitachi Hitachi Shimizu
Takenaka
[edit]Events

[edit]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 considerably long time, making this one of the most serious incidents at the site.[citation needed]

2011 earthquake and tsunami

The March 11, 2011 Tōhoku earthquake resulted in ground accelerations of 0.19 g (1.86 m/s2) to 0.28 (2.77 m/s2) at the plant site, which is well below the design basis. [5] All four units were automatically shut down immediately after the earthquake, according to Nuclear Engineering International,[2] and the diesel engines were started to power the reactor cooling.[7] TEPCO estimated that the tsunami that followed the earthquake and inundated the plant was 14 meters high which is more than twice the designed height.[5] This flooded the pump rooms used for heat transfer to the sea, the ultimate heat sink of the reactors.[7] While the cooling system for unit 3 was undamaged, the other reactors were affected. The cooling systems remained operational, but heated up due to the lack of a heat sink. The high pressure coolant injection (HPCI) system (powered by reactor steam) was used as additional cooling.[7] On March 12, the cooling system for three reactors (numbers 1, 2 and 4) at the torus had topped 100 °C between 05:30 and 06:10 JST,[8][9][10] rendering all cooling systems (depending on temperature difference between the torus and the reactor) ineffective.[7] The coolant systems in the pump room were repaired and activated in Units 1, 2 and 4 in the days following the emergency shutdown after cooling could recommence[8] Coolant temperatures below 100 °C (cold shutdown) were reached in reactor 2 about 34 hours after the emergency shut down (SCRAM).[8] Reactors 1 and 3 followed at 1:24 and 3:52 on March 14 and Reactor 4 at 7:00 on March 15.[11] The loss of cooling water at reactors 1, 2 and 4 was classified a level 3 on the International Nuclear Event Scale (serious incident) by Japanese authorities as of March 18.[12][13][14]
Officials made preparations for release of pressure from the plant on March 12.[15][16] As of March 20, however, no pressure release had been reported.[8][17]
An evacuation order was issued to people living within 3 kilometres (1.9 mi) of the plant,[18] subsequently expanded to 10 km (6.2 mi).[19] Air traffic was restricted in a 10 km (6.2 mi) radius around the plant, according to a NOTAM.[20] These zone were superseded by the 20 km evacuation and 30 km no-fly zones around Fukushima I on March 12 and 15, respectively.
TEPCO announced that a worker who had been seriously injured by the earthquake, and trapped in the crane operating console of the exhaust stack was transported to the ground at 5:13 p.m. and confirmed dead at 5:17 p.m.

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