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Chronological outline of the nuclear accidents in Japan

Mr. Kohta Juraku, the liaison from Univeristy of Tokyo made a chronological summary of the Nuclear accident in Japan. Download it here.

Date Time (JST) Place/Site/Plant Description of Event
7/21/2010 10:00 Fukushima-Daiichi (1) #1 Reactor is started
(after regular maintenance: 72 / 400 fuel bundles were replaced)
8/14/2010 5:24 Fukushima-Daiichi (1) #6 Reactor is stopped for regular maintenance (184 / 764 fuel bundles are planned to be replaced)
8/22/2010 5:14 Fukushima-Daiichi (1) #1 Reactor is stopped to have additional maintenance
9/22/2010 6:08 Fukushima-Daiichi (1) #3 Reactor is started
(after regular maintenance: 148 / 548 fuel bundles were replaced, 32 new bundles are MOX fuel)
9/24/2010 10:02 Fukushima-Daiichi (1) #1 Reactor is started again
9/30/2010 13:30 Fukushima-Daiichi (1) #3 Rated operation is started (constant thermal output)
11/17/2011 17:39 Fukushima-Daiichi (1) #2 Reactor is started (after regular maintenance: 116 / 548 fuel bundles were replaced)
11/29/2010 18:00 Fukushima-Daiichi (1) #4 Reactor is stopped for regular maintenance
12/6/2011 17:24 Fukushima-Daiichi (1) #2 Rated operation is started (constant thermal output)
1/3/2011 4:13 Fukushima-Daiichi (1) #5 Reactor is stopped for regular maintenance (124 / 548 fuel bundles are planned to be replaced)
3/11/2011 14:00 Onagawa #2 Start up the plant

14:46
Earthquake Details (source:USGS)

This event has been reviewed by a seismologist.
Magnitude: 9.0
Date-Time:
Friday, March 11, 2011 at 05:46:23 UTC
Friday, March 11, 2011 at 02:46:23 PM at epicenter
Location: 38.322°N, 142.369°E
Depth: 32 km (19.9 miles) set by location program
Region: NEAR THE EAST COAST OF HONSHU, JAPAN
Distances:
129 km (80 miles) E of Sendai, Honshu, Japan
177 km (109 miles) E of Yamagata, Honshu, Japan
177 km (109 miles) ENE of Fukushima, Honshu, Japan
373 km (231 miles) NE of TOKYO, Japan


Onagawa #1-3 Automatic stop due to the earthquake


Fukushima-Daiichi (1) #1-3 Automatic stop due to the earthquake

15:30 Onagawa #1 Small fire occur at the B1 floor of the turbine building
Extinguished by fire crew
(Reason: spark from high-voltage line)


Fukushima-Daiichi (1) #1-3 All (13) diesel generators at Fukushima-1 site (including generators in #4-6) are broken
"Station Black Out" in all plants at Fukushima-1 site

16:15
NISA receives the notice of "specific incident"at Fukushima-1 #1-3 from TEPCO up to this point

16:36
NISA receives the notice of "nuclear emergency"at Fukushima-1 #1&2 from TEPCO up to this point

19:03
Prime Minister Mr. Kan declares "nuclear emergency" for Fukushima-1 plants


Fukushima-Daiichi (1) #2 Water level of reactor is decreased

20:30 Fukushiba-Daiichi (1) #1 & 2 ECCS is completely stopped
Isolation Cooling System is also stopped

21:23 Fukushima-Daiichi (1) Evacuation order for residents in 3km in radius from the Fukushima-1 site
Order of indoor waiting for residents in 3-10km from the Fukushima-1 site


Fukushima-Daini (2) #1 Pressure in containment vessel is increased
ECCS is activated

22:00 Fukushima-Daiichi (1) #2 Water level inside pressure vessel: 340cm above the top of fuel rod
(530cm above under the normal condition)

22:00 Fukushima-Daini (2) TEPCO annouces that all 4 reactors are following statuses:
Reactors are stopped and the levels of water are stable
External power is secured at all plants
All main steam isolation valves are closed
No leak of coolant inside containment vessels

22:30 Fukushima-Daiichi (1) #1-3 Power source cars are sent to the site
Levels of the water are maintained (?)
The Residual Heat Removal System is not functioned


Fukushima-Daiichi (1) #1 Pressure in pressure vessel get 1.5 times as design value



A poer cource car are arrived at the site
Part of power supply for #2 plant is secured
3/12/2011 0:00 Fukushima-Daiichi (1) 3 or 4 power source cars are on guard at the site
Part of required cables are secured, the rest is being procured
Batteries are being on passage from Hirono thermal power plant


Fukushima-Daiichi (1) #1 Pressure in pressure vessel get 2.1 times as design value (840kPa)


Fukushima-Daini (2) #1,2 & 4 Temperatures in suppression pools are over 100 degree Celsius
Cooling capacity of the plants are lost

3:00 Fukushima-Daini (2) TEPCO announces that the Isolation Coolant Systems are stopped and water is injected by the Makeup Water Condansate Systems at #3-4 plants

3:00 Fukushima-Daini (2) #1 The Isolation Coolant Systems are stopped and water is injected by the Makeup Water Condansate Systems

4:50 Fukushima-Daini (2) #1 The Isolation Coolant Systems are stopped and water is injected by the Makeup Water Condansate Systems

4:40 Fukushima-Daiichi (1) Significant increase of radiation dose at the site is detected
866 nGy/h of gamma ray at the main gate of the site

4:50 Fukushima-Daini (2) #2 The Isolation Coolant Systems are stopped and water is injected by the Makeup Water Condansate Systems

4:50 Fukushima-Daiichi (1) 1002 nGy/h of gamma ray at the main gate of the site

5:10 Fukushima-Daiichi (1) 1307 nGy/h of gamma ray at the main gate of the site

5:10 Fukushima-Daiichi (1) 1590 nGy/h of gamma ray at the main gate of the site

5:22 Fukushima-Daini (2) #1 Temperatures in the suppression chamber surpasses 100 degree Celcius
The suppression chamber loses their capacity to suppress pressure
TEPCO sends the notice of "nuclear emergency"at Fukushima-2 #1 to NISA

5:32 Fukushima-Daini (2) #2 Temperatures in the suppression chamber surpasses 100 degree Celcius
The suppression chamber loses their capacity to suppress pressure
TEPCO sends the notice of "nuclear emergency"at Fukushima-2 #2 to NISA

5:44 Fukushima-Daiichi (1) Evacuation order for residents in 10km in radius from the Fukushima-1 site by the national government

6:00 Fukushima-Daiichi (1) NISA annouces significant increase of radiation dose at the Fukushima-1 site
150 ?Sv/h at the Central Control Room of #1 plant (1000 times higher than usual)
About 8 times higher radiation dose than usual at the main gate of the #1 site is also explained

6:00 Fukushima-Daiichi (1) TEPCO annouces that they are preparing to make a procedure for release pressure from containment vessel at the plants which is not confirmed water coolant circulation (such as by Isolation Coolant System)

6:07 Fukushima-Daini (2) #4 Temperatures in the suppression chamber surpasses 100 degree Celcius
The suppression chamber loses their capacity to suppress pressure
TEPCO sends the notice of "nuclear emergency"at Fukushima-2 #4 to NISA

6:07 Fukushima-Daiichi (1) Evacuation in 3km radius from the site is completed

6:40 Fukushima-Daiichi (1) 4.92?Sv/h at the main gate of the site


Fukushima-Daiichi (1) #1 &  2 Governmental order to suppress the pressure of containment vessels

7:30 Fukushima-Daiichi (1) Radiation doses of 2 monitoring point around the main gate of the site are increased: 5.1?Sv/h (MP6: main gate) & 2.5?Sv/h (MP8: observatory)

7:45 Fukushima-Daini (2) Prime Minister Mr. Kan declare "nuclear emergency" for Fukushima-2 plants


Fukushima-Daini (2) Evacuation order for residents in 3km in radius from the Fukushima-2 site
Order of indoor waiting for residents in 3-10km from the Fukushima-2 site

7:50 Fukushima-Daiichi (1) & -Daini (2) 51 power source cars are arrived at sites

8:19 Fukushima-Daini (2) #1 Alart: the position of a control rod is N/A

9:00 Fukushima-Daiichi (1) #1 Procedure for pressure release from the containment vessel is started at the #1 plant

9:43 Fukushima-Daini (2) #1 Preparation for the pressure release from the containment vessel is started

10:20 Fukushima-Daiichi (1) 180.2?Sv/h at the main gate of the site

10:30 Fukushima-Daiichi (1) 385.5?Sv/h at the main gate of the site

10:33 Fukushima-Daini (2) #2 Preparation for the pressure release from the containment vessel is started

10:40 Fukushima-Daiichi (1) 162.9?Sv/h at the main gate of the site

10:43 Fukushima-Daini (2) #1 Alart on the position of a control rod is turned off spontaneously

10:50 Fukushima-Daiichi (1) 7.04?Sv/h at the main gate of the site

10:58 Fukushima-Daini (2) #2 Preparation for the pressure release from the containment vessel is completed

11:44 Fukushima-Daini (2) #4 Preparation for the pressure release from the containment vessel is started

11:52 Fukushima-Daini (2) #4 Preparation for the pressure release from the containment vessel is completed


Fukushima-Daiichi (1) #1 Cs-137 is detected at the 2 monitoring posts around the site
NISA announces the possibility of coremelt in the #1 reactor


Fukushima-Daiichi (1) #1 Water level inside pressure vessel: 150cm under the top of fuel rod
Water pumping by fire engine is announced



21,000 metric litter of water has been pumped in
Pressure inside containment vessel: 7.54 atm

12:08 Fukushima-Daini (2) #3 Preparation for the pressure release from the containment vessel is started

12:13 Fukushima-Daini (2) #3 Preparation for the pressure release from the containment vessel is completed

12:15 Fukushima-Daini (2) #3 Reactor is completely stopped

14:30 Fukushima-Daiichi (1) #1 Vent of containment vessel is opened

15:00 Fukushima-Daini (2) #4 TEPCO announces that the water injection system is switched from the Makeup Water Condansate Systems to the HPCS (High Pressure Core Spray System)

15:29 Fukushima-Daiichi (1) 1015?Sv/h at the border of the site

15:36 Fukushima-Daiichi (1) #1 Hydrogen explosion is occurred
The top 1/3 of the reactor building is blowen off
4 workers are injured


Fukushima-Daini (2) Evacuation order for residents in 10km in radius from the Fukushima-2 site by the national government

18:00 Fukushima-Daini (2) #1 TEPCO announces that they are making recovery efforts to secure power supply for the pressure release procedure

18:25 Fukushima-Daini (1) Evacuation order for residents in 20km in radius from the Fukushima-1 site by the national government

18:30 Fukushima-Daini (2) #1 Preparation for the pressure release from the containment vessel is completed

20:05 Fukushima-Daiichi (1) #1 Governmental order to pump in sea water

20:20 Fukushima-Daiichi (1) #1 Sea water pumping to pressure vessel is begun

22:15 Fukushima-Daiichi (1) #1 Sea water pumping is suspended due to an big after quake
3/13/2011
Fukushima-Daiichi (1) #1 Sea water pumping is resumed

2:44 Fukushima-Daiichi (1) #3 HPCI (high pressure coolant injection) is stopped due to battery exhaution

4:15 Fukushima-Daiichi (1) #3 Rapid decrease of water level inside the pressure vessel
Some of top part of fuel rods are no longer covered by water

5:10 Fukushima-Daiichi (1) #3 Procedure to switch to all of other coolant systems are failed
TEPCO sends the notice of "nuclear emergency"at Fukushima-1 #3 to NISA

8:20 Fukushima-Daiichi (1) 882?Sv/h at the border of the site
TEPCO sends the notice of "nuclear emergency"at Fukushima-1 to NISA

8:33 Fukushima-Daiichi (1) 1204.2?Sv/h at the border of the site

8:41 Fukushima-Daiichi (1) #3 Vent of containment vessel is opened

9:08 Fukushima-Daiichi (1) #3 Sweet water pumping is started

9:20 Fukushima-Daiichi (1) #3 Boric acid solution is injected
Discharge of gus from the containment vessel is started

9:30 Fukushima-Daiichi (1) 70.3?Sv/h at the border of the site (MP1)


Fukushima-Daiichi (1) #1 NISA annouces that the core of #1 reactore seems to be filled by injected sea water

12:00 Fukushima-Daiichi (1) #3 Decrease of water level inside the pressure vessel is observed

12:43 Fukushima-Daini (2) #1 Alart: the position of a control rod is N/A (other signals show the rod is properly inserted)

12:55 Fukushima-Daiichi (1) #3 Water level inside pressure vessel: 190cm under the top of fuel rod

13:12 Fukushima-Daiichi (1) #3 Sea water pumping is started

14:00 Fukushima-Daiichi (1) #2 #2 plant maintains its coolant system

14:20 Fukushima-Daiichi (1) #3 Water level inside pressure vessel: 220cm under the top of fuel rod

15:00 Fukushima-Daiichi (1) #3 Water level inside pressure vessel: 200cm under the top of fuel rod
3/14/2011 1:10 Fukushima-Daiichi (1) #1 & 3 Water pumping is suspended due to the lack of sea water

1:24 Fukushima-Daini (2) #1 The Residual Heat Removal System (B) is recovered
Cooling down of suppression pool is started

3:20 Fukushima-Daiichi (1) # 3 Water pumping is resumed

6:50 Fukushima-Daiichi (1) #3 High pressure value inside containment vessel: 530kPa

6:50 Fukushima-Daiichi (1) #2 Pressure inside containment vessel is begun to increase

7:13 Fukushima-Daini (2) #2 The Residual Heat Removal System is recovered
Cooling down of suppression pool is started

9:00 Fukushima-Daiichi (1) #2 Water level inside pressure vessel: 390cm above the top of fuel rod

9:05 Fukushima-Daiichi (1) #3 Pressure value inside containment vessel is slightly decreased: 490kPa

10:15 Fukushima-Daini (2) #1 Average water temperature in the suppression chamber decreased to under 100 degree Celcius continuously

11:01 Fukushima-Daiichi (1) #3 Hydrogen explosion is occurred
The top 1/3 of the reactor building is blowen off
11 workers are injured (1 of them is heavily injured)
Pressure value inside containment vessel is stable (the vessel seems to be maintain its soundness)

11:20 Fukushima-Daiichi (1) #3 Water level inside pressure vessel: 180cm under the top of fuel rod
Water pumping is continued

12:00 Fukushima-Daiichi (1) #2 Water level inside pressure vessel: 340cm above the top of fuel rod
TEPCO starts preparation for sea water pumping to #2 reactor

13:25 Fukushima-Daiichi (1) #2 Isolation Cooling System (RCIC) is stopped
All cooling systems are failed

17:00 Fukushima-Daini (2) #1 Reactor is completely stopped

17:16 Fukushima-Daiichi (1) #2 Water level inside pressure vessel: 0cm above the top of fuel rod

18:00 Fukushima-Daini (2) #2 Reactor is completely stopped

18:06 Fukushima-Daiichi (1) #2 Safety Relief Valve (SRV) is opened

18:22 Fukushima-Daiichi (1) #2 Entire fuel rods are no longer soaked by water

18:24 Fukushima-Daiichi (1) #2 Sea water pumping is started


Fukushima-Daiichi (1) #2 Sea water pumping is suspended due to too high pressure inside the core vessel and out of fuel of fire engine

19:53 Fukushima-Daiichi (1) #2 2 SRVs are opened again (additional pressure release)

20:05 Fukushima-Daiichi (1) #2 Sea water pumping is resumed (2 fire engines are used)

20:04 Fukushima-Daiichi (1) #2 Pressure inside core vessel: 0.81MPa
Water level: N/A (too low)
Pressure inside containment vessel: 0.42MPa

21:00 Fukushima-Daiichi (1) Neutron beam is detected at the main gate of the site (0.01?Sv/h)

21:34 Fukushima-Daiichi (1) #2 Water level inside pressure vessel is recovered: 200cm under the top of fuel rod

21:37 Fukushima-Daiichi (1) 3130?Sv/h at the main gate of the site
3/15/2011 23:00 Fukushima-Daiichi (1) #2 Both of SRVs are closed
Pressure inside the core vessel is being increased
Entire fuel rods are no longer soaked by water again

0:00 Fukushima-Daiichi (1) #2 Vent of containment vessel is opened

0:02 Fukushima-Daiichi (1) #2 Another SRVs are opened

1:00 Fukushima-Daiichi (1) #2 TEPCO confirms that SRVs are opend
Sea water pumping is resumed

3:00 Fukushima-Daiichi (1) #2 Entire fuel rods are not soaked by water yet

6:00 Fukushima-Daiichi (1) #4 Explosion sound is confirmed
A hole on the roof of reactor building is found

6:14 Fukushima-Daiichi (1) #2 Explosion sound is confirmed
A deficit of supression pool is found


Fukushima-Daiichi (1) #2 Workers are evacuated except for about 50 people who are in charge of essential work
Water pumping is contuniued

7:05 Fukushima-Daiichi (1) #3 Vapor cloud is observed above the reactor building of #3 plant

7:15 Fukushima-Daini (2) #4 Reactor is completely stopped

8:31 Fukushima-Daiichi (1) 8217?Sv/h at the main gate of the site

9:00 Fukushima-Daiichi (1) 11930?Sv/h at the main gate of the site

9:35 Fukushima-Daiichi (1) 7241?Sv/h at the main gate of the site

9:38 Fukushima-Daiichi (1) #4 Fire is discovered at the operation floor by TEPCO personnel

10:15 Fukushima-Daiichi (1) 8837?Sv/h at the main gate of the site

11:00 Fukushima-Daiichi (1) #4 TEPCO personnel confirmed fire is extinguished spontaneously
-> TEPCO apologizes that this was not surely confirmed (3/16 6:45)

12:15 Fukushima-Daiichi (1) 1407?Sv/h at the main gate of the site

13:00 Fukushima-Daiichi (1) #2 Water level inside pressure vessel is recovered: 170cm under the top of fuel rod

13:50 Fukushima-Daiichi (1) 969.9?Sv/h at the main gate of the site


Fukushima-Daiichi (1) Evacuation from the area within 20km radius from the site is completed

15:20 Fukushima-Daini (2) #1 Increase of temperature of the Emergency Component Cooling Water system is confirmed
Stop the Residual Heat Removal System (B) to make a maitenance of it

16:20 Fukushima-Daiichi (1) 502.6?Sv/h at the main gate of the site

16:25 Fukushima-Daini (2) #1 The battery for The Emergency Component Cooling Water system is replaced and restarted
The Residual Heat Removal System (B) is restarted

20:05 Fukushima-Daini (2) #4 Delivery pressure of the pump for the Residual Heat Removal System (B) is decreased
The Residual Heat Removal System (B) is stopped to have a maintenance

21:00 Fukushima-Daiichi (1) 298.8?Sv/h at the main gate of the site

21:25 Fukushima-Daini (2) #4 The battery for The Emergency Component Cooling Water system is replaced and restarted
The Residual Heat Removal System (B) is restarted

22:00 Fukushima-Daiichi (4) National government orders for TEPCO to inject water into spent fuel pool under the Nuclear Reactor Regulation Law

23:00 Fukushima-Daiichi (1) 4548?Sv/h at the main gate of the site

23:10 Fukushima-Daiichi (1) 6960?Sv/h at the main gate of the site

23:30 Fukushima-Daiichi (1) 8080?Sv/h at the main gate of the site
3/16/2011 7:30 Fukushima-Daiichi (1) 651?Sv/h at the main gate of the site

5:45 Fukushima-Daiichi (1) #4 Fire is occured at the operation floor

6:15 Fukushima-Daiichi (1) #4 Fire is extinguished spontaneously

10:00 Fukushima-Daiichi (1) #3 Vapor cloud is observed above the reactor building of #3 plant
Radiation dose detected at the main gate of the site is being rapidly increased

10:40 Fukushima-Daiichi (1) 10mSv/h at the main gate of the site

11:00 Fukushima-Daiichi (1) #3 Radiation dose detected at the main gate of the site is decreased again: 3.4mSv/h

11:15 Fukushima-Daiichi (1) #3 Secretary of Cabinet Mr. Edano announces that this vapor cloud can be caused by the damage of a part of the containment vessel


Fukushima-Daiichi (1) NISA annouces that any damage of #3 reactor's containment vessel is not confirmed and it can be understood as a result of the vapor leak from #2 plant, according to TEPCO

11:20 Fukushima-Daiichi (1) 2.3mSv/h at the main gate of the site


Fukushima-Daiichi (1) TEPCO begin the efforts to build new power line to the plants
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