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! Concentration (Bq/cm<sup>3</sup>)
! Concentration (Bq/cm<sup>3</sup>)
|-
|-
|{{SimpleNuclide2|Chlorine|38}}
|{{SimpleNuclide2|link=yes|Chlorine|38}}
|1.6·10<sup>6</sup>
|1.6·10<sup>6</sup>
|-
|-
|{{SimpleNuclide2|Arsenic|74}}
|{{SimpleNuclide2|link=yes|Arsenic|74}}
|3.9·10<sup>2</sup>
|3.9·10<sup>2</sup>
|-
|-
|{{SimpleNuclide2|Yttrium|91}}
|{{SimpleNuclide2|link=yes|Yttrium|91}}
|5.2·10<sup>4</sup>
|5.2·10<sup>4</sup>
|-
|-
|{{SimpleNuclide2|Iodine|131}}
|{{SimpleNuclide2|link=yes|Iodine|131}}
|2.1·10<sup>5</sup>
|2.1·10<sup>5</sup>
|-
|-
|{{SimpleNuclide2|Caesium|134}}
|{{SimpleNuclide2|link=yes|Caesium|134}}
|1.6·10<sup>5</sup>
|1.6·10<sup>5</sup>
|-
|-
|{{SimpleNuclide2|Caesium|136}}
|{{SimpleNuclide2|link=yes|Caesium|136}}
|1.7·10<sup>4</sup>
|1.7·10<sup>4</sup>
|-
|-
|{{SimpleNuclide2|Caesium|137}}
|{{SimpleNuclide2|link=yes|Caesium|137}}
|1.8·10<sup>6</sup>
|1.8·10<sup>6</sup>
|-
|-
|{{SimpleNuclide2|Lanthanum|140}}
|{{SimpleNuclide2|link=yes|Lanthanum|140}}
|3.4·10<sup>2</sup>
|3.4·10<sup>2</sup>
|-
|-

Revision as of 20:05, 26 March 2011

See also: 2011 Japanese nuclear incidents, Fukushima I Nuclear Power Plant, Fukushima II Nuclear Power Plant, Fukushima I nuclear accidents, and 2011 Tōhoku earthquake and tsunami
File:Fukushima I by Digital Globe 2 cropped.jpg
During the 2011 Fukushima nuclear emergency in Japan, four nuclear reactors were damaged by explosions.

On 11 March 2011, a 9.0 magnitude earthquake struck off the coast of Japan, off the island of Honshu.[1] This earthquake produced a large tsunami in Japan, and a tsunami warning for over 20 countries. The earthquake triggered the shut down of three of the Fukushima I (Dai-Ichi) Power Plant's six Reactors and all four of the Fukushima II (Dai-Ni) Power Station's four reactor units. The subsequent tsunami stopped Fukushima I station's backup diesel generators. The earthquake and tsunami caused the damage that led to the explosions and partial meltdowns at the Fukushima I facility.

Background

Main article: 2011 Tōhoku earthquake and tsunami
See also: 2011 Japanese nuclear accidents

Fukushima I

Main article: Fukushima I nuclear accidents
See also: Fukushima I Nuclear Power Plant

Fukushima II

Main article: Fukushima II Nuclear Power Plant

Timeline

Times are given in Japan Standard Time (JST), unless noted, which is UTC plus nine hours.

Friday, 11 March

14:46
A 9.0 magnitude earthquake strikes off the coast of Honshu Island at a depth of about 24 kilometres (15 mi). Fukushima I power plant's nuclear reactors 1, 2, and 3 are automatically shut down by the shake. Nuclear reactors 4, 5, and 6 were undergoing routine maintenance and were not operating, (reactor 4 was defueled Nov 2010). The tremor has the additional effect of causing the power plant to be cut off from the Japanese electricity grid, however, backup diesel generators kick in to continue cooling. Tokyo Electric Power Company (TEPCO), the plant's operator, finds that units 1 and 2 are not operating correctly and notifies the proper officials.[2]
15:01 (approximate)
The tsunami unleashed by the earthquake strikes the Fukushima facility damaging the backup generators required to cool the reactors. With the loss of power from the grid and the damage to the generators, the plant has become "dark". Later, reports indicate that only the generator for unit number 6 remained working in full operational capacity.
According to a report in the New York Times, "[A]t the start of the crisis Friday, immediately after the shattering earthquake, Fukushima plant officials focused their attention on a damaged storage pool for spent nuclear fuel at the No. 2 reactor at Fukushima I, said a nuclear executive who requested anonymity.... The damage prompted the plant’s management to divert much of the attention and pumping capacity to that pool, the executive added. The shutdown of the other reactors then proceeded badly, and problems began to cascade."[3]
16:00
The Nuclear and Industrial Safety Agency of Japan initiates an emergency headquarters in an attempt to gather information on the 55 nuclear reactors in Japan.[4] There is no report that radiation was detected outside plant borders.[5]
19:03
Prime Minister Naoto Kan declares a nuclear emergency status.[6] This is announced by Yukio Edano, Chief Cabinet officer in Japan. Japanese government officials try to comfort the people of Japan by telling them that the proper procedures are being undertaken. They also announce that no radioactive leaks have been detected.[4]
21:00
An evacuation order is issued by the government to persons within a 3 kilometres (1.9 mi) radius of the Fukushima I station. Those within a 10 kilometres (6.2 mi) radius are told that they can remain in their homes and carry on with regular activities until told otherwise.[4]
At Fukushima I, the ongoing lack of electricity is causing the cooling system to fail, and the pressure within the nuclear units build up. This pressure buildup is the result of residual decay heat causing the coolant, which is not being circulated, to evaporate.[7] There is no confirmation of radiation leaking from the reactor.[8] TEPCO announces that pressure inside reactor unit 1 of Fukushima I is more than twice normal levels.[4]

Saturday, 12 March

Overview map showing evacuation and other zone progression and selected radiation levels.
02:44
Emergency battery power for the High Pressure Core Flooder System for #3 runs out.
04:15
Fuel rods in #3 are exposed.
04:30
Officials declare a heightened state of alert for Fukushima II (Dai-ni). Officials declare a state of nuclear emergency for Fukushima I (Dai-ichi).[9]
05:30
Despite the high risk of the hydrogen igniting after combining with oxygen in water or the atmosphere, in order to release some of the pressure inside the reactor at Fukushima I unit 1, the decision is taken to vent some of the steam (which contained a small amount of radioactive material) into the air in the metal container building surrounding the unit.
10:09
TEPCO confirms that a small amount of vapor has been released into the air to release pressure in reactor unit 1 (Fukushima I).[10]
10:58
Pressure still remains too high inside reactor unit 2 at Fukushima I. In order to alleviate some of this pressure, a consensus is reached to, once more, vent radioactive vapor into the air.[10]
15:30
Evacuation of residents within 3 km of Fukushima II underway. Evacuation of residents within 10 km of Fukushima I underway.[9]
15:36
Unit 1 at Fukushima I: cameras document a massive hydrogen explosion on the outer structure of one of four buildings at the plant. It also documents the outer structure collapsing.
18:36 (approximately)
TEPCO announces that four persons who are employed at the power plant have been injured in the unit one explosion.
File:2011-03-12 1800 NHK Sōgō channel news program screen shot.jpg
Reactor building#1 at Fukushima I, wrecked by explosion.
20:00
Uncertainty surrounds the actual cause of the blast at Fukushima I (later identified as a hydrogen explosion) and the damage caused.
Yukio Edano announces that the concrete building surrounding the steel reactor container at unit 1 in Fukushima I has collapsed as a result of the explosion; however no damage has been inflicted on the reactor itself.
21:40
Evacuation zone around Fukushima I extended to 20 km. Evacuation zone around Fukushima II extended to 10 km.[9]
To release pressure within the reactor unit 1 at Fukushima I, steam is released out of the unit into the air. This steam contains water vapor, Hydrogen, Oxygen and some radioactive material, mostly tritium and 16N.

Sunday, 13 March

05:10
Fukushima I Unit 1 declared as an INES Level-4 "accident with local consequences" event.[9]
10:35
Fukushima II Unit 3 confirmed as shutdown cold and safe.[9]
At Fukushima II, one worker is confirmed to have died in a crane accident, four other injured.[9]
Fukushima II Units 1, 2, and 4 are being powered by offsite power.[9]

Monday, 14 March

11:15
The outer building surrounding Unit 3 of Fukushima I explodes, presumably due to the ignition of built up hydrogen gas.[11][12] No health risk is reported, though 600 people have been ordered to stay indoors. Chief Cabinet Secretary Yukio Edano reports that "The vessel containing the No. 3 reactor’s radioactive core is intact after yesterday’s blast", and that while the outer reactor building of Unit 3 at Fukushima I is blown apart, the inner containment vessel is not breached. TEPCO later says at least four employees and two contractors were injured in the blast.[13]
11:44
Radiation reading at the Fukushima I Nuclear Power Station (NPS) border is 20 μSv/hour.[14]
12:30
Status of the Fukushima I station at 12:30 on 14 March[14]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service In service In service Defueled Outage (scheduled) Outage (scheduled)
Fuel integrity Damaged Not damaged Damaged Not damaged Not damaged Not damaged
Containment integrity Not damaged Not damaged Not damaged Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional RCIC working Not functional Not necessary Not necessary Not necessary
Building integrity Damaged Not damaged Damaged Not damaged Not damaged Not damaged
Pressure vessel, water level Unknown Above core Unknown Safe Safe Safe
Pressure vessel, pressure Stable Stable Stable Safe Safe Safe
Containment pressure Stable Stable Stable Safe Safe Safe
Seawater injection into core Suspended To be decided Performed Not necessary Not necessary Not necessary
Containment venting Performed Preparing Performed Not necessary Not necessary Not necessary
Environmental effect (NPS border) 20 μSv/hour at 11:44
Evacuation radius 20 km
INES Level 4 (estimated by NISA)
13:15
Fukushima II Unit 1 cooling system has been restored, work continues on units 2 and 4.[9]
13:55
Radiation reading at the Fukushima I Nuclear Power Station (NPS) border is 15 μSv/hour.[15]
20:30
Status of the Fukushima I station at 20:30 on 14 March[15]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service In service In service Defueled Outage (scheduled) Outage (scheduled)
Fuel integrity Damaged Unknown Damaged Not damaged Not damaged Not damaged
Containment integrity Not damaged Not damaged Not damaged Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Building integrity Damaged Not damaged Damaged Not damaged Not damaged Not damaged
Pressure vessel, water level Unknown Low (recovering) Unknown Safe Safe Safe
Pressure vessel, pressure Low Unknown Stable Safe Safe Safe
Containment pressure Stable Increasing Stable Safe Safe Safe
Seawater injection into core Suspended Performed Performed Not necessary Not necessary Not necessary
Containment venting Performed Preparing Performed Not necessary Not necessary Not necessary
Environmental effect (NPS border) 15 μSv/hour at 13:55
Evacuation radius 20 km
INES Level 4 (estimated by NISA)
21:00 (approximate)
Fuel rods within Reactor #2 of the Fukushima I nuclear plant were fully exposed to air (but were still within the intact containment vessel and therefore not exposed to the outer atmosphere). TEPCO earlier said the cooling system had been lost and began injecting seawater into the reactor to cool it down.[16]
21:08
The IAEA announce the temperature in the spent fuel pond of reactor 4 are at 84 °C[9]
21:16
Yukio Edano affirms that Reactor number 2 of Fukushima I is unlikely to explode. In addition, he stated that there is ongoing work to cool down the reactor.[17]
23:20 (approximate)
Fuel rods at Reactor #2 of Fukushima I became fully exposed once again. TEPCO says that pressure inside the reactor rose again because the unit's air flow gauge was accidentally turned off. With the gauge turned off, flow of water into the reactor was blocked, leading to full exposure of the rods.[18]

Tuesday, 15 March

06:00 (approximate)
A fire in unit 4 reportedly breaks out around 6 am[19]
06:14 (approximate)
A third explosion occurs at Fukushima I, unit 2 and damage of the containment building is feared.[20] Reactor unit 2's pressure-suppression system (the torus) is feared damaged, and the radiation level exceeds the legal limit to reach 965.5 µSv/hour. The radiation level later fluctuates up to 8217 µSv/hour, two hours after the explosion. The level goes down to 2400 µSv/hour shortly later.[21][22] Workers at the plant start evacuation, with a select few remaining to keep the reactors cooled.[23] The plant's operator says the nuclear fuel rods could be melting.[22] Additionally, it is confirmed that the 4th floor rooftop area of the Unit 4 Nuclear Reactor Building had sustained damage, likely caused by the earlier blast of Unit 3.[24]
07:00
Status of the Fukushima I station at 07:00 on 15 March
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service In service In service Defueled Outage (scheduled) Outage (scheduled)
Fuel integrity Damaged Damaged Damaged Not damaged Not damaged Not damaged
Containment integrity Not damaged Partly damaged Not damaged Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Building integrity Damaged Partly damaged Damaged Fire in progress Not damaged Not damaged
Pressure vessel, water level Unknown Low (recovering) Unknown Safe Safe Safe
Pressure vessel, pressure Low Leaked Stable Safe Safe Safe
Containment pressure Stable Increasing Stable Safe Safe Safe
Seawater injection into core Suspended Performed Performed Not necessary Not necessary Not necessary
Containment venting Performed Preparing Performed Not necessary Not necessary Not necessary
Environmental effect (NPS border and onsite) 8217 µSv/hour at 08:30,[25][21] and between 100 and 400 mSv/hour at times.[26][27][28]
Evacuation radius 20 km
INES Level 4 (estimated by NISA); Level 6 (estimated by France's Nuclear Safety Authority, ASN)
08:30
Radiation reading at the Fukushima I Nuclear Power Station (NPS) border is 8217 µSv/hour.[25][21]
08:54
A fourth explosion and resulting fire is reported at unit 4.[20] IAEA Reports that initial fire at unit 4 started at 2354 UTC on 14 March.[29]
09:14 (approximate)
MSNBC reports that radiation measurements spiked at 11,900 µSv/hour around 0914 as measured at the front gate of the facility and speculates it was caused by the third explosion at unit 2.[30]
09:40
The Fukushima I Unit 4 building catches fire around 6 am,[19] likely releasing radioactive contamination from the spent fuel stored there.[31][32] TEPCO says workers extinguished the fire by 12:00.[33][34] As radiation levels rise, some of the fifty employees still at the plant are evacuated.[35]
10:22
The Fukushima I radiation monitor readings outside of the buildings are 30 mSv/hour between Unit 2 and Unit 3, 400 mSv/hour beside Unit 3, and 100 mSv/hour beside Unit 4.[19]
11:00 (approximate)
IAEA Reports that initial fire at unit 4 was extinguished at 200 UTC on 15 March.[9]
11:35
At Fukushima II (Dai-Ni), Units 1, 2, and 3 are in cold shutdown. For Unit 4, work is in progress to restore cooling and bring it to cold shutdown.[9]
13:35
No fly zone declared for 30 km around the Fukushima I plant. Prime Minister warns of radiation hazard and further radiation leaks.
16:09
There is a fire at a spent fuel pond of a reactor and radioactivity has been released into the atmosphere, says the IAEA according to AFP news agency.[36]
16:30
Radiation reading at the Fukushima I Nuclear Power Station (NPS) border is 489.8 µSv/hour.[37]
16:38
The AFP reports that the fire previously reported at unit 4's spent fuel pond had released "radioactivity... directly into the atmosphere" according to the IAEA .[36]
17:00
The fire at the spent fuel pond has been put out by Japanese authorities according to the IAEA; they state "Japanese authorities have confirmed that the fire at the spent fuel storage pond at the Unit 4 reactor of Fukushima I nuclear power plant was extinguished on 15 March at 17:00 JST."[9]
17:03
There has been a slight rise in temperature of two more reactors at Fukushima I nuclear plant, the chief government spokesman says according to AFP.[36]
18:00
Japanese nuclear safety official confirms reports that the water inside the waste fuel storage pool for the Unit 4 Fukushima reactor may be boiling, AP reports.[36]
19:00
Status of the Fukushima I station at 19:00 on 15 March[37]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service In service In service Defueled Outage (scheduled) Outage (scheduled)
Fuel integrity Damaged Unknown Damaged Not damaged Not damaged Not damaged
Containment integrity Not damaged Damage suspected Not damaged Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Building integrity Severely Damaged Slightly damaged Severely Damaged Partially Damaged Not damaged Not damaged
Pressure vessel, water level Around half of the fuel Recovering after dried-up Around half of the fuel Safe Safe Safe
Pressure vessel, pressure Stable Fluctuating Stable Safe Safe Safe
Containment pressure Stable D/W: Unknown, S/P: Atmosphere Stable Safe Safe Safe
Seawater injection into core Continuing Continuing Continuing Not necessary Not necessary Not necessary
Seawater injection into containment building Continuing To be decided To be decided Not necessary Not necessary Not necessary
Containment venting Continuing Preparing Continuing Not necessary Not necessary Not necessary
Spent fuel integrity (no data) (no data) (no data) SFP level low, injecting water SFP temperature increasing SFP temperature increasing
Environmental effect (NPS border) 489.8 µSv/hour at 16:30
Evacuation radius 20 km
INES Level 4 (estimated by NISA); Level 6 (estimated by France's Nuclear Safety Authority, ASN)
21:00
The water level in Fukushima I Unit 5 has been decreasing. Workers plan to use Unit 6's diesel generator to help pump water into Unit 5.[9] Japanese authorities have also informed the IAEA that at 12:00 UTC of 15 March the water level in Unit 5 had decreased to 201 cm above the top of the fuel. This was a 40 cm decrease since 07:00 UTC of 15 March. Officials at the plant were planning to use an operational diesel generator in Unit 6 to supply water to Unit 5.[9]
23:35
Radiation reading at the Fukushima I Nuclear Power Station (NPS) border is 6308 µSv/hour.[38]

Wednesday, 16 March

05:45
A location in the building of reactor 4 is reported to be on fire at the Fukushima I (by NHK TV[39]). According to one of the worker's testimony, flames were present at the location of Tuesday's fire. The fire was verified by satellite imagery showing smoke rising from the reactor 4 building. The fire disappeared later.[19] IAEA confirms reports that a fire was visually observed in unit 4, in a similar area as the original fire.[9] This new fire cast into doubt the earlier hope that the Tuesday blaze in the Unit 4 housing was caused by lubricating oil pumps; instead TEPCO officials acknowledge it is possible the spent fuel rods are uncovered and overheating, remarking that "the possibility of a re-criticality is not zero."[39] Iouli Andreev, former director of the Soviet Spetsatom clean-up agency involved in Chernobyl clean-up, and Laurence Williams, professor of nuclear safety at the University of Central Lancashire, speculate that the Fukushima management had engaged in an unsafe practice of re-racking spent rods in the pool well beyond its rated capacity, in effect heightening danger of melting and pool boil-off.[40][41]
06:15
IAEA Reports that the fire previously observed in unit 4 is no longer visible.[9]
07:30
Evacuation of the 20 km zone around Fukushima I is completed.[9]
08:00 (approximately)
The US Embassy in Japan is recommending that all personnel adhere to the Japanese safety measures, "including their recommended 20 km radius for evacuation and additional shelter-in-place recommendations out to 30 km."[42]
08:00
Status of the Fukushima I station at 08:00 on 16 March[38]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service In service In service Defueled Outage (scheduled) Outage (scheduled)
Fuel integrity 70% damaged[43] 33% damaged[43] Damaged Not damaged Not damaged Not damaged
Containment integrity Not damaged Damage suspected Not damaged Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Building integrity Severely damaged Slightly damaged Severely damaged Partially damaged Not damaged Not damaged
Pressure vessel, water level Around half of the fuel Recovering after dried-up Around half of the fuel Safe Safe Safe
Pressure vessel, pressure Stable Fluctuating Stable Safe Safe Safe
Containment pressure Stable D/W: Unknown, S/P: Atmosphere Stable Safe Safe Safe
Seawater injection into core Continuing Continuing Continuing Not necessary Not necessary Not necessary
Seawater injection into containment building Continuing To be decided To be decided Not necessary Not necessary Not necessary
Containment venting Continuing Preparing Continuing Not necessary Not necessary Not necessary
Spent fuel integrity (no data) (no data) (no data) SFP level low SFP level decreasing SFP level decreasing
Environmental effect (NPS border and onsite) 6308 μSv/hour at 23:35, 15 March,[38] with increases to 1,000 mSv/hour early 16 March and then decreasing to 800–600 mSv/hour[44]
Evacuation radius 20 km
INES Level 4 (estimated by NISA); Level 6 (estimated by France's Nuclear Safety Authority, ASN)
08:30
White smoke is seen rising from the vicinity of Fukushima I Unit 3. Damage to the containment vessel of the unit is suspected.[19] Later TEPCO reports that failing to cool the Spent Fuel Pool resulted in evaporation of pool water, which caused steam.[45]
09:00
The fire that broke out inside the building of Fukushima I reactor 4 appears to be extinguished.[36] According to Kyodo News, TEPCO is considering spraying boric acid by helicopter to prevent the spent nuclear fuel rods from reaching criticality again and starting a nuclear chain reaction.[46] However, TEPCO says that readings showed high levels of radiation, making the building inaccessible, and therefore making the spraying "extremely difficult".[36]
10:01 (estimated)
Reactor 3 at Fukushima I nuclear power plant begins emitting white smoke.[36]
10:46
TEPCO says the reactor 3 at Fukushima I nuclear power plant has been emitting white smoke for about 45 minutes.[36]
11:00
Radiation reading at the Fukushima I Nuclear Power Station (NPS) border is 3391 µSv/hour[19]
11:36
The remaining 50 workers located in the Fukushima I nuclear power plant evacuate after radiation levels there surge.[47]
11:40
Chief cabinet secretary Edano announces that the white fumes emerging from the plant may constitute radioactive steam that has breached Fukushima I Unit 3's containment.[48]
12:30
Status of the Fukushima I station at 12:30 on 16 March[19]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service In service In service Defueled Outage (scheduled) Outage (scheduled)
Fuel integrity 70% damaged[43] 33% damaged[43] Damaged Not damaged Not damaged Not damaged
Containment integrity Not damaged Damage suspected Damage suspected Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Building integrity Severely damaged Slightly damaged Severely damaged Severely damaged Not damaged Not damaged
Pressure vessel, water level Around half of the fuel Recovering after dried-up Around half of the fuel Safe Safe Safe
Pressure vessel, pressure Stable Fluctuating Stable Safe Safe Safe
Containment pressure Stable D/W: Unknown, S/P: Atmosphere Stable Safe Safe Safe
Seawater injection into core Continuing Continuing Continuing Not necessary Not necessary Not necessary
Seawater injection into containment building Continuing To be decided To be decided Not necessary Not necessary Not necessary
Containment venting Continuing Preparing Continuing Not necessary Not necessary Not necessary
Spent fuel integrity (no data) (no data) High temperature suspected SFP level low,
Preparing water injection,
Damage to fuel rods suspected 		SFP temperature increasing SFP temperature increasing
Environmental effect (NPS border) 3391 µSv/hour at 11:00, 16 March[19]
Evacuation radius 20 km from Nuclear Power Station (NPS)
INES Level 4 (estimated by Japanese NISA and accepted by the international IAEA); Level 6 (estimated by the French Nuclear Safety Authority, ASN)[49][50][33])
12:35 (approximate)
The 50 personnel that were evacuated at 11:36 return to the facility after radiation levels subside.[51]
14:30
Radiation reading at the Fukushima I Nuclear Power Station (NPS) border is 1937 µSv/hour.[45]
17:26
TEPCO says that work on cooling the Fukushima I reactors is suspended due to radiation risks for the second time.[52]
18:00
Radiation decreased to 1500 µSv/hour at Fukushima I site boundary (NHK TV). See also this map of various detectors stationed around Japan (owned by public and government).
19:00
The Fukushima I Unit 3 Spent Fuel Pool level is low, with preparations for water injection.[45]
19:00
Status of Fukushima I at 19:00 on 16 March[45]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service In service In service Defueled Outage (scheduled) Outage (scheduled)
Fuel integrity 70% damaged[43] 33% damaged[43] Damaged No fuel rods Not damaged Not damaged
Containment integrity Not damaged Damage suspected Damage suspected Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Building integrity Severely damaged Slightly damaged Severely damaged Severely damaged Not damaged Not damaged
Pressure vessel, water level Around half of the fuel Recovering after dried-up Around half of the fuel Safe Safe Safe
Pressure vessel, pressure Stable Fluctuating Stable Safe Safe Safe
Containment pressure Stable D/W: Unknown, S/P: Atmosphere Stable Safe Safe Safe
Seawater injection into core Continuing Continuing Continuing Not necessary Not necessary Not necessary
Seawater injection into containment building Continuing To be decided To be decided Not necessary Not necessary Not necessary
Containment venting Continuing Preparing Continuing Not necessary Not necessary Not necessary
Integrity of fuel in Spent Fuel Pool (SFP) (no data) (no data) SFP level low,
Preparing water injection 		SFP level low,
Preparing water injection,
Damage to fuel rods suspected 		SFP temperature increasing SFP temperature increasing
Environmental effect (NPS border) 1937 µSv/hour at 14:30, 16 March
Evacuation radius 20 km from Nuclear Power Station (NPS). People who live between 20 km to 30 km from the Fukushima I Nuclear Power Station are to stay indoors.
INES Level 4 (estimated by Japanese NISA and accepted by the international IAEA); Level 6 (estimated by the French Nuclear Safety Authority, ASN)[49][50][53]
19:50
Radiation level at Fukushima II reactor (10km south of Fukushima I): 28.6 µSv/hour. ref
21:05
Australian Foreign Minister Kevin Rudd advises Australians to leave Tokyo.[54]
23:30
130 additional people are allowed in the plant as radiation levels fall.[55]
23:55
IAEA Web Site Reports that "Japanese authorities have reported concerns about the condition of the spent nuclear fuel pool at Fukushima I Unit 3 and Unit 4. Japanese Defense Minister Toshimi Kitazawa announced Wednesday that Special Defence Forces helicopters planned to drop water onto Unit 3, and officials are also preparing to spray water into Unit 4 from ground positions, and possibly later into Unit 3. Some debris on the ground from the 14 March explosion at Unit 3 may need to be removed before the spraying can begin."[56]

Thursday, 17 March

01:37
The Australian Department of Foreign Affairs and Trade issues a Travel Advice Bulletin[57] advising Australian travellers to reconsider the need to travel to Tokyo, the surrounding earthquake-affected districts, Chiba, Fukushima, Aomori, Iwate, Nagano, Niigata and Ibaraki prefectures and not to travel to the Fukushima Nuclear Power Plant exclusion zone and Miyagi Prefecture.
03:50
IAEA Director announces he will travel to Japan to "see the situation for himself".[58]
04:00
The US Embassy, on advice from the Nuclear Regulatory Commission, tells Americans to evacuate a radius of "approximately 50 miles (80 km)" from the Fukushima plant.[59]
05:25 (approximately)
The head of the U.S. Nuclear Regulatory Commission, Gregory Jaczko, says that the fuel pool at unit 4 had run dry and as a result, radiation levels at the plant were "extremely high". TEPCO denies that the pool had run dry and said "the condition is stable" at unit 4.[60][61]
09:00
Radiation levels in cities near Fukushima I plant: 13.9 µSv at Fukushima City, 65 km northwest; 2.71 µSv at Kooriyama city, 60 km west; 1.25 µSv at Iwaki city, 40 km southwest.[62]
09:19 (approximate)
Naoki Tsunoda, a TEPCO spokesman, indicates that the new power lines to the plant were almost finished and that officials planned to try it "as soon as possible." Kyodo said that could be as early as Thursday afternoon.[63]
09:48
Japan Ground Self-Defense Force 1st Helicopter Brigade uses two CH-47 helicopters with helicopter buckets to perform water spraying operations on reactor unit 3.[64][65] Japan Atomic Industrial Forum (JAIF) reports that the helicopter had been specially modified with lead shielding to protect the personnel onboard.[66] However, much of the water appeared to be dispersed in the wind before reaching its target.[67]
10:00
Helicopter based spraying operations are halted after 4 water drops were performed on unit 3.[68] Japanese newscaster NHK indicates that spraying operations will continue from the ground and that personnel are monitoring the radiation levels around the base.
10:15
The IAEA releases a summary of all injuries and contaminations due to the situation at the Fukushima I nuclear plant. It indicates that 23 people were injured, more than 20 were contaminated, and 2 are missing.[69]


10:40
JAIF reports that the radiation levels at the main gate are 10 millisieverts per hour.[70]
11:05
The Japanese nuclear safety agency says external power to the plant should partially resume later in the day.[Kyodo News]
11:10
Radiation reading at the Fukushima I Nuclear Power Station (NPS) border is 646 µSv/hour.[71]
12:00
The IAEA announces that the temperature in spent fuel pond at reactor 5 is 64.2 °C and the spent fuel pond at reactor 6 is 62.5 °C[9]
12:07
Cabinet Secretary Edano says Unit 3 is the top priority for cooling efforts [Kyodo News]
16:00
The Japan Times reports that radiation levels at the main gate drop to 1.5 millisieverts per hour. Additionally, after hours of conflicting reports on the cause of the white smoke emitting from unit 3, Chief Cabinet Secretary Yukio Edano corrects an earlier statement and now believes that the smoke is being released from the storage pool at unit 3, and not the containment vessel.[70]
16:00
Status of Fukushima I at 16:00 on 17 March[71]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service In service In service Defueled Outage (scheduled) Outage (scheduled)
Fuel integrity 70% damaged[43] 33% damaged[43] Damaged No fuel rods Not damaged Not damaged
Containment integrity Not damaged Damage suspected Damage suspected, but considered to be unlikely.[70] Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Building integrity Severely damaged Slightly damaged Severely damaged Severely damaged Not damaged Not damaged
Pressure vessel, water level Around half of the fuel Higher than half of the fuel Around half of the fuel Safe Safe Safe
Pressure vessel, pressure Stable Unknown Stable Safe Safe Safe
Containment pressure Stable D/W: Unknown, S/P: Atmosphere Stable Safe Safe Safe
Seawater injection into core Continuing Continuing Continuing Not necessary Not necessary Not necessary
Seawater injection into containment building Continuing To be decided Continuing Not necessary Not necessary Not necessary
Containment venting Continuing Preparing Continuing Not necessary Not necessary Not necessary
Integrity of fuel in Spent Fuel Pool (SFP) (no data) (no data) SFP level low,
Preparing water injection 		SFP level low,
Preparing water injection,
Damage to fuel rods suspected 		SFP temperature increasing SFP temperature increasing
Environmental effect (NPS border) 646 µSv/hour at 11:10, 17 March
Evacuation radius 20 km from Nuclear Power Station (NPS). People who live between 20 km to 30 km from the Fukushima I Nuclear Power Station are to stay indoors.
INES Level 4 (estimated by Japanese NISA and accepted by the international IAEA); Level 6 (estimated by the French Nuclear Safety Authority, ASN)[49][50][53]
17:00
South Korean foreign minister Kim Sung-hwan urges South Koreans in Japan to stay 80 kilometers outside the earthquake-stricken nuclear complex in Fukushima.[72]
17:30
Rewiring unit 2 to the Japanese power grid is completed at 08:30 UTC and IAEA indicates that power will be turned on once the spraying of unit 3 is completed.[73]
19:05
Tokyo Metropolitan Police riot control team begin spraying water to unit 3 with a water cannon truck, Though it did not have enough effect.[74]
19:35
Japan Self-Defence Forces begin spraying water to unit 3 with five airport crash tenders which came from military air fields.[75][76]
22:00
Status of Fukushima I at 22:00 on 17 March[77]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service In service In service Defueled Outage (scheduled) Outage (scheduled)
Fuel integrity 70% damaged[43] 33% damaged[43] Damaged No fuel rods Not damaged Not damaged
Containment integrity Not damaged Damage suspected Damage suspected, but considered to be unlikely.[70] Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Building integrity Severely damaged Slightly damaged Severely damaged Severely damaged Not damaged Not damaged
Pressure vessel, water level Around half of the fuel Higher than half of the fuel Around half of the fuel Safe Safe Safe
Pressure vessel, pressure Stable Unknown Stable Safe Safe Safe
Containment pressure Unknown D/W: Unknown, S/P: Atmosphere Stable Safe Safe Safe
Seawater injection into core Continuing Continuing Continuing Not necessary Not necessary Not necessary
Seawater injection into containment building Continuing To be decided Continuing Not necessary Not necessary Not necessary
Containment venting Continuing Preparing Continuing Not necessary Not necessary Not necessary
Integrity of fuel in Spent Fuel Pool (SFP) (no data) (no data) SFP level low,
Starting water injection 		SFP level low,
Preparing water injection,
Damage to fuel rods suspected 		SFP temperature increasing, 64.2 °C SFP temperature increasing, 62.5 °C
Environmental effect (NPS border) 309 µSv/hour at 15:30, 17 March[78]
Evacuation radius 20 km from Nuclear Power Station (NPS). People who live between 20 km to 30 km from the Fukushima I Nuclear Power Station are to stay indoors.
INES Level 4 (estimated by Japanese NISA and accepted by the international IAEA); Level 6 (estimated by the French Nuclear Safety Authority, ASN)[49][50][53]
20:07
Soldiers finish successfully spraying 30 tons of water from airport crash tenders onto Unit 3, and TEPCO is now evaluating the effectiveness of the operation.[75][76] IAEA indicates that the spraying of water on the Unit 3 reactor building was temporarily stopped.[73]
22:37
Reuters reports that work has started to connect outside power lines to the Fukushima I nuclear power plant. Unit 2 will be the first to receive electricity. The earliest this could happen is Friday.[79]

Friday, 18 March

01:55
Engineers have begun laying power grid cabling to unit 2. Power to unit 2 will be reconnected once the spraying of water on the unit 3 reactor building ceases.[9]
03:00
The IAEA announces the temperature of the spent fuel pool at Unit 5 is 65.5 °C and the temperature of the spent fuel pool at Unit 6 is 62.0 °C, a slight increase since yesterday at Unit 5, and a slight decrease since yesterday at Unit 6.[9]
04:33
BBC reports with reference to UN's nuclear watchdog that reactor 2 is connected to power line.[80] It may allow operators to restart Emergency Core Cooling System and Residual Heat Removal pumps for the reactor.
05:30
TEPCO reports that laying of grid cabling to Unit 2 continues.[9]
The United States Air Force is using a latest Global Hawk unmanned aircraft from Guam to view the reactors.[81][82]
07:20
The Daily Telegraph publishes a photograph of the damaged unit No. 4 at Fukushima I taken by an employee of TEPCO from an Army's UH-60 helicopter. They claim this photo shows that the pool holding the spent fuel rods in unit 4 has boiled dry.[83]
07:30
Radiation reading at the Fukushima I Nuclear Power Station (NPS) border is 271 µSv/hour.[84]
11:00
The United States is sending water pumps to Japan.[85]
14:00
Water dousing resumes on unit 3 by the Japan Self-Defense Forces (SDF). Workers also joined the operation with a fire truck that lent from the U.S. Air Force in Yokota.[86][87]
16:00
Status of Fukushima I at 16:00 on 18 March[88]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service In service In service Defueled Outage (scheduled) Outage (scheduled)
Fuel integrity 70% damaged[43] 33% damaged[43] Damaged No fuel rods Not damaged Not damaged
Pressure vessel integrity Unknown Unknown Unknown Not damaged Not damaged Not damaged
Containment integrity Not damaged Damage suspected Unknown Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Building integrity Severely damaged Slightly damaged Severely damaged Severely damaged Not damaged Not damaged
Pressure vessel, water level Fuel exposed Fuel exposed Fuel exposed Safe Safe Safe
Pressure vessel, pressure Stable Unknown Stable Safe Safe Safe
Containment pressure Unknown Low Low Safe Safe Safe
Seawater injection into core Continuing Continuing Continuing Not necessary Not necessary Not necessary
Seawater injection into containment building Continuing To be decided Continuing Not necessary Not necessary Not necessary
Containment venting Temporarily stopped Temporarily stopped Temporarily stopped Not necessary Not necessary Not necessary
Integrity of fuel in Spent Fuel Pool (SFP) Water injection to be considered (no data) SFP level low,
Water injection continues 		SFP level low,
Preparing water injection,
Hydrogen from SFP exploded 		SFP temperature increasing, 65.5 °C SFP temperature increasing, 62.0 °C
Environmental effect (NPS border) 271 µSv/hour at 7:30, 18 March[84]
Evacuation radius 20 km from Nuclear Power Station (NPS). People who live between 20 km to 30 km from the Fukushima I Nuclear Power Station are to stay indoors.
INES Level 5 (estimated by Japanese NISA and accepted by the international IAEA); Level 6 (estimated by the French Nuclear Safety Authority, ASN)[49][50][53]
16:00
JAIF reports that the most immediate issue is the threat of damage to the fuel rods in the fuel pools outside the containment vessel at Units 1, 2, 3, and 4.[88]
18:40
IAEA raises INES rating from 4 to 5. Radiation reading 1 km from Fukushima I Unit 2 is 292.2 µSv/hour.[89]
22:00
A plume model shows that the movement of the radioactive material is primarily across the ocean.[90]

Saturday, 19 March

00:45
Water dousing resumes on Unit 3 by hyper rescue troop with the cooperation of Tokyo Fire Department.[91]
01:10
Water dousing on unit 3 completed at 01:10.[91]
05:00
AC power source provided by emergency diesel generator becomes available at Units 5 and 6. Cooling of the spent fuel pool started at Unit 5.[92]
08:10
Radiation measured at the west gate of the power station is 830.8 μSv/h.[92]
12:50
Power line is connected to power plant but not activated yet.[93]
19:07
Milk and spinach from areas around power plant have been found with radiation levels exceeding Japan's standards.[94] Japan government halts sales of all food from Fukushima prefecture.
Status of Fukushima I at 22:00 on 19 March[95]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service -> shutdown In service -> shutdown In service -> shutdown Defueled Outage Outage
Fuel integrity 70% damaged[43] 33% damaged[43] Damaged No fuel rods Not damaged Not damaged
Pressure vessel integrity Unknown Unknown Unknown Not damaged Not damaged Not damaged
Containment integrity Not damaged Damage suspected Unknown Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Building integrity Severely damaged Slightly damaged Severely damaged Severely damaged Vent hole opened on rooftop to prevent hydrogen explosion Vent hole opened on rooftop to prevent hydrogen explosion
Pressure vessel, water level Fuel exposed Fuel exposed Fuel exposed Safe Safe Safe
Pressure vessel, pressure Stable Unknown Stable Safe Safe Safe
Containment pressure Unknown Low Low Safe Safe Safe
Seawater injection into core Continuing Continuing Continuing Not necessary Not necessary Not necessary
Seawater injection into containment building Continuing To be decided Continuing Not necessary Not necessary Not necessary
Containment venting Temporarily stopped Temporarily stopped Temporarily stopped Not necessary Not necessary Not necessary
Integrity of fuel in Spent Fuel Pool (SFP) Water injection to be considered (no data) SFP level low,
Water injection continues 		SFP level low,
Preparing water injection,
Hydrogen from SFP exploded 		SFP temperature high, but decreasing SFP temperature increasing
Environmental effect (NPS border) At 15:30, 19 March: 313.1 µSv/hour (West Gate); and 2972 µSv/hour to the North of the Service Building[95]
Evacuation radius 20 km from Nuclear Power Station (NPS). People who live between 20 km to 30 km from the Fukushima I Nuclear Power Station are to stay indoors.
INES Units 1-3, Level 5 (estimated by Japanese NISA and accepted by the international IAEA); Level 6 (estimated by the French Nuclear Safety Authority, ASN);[49][50][53] Unit 4, Level 3.[95]
22:14
Cooling of the spent fuel pool started at Unit 6.[92]
22:21
Radioactive iodine in trace amounts found in tap water in Tokyo and 5 other areas near Fukushima; and caesium-137 trace amounts have been found in Tochigi and Gunma prefectures. The Japanese government says the amounts, though above normal, do not exceed safety limits and should not affect human health.[96]
23:52
Radioactive iodine beyond limit detected in tap water in a town in Fukushima, reports Kyodo News with reference to government.[97]

Sunday, 20 March

03:00
Restored emergency power to the spent fuel pond cooling systems for units 5 and 6 and have brought the unit 5 pond temperature down from 68.8 °C to 43.1 °C and the unit 6 pond temperature down from 67.5 °C to 52 °C as of 03:00 JST.[98]
04:26
"The Nuclear and Industrial Safety Agency said there is some positive progress and engineers at the end may not need to open valves inside the container vessel of the No. 3 reactor to alleviate pressure that is building up",[99] while they were initially planning this action. Such a move, if forced, would release more radioactive steam.
09:00
Spent fuel pond water temperature dropped to 36.1 °C at Unit 5 and 36.6 °C at Unit 6.[92]
16:00
Status of Fukushima I at 16:00 on 20 March[92]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service -> shutdown In service -> shutdown In service -> shutdown Defueled Outage Outage
Fuel integrity 70% damaged[43] 33% damaged[43] Damaged No fuel rods Not damaged Not damaged
Pressure vessel integrity Unknown Unknown Unknown Not damaged Not damaged Not damaged
Containment integrity Not damaged Damage suspected Unknown Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Building integrity Severely damaged Slightly damaged Severely damaged Severely damaged Vent hole opened on rooftop to prevent hydrogen explosion Vent hole opened on rooftop to prevent hydrogen explosion
Pressure vessel, water level Fuel exposed Fuel exposed Fuel exposed Safe Safe Safe
Pressure vessel, pressure Stable Unknown Stable Safe Safe Safe
Containment pressure Unknown Low Stable at higher level after increase Safe Safe Safe
Seawater injection into core Continuing Continuing Continuing Not necessary Not necessary Not necessary
Seawater injection into containment building Continuing To be decided Continuing Not necessary Not necessary Not necessary
Containment venting Temporarily stopped Temporarily stopped Temporarily stopped Not necessary Not necessary Not necessary
Integrity of fuel in Spent Fuel Pool (SFP) Water injection to be considered (no data) SFP level low,
Water injection continuing 		SFP level low,
Water injection continuing,
Hydrogen from SFP exploded 		Pool cooling capability was recovered Pool cooling capability was recovered
Environmental effect (NPS border) At 05:40, 20 March: 269.5 µSv/hour (West Gate); and 3054 µSv/hour to the North of the Service Building (at 15:00, 20 March)
Evacuation radius 20 km from Nuclear Power Station (NPS). People who live between 20 km to 30 km from the Fukushima I Nuclear Power Station are to stay indoors.
INES Units 1-3, Level 5 (estimated by Japanese NISA and accepted by the international IAEA); Level 6 (estimated by the French Nuclear Safety Authority, ASN);[49][50][53] Unit 4, Level 3.[95]

Monday, 21 March

15:55
Grey smoke emitted from the southeast corner of the Reactor Building #3 at the Fukushima I (Daiichi) plant, in the area of the spent fuel pool. TEPCO evacuated the site temporarily.[100][101]
19:00
White smoke emitted from the roof of Reactor Building #2 at the Fukushima I (Daiichi) plant.[102]
20:00
Full scale cooling restored for the Reactor #5.[103]
23:45
Investigators and researchers in Japan criticized the lack of data on radioactive releases, making it difficult to predict the path of dispersal.[104]

Tuesday, 22 March

2:32
TEPCO has issued[105] a statement that a 0.5 litre sample of sea water 'in the vicinity of the outlet [of the plant]' has revealed an iodine-131 increase of 126.7 times 'above standard levels', among increases of other isotopes.
10:00
TEPCO status report
Status of Fukushima I at 10:00 on 22 March[106]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service -> shutdown In service -> shutdown In service -> shutdown Defueled Outage Outage
Fuel integrity 70% damaged[43] 33% damaged[43] Damaged No fuel rods Not damaged Not damaged
Pressure vessel integrity Unknown Unknown Unknown Not damaged Not damaged Not damaged
Containment integrity Not damaged Damage suspected Unknown Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Not necessary Not necessary
Building integrity Severely damaged Slightly damaged Severely damaged Severely damaged Vent hole opened on rooftop to prevent hydrogen explosion Vent hole opened on rooftop to prevent hydrogen explosion
Reactor pressure vessel, water level Fuel exposed Fuel exposed Fuel exposed Safe Safe Safe
Reactor pressure vessel, pressure Stable Unknown Unknown Safe Safe Safe
Containment pressure Unknown Low Low (after 20 Mar. increase) Safe Safe Safe
Seawater injection into core Continuing Continuing Continuing Not necessary Not necessary Not necessary
Seawater injection into containment building Continuing To be decided Continuing Not necessary Not necessary Not necessary
Containment venting Temporarily stopped Temporarily stopped Temporarily stopped Not necessary Not necessary Not necessary
Integrity of fuel in Spent Fuel Pool (SFP) Water injection to be considered Seawater Injection conducted on 20 Mar. Water level low,
Water injection continuing,
effectiveness has been confirmed 		Water level low,
Water injection continuing,
Hydrogen from SFP exploded 		Pool cooling capability was recovered Pool cooling capability was recovered
Environmental effect (NPS border)

The Main Gate: 264.6 µSv/h at 06:00, 22 Mar.. 　　　　　　North of Service Building: 2015.0 µSv/h at 16:30, 21 Mar.. 161 µSv/h in the town of Namie, Fukushima Prefecture, 20 km from the power plant.
Radio nuclides exceeding the national regulatory standard were detected in milk produced in Fukushima prefecture and spinach from Ibaraki, Fukushima, Tochigi, and Gunma prefectures.

Evacuation radius 20 km from Nuclear Power Station (NPS). People who live between 20 km to 30 km from the Fukushima I Nuclear Power Station are to stay indoors.
INES Units 1-3, Level 5 (estimated by Japanese NISA and accepted by the international IAEA); Level 6 (estimated by the French Nuclear Safety Authority, ASN);[49][50][53] Unit 4, Level 3.[95]
Remarks Immediate threat is damage to fuel in the spent fuel pool (SFP), which is outside the containment vessel. Spraying water onto the SFPs in Units 3 and 4 is continuing. Reductions in ambient radiation around the plant suggest that this spraying has been effective in cooling down the SFPs.

Seawater injection to the Unit 2 fuel pool was conducted on 20 Mar.. Work to recover grid power for the entire plant is in progress.　 So far power has been restored to the distribution switchboard for Unit 2. Integrity checks of electrical equipment in Unit 2 are in progress; these must be completed before the equipment can be energized. 　Grid power has also been partly restored to Unit 5 (which continues to run from its emergency diesel generators). Radiological screening dairy and agricultural products, such as milk in Fukushima and spinach in Ibaraki prefectures, revealed levels of radioisotopes in excess of national regulatory standards. Shipment of these products has been restricted until further notice. Seawater sampled at the front coast of the station contained radioactive iodine (131I) and cesium (134Cs and 137Cs) levels exceeding the regulatory limit. Data collected by an IAEA team show radiation levels of 161 µSv/h in the town of Namie, Fukushima Prefecture, 20 km from the power plant. This level is 1,600 times higher than normal.[107] The worldwide average background dose for a human being is about 2.4 mSv/year (0.27 µSv/h), which is 590 times less than 161 µSv/h.[108]

Wednesday, 23 March

00:34
The BBC reported that external power cables were connected to all units at Fukushima I nuclear power plant and lighting was back on again in the control room of unit 3.[109]
10:15
MSNBC reports that at some point over the prior 24 hour period, "emergency crews dumped 18 tons of seawater into nearly boiling storage pool holding spent nuclear fuel at Unit 2, cooling it to 105 °F (41 °C)".[110]
19:00
Reported I-131 plume across Pacific ocean and USA. Data collected by CTBTO and reported by ZAMG . [111]
21:00
TEPCO status report
Status of Fukushima I at 21:00 on 23 March[112]
Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service -> shutdown In service -> shutdown In service -> shutdown Outage Outage Outage
Core and Fuel Integrity (Loaded fuel assemblies) Damaged (400) Damaged (548) Damaged (548) No fuel rods Not damaged (548) Not damaged (764)
Pressure vessel integrity Unknown Unknown Unknown Not damaged Not damaged Not damaged
Containment integrity Not damaged Damage suspected Might be ”Not damaged” Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Functional Functional
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Functioning (in cold shutdown) Functioning (in cold shutdown)
Building integrity Severely damaged Slightly damaged Severely damaged Severely damaged Vent hole opened on rooftop to prevent hydrogen explosion Vent hole opened on rooftop to prevent hydrogen explosion
Reactor pressure vessel, water level Fuel exposed Fuel exposed Fuel exposed Safe Safe Safe
Reactor pressure vessel, pressure Stable Unknown Unknown Safe Safe Safe
Containment pressure Stable Stable Decreasing after Mar. 20th increase Safe Safe Safe
Seawater injection into core Continuing Continuing Continuing Not necessary Not necessary Not necessary
Seawater injection into containment building (confirming) To be decided (confirming) Not necessary Not necessary Not necessary
Containment venting Temporarily stopped Temporarily stopped Temporarily stopped Not necessary Not necessary Not necessary
Integrity of fuel in Spent Fuel Pool (Stored spent fuel assemblies) Unknown (292) Unknown (587) Possibly damaged (514) Possibly damaged (1331) Not Damaged (946) Not Damaged (876)
Cooling of the Spent Fuel Pool (SFP) Water injection to be considered Seawater Injection conducted on Mar. 20th Water level low,
Water injection continuing,
effectiveness has been confirmed 		Water level low,
Water injection continuing,
Hydrogen from SFP exploded 		Pool cooling capability was recovered Pool cooling capability was recovered
Main Control Room Habitability & Operability Poor due to loss of AC power Poor due to loss of AC power Poor due to loss of AC power (Lighting has been recovered) Poor due to loss of AC power (Lighting has been recovered) Not damaged (estimate) Not damaged (estimate)
Environmental effect (NPS border)

The Main Gate: 265.4 µSv/h at 15:00, Mar. 23. Radioactive nuclides exceeding the legal standard were detected in milk produced in Fukushima and Ibaraki prefectures and spinach and some other vegetables produced in Fukushima, Ibaraki and other prefectures. Also, radioactive Iodine exceeding the standard set by Nuclear Safety Commission was detected in tap water in Fukushima prefecture. The level of the radioactivity detected is low enough not to do harm to the health of people who take those products or water for a limited time. Monitoring results of seawater sampled at coasts in the surrounding area of the station showed that radioactive Iodine, I-131, and Cesium, Cs-134, 137, exceeding the regulatory limit were detected.

Evacuation radius 20 km from Nuclear Power Station (NPS). People who live between 20 km to 30 km from the Fukushima I Nuclear Power Station are to stay indoors.
INES (estimated by NISA) Level 5 Level 5 Level 5 Level 3 - -
Remarks Immediate threat is damage of the fuels in the fuel pool outside the containment vessel. The operation for spraying water to the pool is continuing at Unit 3 and 4.

Work to recover AC power for Unit 1 through 6 is in progress. External AC power has reached to Unit 2, 4, 5 and 6 and is now available in all the units. Integrity check of electric equipment is going on in each unit, which must be done before energizing them. Lighting has been recovered at Unit 3 Main Control Room. External AC power has replaced with the emergency diesel generator in Unit 5 and 6.

Thursday, 24 March

12:10
Three workers were exposed to radiation in the underground of No. 3 reactor's turbine building, and two of them were hospitalized due to radiation burns to their legs, after standing in a puddle of contaminated water.[113] The amount of radioactivity in the water was about 3.9 MBq per cubic centimetre (0.105 Ci/litre).[114] The three workers were exposed to radiation amounting to 173 to 180 millisieverts - exposure to 250 millisieverts is the limit set for workers dealing with the ongoing crisis. They were not wearing protective boots, as their employing firm's safety manuals "did not assume a scenario in which its employees would carry out work standing in water at a nuclear power plant". Two of the workers have likely suffered internal exposure.[115]

Friday, 25 March

Units 1, 2 and 3 had possible breaches in their containment vessels. NISA announced that a breach had likely occurred in the containment vessel of the unit 3 reactor, the only one using a plutonium fuel mix (MOX). Officials suspected it was leaking radiation. Kyodo News reported highly radioactive water was found in the turbine buildings of unit 1 and 2.[116]

US Navy began the transport by barge of 1,890 cubic meters (500,000 gallons) of fresh cooling water to the Fukushima reactors. This fresh water supply is expected to arrive on site within two days.[117]

Japan announced transportation would be provided in a voluntary evacuation zone of 30 kilometres (19 mi).

Tap water was reported to be safe for infants in Tokyo and Chiba but still exceeded limits in Hitachi and Tokaimura.[118]

An analysis of stagnant water in the basement floor of the turbine building of Unit 1 showed heavy contamination.[119]

Analysis results
Nuclide Concentration (Bq/cm3)
38
Cl
 		1.6·106
74
As
 		3.9·102
91
Y
 		5.2·104
131
I
 		2.1·105
134
Cs
 		1.6·105
136
Cs
 		1.7·104
137
Cs
 		1.8·106
140
La
 		3.4·102

Saturday, 26 March

Replacing seawater with fresh water for cooling became a priority due to worries that the salt in the seawater was clogging pipes and coating fuel rods, which may have been hindering the cooling process. [120]

See also

References

  1. ^ "Magnitude 9.0 - NEAR THE EAST COAST OF HONSHU, JAPAN". Earthquake.usgs.gov. Retrieved 17 March 2011.
  2. ^ Josef Oehmen (15 March 2011). "Fukushima Nuclear Accident – a simple and accurate explanation". theenergycollective.com. Retrieved 15 March 2011.
  3. ^ "In Stricken Fuel-Cooling Pools, a Danger for the Longer Term". New York Times. Retrieved 14 March 2011.
  4. ^ a b c d "Timeline: Japan power plant crisis". 13 March 2011. Retrieved 15 March 2011.
  5. ^ "Earthquake Report 2" (PDF). JAIF. 11 March 2011.
  6. ^ "Declaration of Nuclear Emergency" (PDF). Cabinet Secretariat, Cabinet Public Relations Office. Retrieved 14 March 2011.
  7. ^ Gary Anderson (13 March 2011). "Japan earthquake and tsunami: Sea water bid to halt meltdown at Fukushima nuclear plant". mirror.co.uk. Retrieved 15 March 2011.
  8. ^ "Quake Triggers Evacuation of Residents Surrounding Fukushima-1 NPS" (PDF). JAIF. 11 March 2011.
  9. ^ a b c d e f g h i j k l m n o p q r s t u "IAEA Update on Japan Earthquake". IAEA. March 2011.
  10. ^ a b "Timeline: Japan power plant crisis". BBC News. Retrieved 15 March 2011.
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37°25′17″N 141°1′57″E / 37.42139°N 141.03250°E / 37.42139; 141.03250

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