As of 15:00
on July 31, 2011
Nuclear Power Stations' Response to the Off the Pacific Coast of
Tohoku Earthquake
1. Effects on nuclear power stations immediately after the earthquake(1) Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Station(hereafter referred to as “1F”)
Unit-1～3: Automatic shutdown triggered by the earthquake(Unit-1 : 460,000kWe, Unit-2 and 3 : 784,000kWe)
Unit-4～6: In outage shutdown(Unit-4 and 5 : 784,000kWe, Unit-6 : 1.1 million kWe)
(2) Tokyo Electric Power Company's Fukushima Daini Nuclear Power Station(hereafter referred to as “2F”)
Unit-1～4: Automatic shutdown triggered by the earthquake(Unit-1～4 : 1.1 million kWe)
(3) Tohoku Electric Power Company's Onagawa Nuclear Power Station (hereafterreferred to as “Onagawa NPS”)
Unit-1～3: Automatic shutdown triggered by the earthquake(Unit-1 : 524,000kWe, Unit-2 and 3 : 825,000kWe)
Acceleration of 567.5 gal was measured.
(4) Tohoku Electric Power Company's Higashidori Nuclear Power Station (hereafterreferred to as “Higashidori NPS”)
Unit-1: In outage shutdown (Unit-1 : 1.1 million kWe)
Acceleration of 17 gal was measured.
(5) Japan Atomic Power Company's Tokai Daini Nuclear Power Station (hereafterreferred to as “Tokai No.2”)
Automatic shutdown triggered by the earthquake (1.1 million kWe)
2. Nuclear power stations' response after the earthquake(adapted from news statements of the prime minister’s office, Nuclear andIndustrial Safety Agency (NISA) and TEPCO)(1) Tokyo Electric Power Company's 1F
March 11 (Fri)
14：46 The earthquake automatically shut down the unit-1～3.
15：42 Confirmed conditions of unit-1～3 should be reported under Article 10 of
the Act on Special Measures Concerning Nuclear Emergency
Preparedness (hereafter referred to as “Nuclear Emergency Preparedness
Act”)(Due to the complete loss of A/C power; although the loss of off-site
power led to the automatic startup of emergency diesel generators, but
the generators failed.)
15：45 Oil tanks were lost in Tsunami (according to the prime minister's office).
16：36 Confirmed conditions of unit-1 and 2 should be reported under Article 15of the Nuclear Emergency Preparedness Act.
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(Due to loss of the emergency core cooling system's coolant injection
function; coolant injection into unit-1 and 2 could not be confirmed,
leading to taking a precautionary report)
19：03 Declaration of nuclear emergency(Nuclear emergency was declared as the reactor water level at unit-1 and2 could not be confirmed, suggesting the loss of reactor coolant.)
20：50 Fukushima Emergency Headquarters instructed the evacuation to local
residents within 2km radius of 1F (1,864 people in residence within the
2km radius)
21：23 According to Article 15 Paragraph 3 of the Nuclear Emergency
Preparedness Act, the government instructed the evacuation of local
residents within 3km radius of 1F. Residents within 10km radius were
instructed to stay in-house.
March 12 (Sat)01:20 Confirmed conditions of unit-1 should be reported under Article 15 of the
Nuclear Emergency Preparedness Act. (Due to unusual rise of thepressure in PCV)
05：44 The prime minister instructed the evacuation of local residents within
10km radius of 1F.
06：50 According to Article 64 Paragraph 3 of the Act on the Regulation of Nuclear
Source Material, Nuclear Fuel Material and Reactors (hereafter referred toas “Nuclear Reactor Regulation Act”), the Nuclear and Industrial Safety
Agency (hereafter referred to as “NISA”) ordered to implement measures
to reduce the pressure of the reactor containment vessel at unit-1 and 2.
15：36 Hydrogen explosion was occurred at unit-1.
(Loss of upper external walls and ceiling of the reactor building of unit-1)
16：17 Confirmed conditions of 1F should be reported under Article 15 of the
Nuclear Emergency Preparedness Act.(Due to the radiation dose near
1F’s No.4 monitoring post (hereafter referred to as “MP”) exceeded thecriteria (500μSv/h)).
18：25 The prime minister instructed the evacuation of local residents within
20km radius of 1F.
20：05 NISA ordered the injection of sea water to unit-1 according to Article 64
Paragraph 3 of the Nuclear Reactor Regulation Act.
20：20 The injection of sea water and boric acid to unit-1 was commenced.
March 13 (Sun)05：10 Confirmed conditions of unit-3 should be reported under Article 15 of the
Nuclear Emergency Preparedness Act.
(Due to loss of the emergency core cooling system's coolant injection
function; the complete loss of the coolant injection function at unit-3)
08：56 Confirmed conditions of 1F should be reported under Article 15 of the
Nuclear Emergency Preparedness Act.(MP4)(Due to the radiation dose at the site's boundary exceeding the criteria[500μSv/h])2

09：20 Ventilation was achieved at unit-3. (Ventilation valves were operated tocomplete the depressurization measure at 8:41.)

09:25 Unit-3 Began injecting fresh water containing boron into reactor
from fire extinguishing system line.
09：30 According to the Nuclear Emergency Preparedness Act, the prime minister
instructed the content of decontamination screening.
13：12 Injection was switched from fresh water to sea water at unit-3 and beganboron injection.
14：15 Confirmed conditions of 1F should be reported under Article 15 of the
Nuclear Emergency Preparedness Act.(MP4)（Due to the radiation dose at
the site's boundary exceeding the criteria [500μSv/h])March 14 (Mon)
01：00 Seawater injection into the pressure vessel ofunit-1 and unit-3 wassuspended.
03：20 Seawater injection into the pressure vessel of unit-3 was resumed.
03：50 Confirmed conditions of 1F should be reported under Article 15 of the
Nuclear Emergency Preparedness Act (around MP6). (Due to the radiationdose at the site's boundary exceeding the criteria [500μSv/h])
04：15 Confirmed conditions of 1F should be reported under Article 15 of the
Nuclear Emergency Preparedness Act (around MP2). (Due to the radiationdose at the site's boundary exceeding the criteria [500μSv/h])
06：10 Drywell pressure of unit-3 rose to around 460KPa (maximum design
operating pressure: 427KPa)
06：50 Containment vessel pressure of unit-3 rose to 530KPa.
07：44 Confirmed conditions of unit-3 should be reported under Article 15 of the
Nuclear Emergency Preparedness Act. (Due to unusual rise of thepressure in PCV)
09：05 Containment vessel pressure of unit-3 gradually decreased to 490KPa.
09：27 Confirmed conditions of 1F should be reported under Article 15 of the
Nuclear Emergency Preparedness Act. (MP6) （Due to the radiation doseat the site's boundary exceeding the criteria [500μSv/h])
11：01 There was an explosion in unit-3.
13：25 Confirmed conditions of unit-2 should be reported under Article 15 of the
Nuclear Emergency Preparedness Act.
(Due to the loss of reactor cooling function)
18：22 The reactor water level at unit-2 reached -3700mm, indicating that fuelrods were fully exposed.
21：37 Confirmed conditions of 1F should be reported under Article 15 of the
Nuclear Emergency Preparedness Act. (around the station's main gate).
(Due to the radiation dose at the site's boundary exceeding the criteria[500μSv/h])
22：50 Confirmed condition of unit-2 should be reported under Article 15 of the
Nuclear Emergency Preparedness Act.
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(Due to unusual rise of the pressure in PCV)
March 15 (Tue)
06：10 An odd noise was heard from around suppression chamber at unit-2,
followed by a drop in the chamber's pressure, suggesting thedevelopment of an abnormal event at the chamber.
06：14 Loud noise left holes in the walls at unit-4.
Smoke was rising from unit-3.
06：51 Confirmed conditions of 1F should be reported under Article 15 of the
Nuclear Emergency Preparedness Act. (around the station's main gate).
(Due to the radiation dose at the site's boundary exceeding the criteria[500μSv/h])
06：56 The top of the reactor building of unit-4 appeared disfigured.
08：11 Confirmed conditions of 1F should be reported under Article 15 of the
Nuclear Emergency Preparedness Act. (around the station's main gate).
(Due to the radiation dose at the site's boundary exceeding the criteria[500μSv/h])
08：25 Identified white smoke was rising from the 5th floor of unit-2's reactor
building.
09：38 Detected fire at the northwest corner of the 3rd floor of unit-4's reactor
building, and reported to the fire department.
10：01 The Ministry of Economy, Trade and Industry asked the U.S. military toengage in a fire-fighting operation at unit-4.
10：22 The radiation levels were 30mSV/h at the point between unit-2 and unit-3,
400mSV/h around unit-3 and 100mSV/h around unit-4 respectively.
10：59 An evacuation order was issued to the staff of 1F offsite center.
11：26 The stuff of 1F offsite center had evacuated to the Fukushima prefectural
government building.
12：25 The fire extinguishment at unit-4 was confirmed. (Visual confirmationfrom outside due to the inability to enter the building)
16：17 Confirmed conditions of 1F should be reported under Article 15 of the
Nuclear Emergency Preparedness Act. (around the station's main gate)(Due to the radiation dose at the site's boundary exceeding the criteria[500μSv/h])
23：05 Confirmed conditions of 1F should be reported under Article 15 of the
Nuclear Emergency Preparedness Act. (around the station's main gate)(Due to the radiation dose at the site's boundary exceeding the criteria[500μSv/h])March 16 (Wed)05：45 Detected fire at the northwest corner of the 3rd floor of the reactor
building at unit-4.
06：20 TEPCO reported the fire at unit-4 to the local fire department.
08：34 Observed large amount of white smoke rising from unit-3.
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11：14 It was suspected that the white smoke from unit-3 was due to a large
volume of steam rising from the spent fuel storage pool.
March 17 (Thu)
09：48 Unit-3 dousing of seawater drop operation by Self-Defence
Force(hereafter referred to as “SDF”) helicopters (4 times) (～10:00) .
19：05 Unit-3 dousing of seawater by Police’s water cannon truck (once) (～19:15).
19：35 Unit-3 dousing of seawater SDF used fire trucks (5 times) (～20:09).
（Radiation doses before and after the operation: 3,630⇒3,586μSv/h）March 18 (Fri)10:00 Confirmed the shared spent fuel pool is full (temperature: 55 C). In
addition, the exterior visual inspection of the dry cask building found no
anomalies.
13:30 Completed the work for making hole opening on unit-5.
Around 14:00 1F Unit-3 dousing with the fire trucks by SDF (7 times) (~14:38)
14:42 Unit-3 dousing by U.S. Forces’ high pressure water cannons operated by
TEPCO. (~14:45)
17:00 Completed the work for making holes on unit-6.
17:48 NISA announced the results of temporarily rates of INES (International
Nuclear and Radiological Event Scale).
・ Units-1, 2, 3: Level 5 (Accident with wider consequences)
・ Unit 4 : Level 3 (Serious incident)
March 19 (Sat)00:30 Unit-3 continuous dousing by fire trucks of Hyper Rescue Unit of Tokyo
Fire Department (hereafter referred to as “HRU”) (~ 00:50)
05:00 Unit-5 cooling of the spent fuel pool started as C-RHR pump operation had
been resumed.
07:42 The power source of units-5 and 6 were secured as unit-6 two emergency
diesel generators became operable.
08:58 Confirmed conditions of 1F should be reported under Article 15 of the
Nuclear Emergency Preparedness Act.（around the station's west gate）（Due to the radiation dose at the site's boundary exceeding the criteria[500μSv/h]）
09:15 Completed the work for making 3 holes each on the roofs of unit-5 and 6’sreactor buildings for preventing hydrogen gas retention.
14:05 Unit-3 continuous dousing of seawater by HRU (~ 03:40 on March 20)(Radiation dose before and after the operation :3,417⇒2,758 μSv/h)
18:30 Unit-5 spent fuel pool temperature dropped.
(68.8C (06:00 on March 19) => 48.1C (18:00))
22:14 Unit-6 cooling of the spent fuel pool started as C-RHR pump operation had
been resumed.
March 20 (Sun)03:00 Unit-6 spent fuel pool temperature dropped.
(67.5 C (19th 23:00) => 52.0 C (03:00))
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08:00 Unit-3 core temperature was above 300 C, core pressure becoming high.
(reactor temperature under normal operation: 280 to 290 C)
08:20 Unit-4 was doused with 10 fire trucks by SDF (80 t) (~09:29).
14:30 Unit-5 in the state of cold shutdown (reactor water below 100 C)
15:05 Unit-2 was doused the fire trucks by TEPCO (approx. 40t) (~17:20).
18:22 Unit-4 was doused 10 fire trucks by SDF (80 t) (～19:43).
19:27 Unit-6 in the state of cold shutdown (reactor water below 100 C)
21:30 Unit-3 continuous dousing of seawater with the fire trucks by HRU(approx. 1,137 t) (until 03:58 on March 21).
March 21 (Mon)
06:37 Unit-4 dousing with the 12 fire trucks by SDF and U.S. forces highpressure water cannons operated by TEPCO (13 times, approx. 90t) (~08:41).
Radiation dose before and after the operation: (2,319 => 2,126μSv/h）
10:37 Injection of water to the Common Spent Fuel Pool with the fire trucks by
TEPCO (approx. 130t) (~ 15:30).
14:30 Seawater sampling nuclide analysis around unit 1-4 discharge channel(south side) found radioactive nuclides.
15:55 Slightly grayish smoke was observed rising from unit-3 .
16:49 No change of amount of smoke from 1F Unit-3, color changed from grayto white.
18:02 Confirmed the Unit-3 smoke has calmed down.
18:22 White haze like smoke observed rising from unit-2.
March 22 (Tue)
15:10 Unit-3 continuous dousing of seawater by HRU’s fire trucks(approx. 150 t) (~16:00).
16：19 Unit-2 dousing of seawater with the fire truck by TEPCO(approx. 18t)(~17:01).Temperature of the spent fuel pool before and after the dousing(53C=>51C)
17:17 Unit-4 dousing of seawater with the concrete pump truck by TEPCO(approx. 150 t) (~20:32)
19:41 Completed switching to external power supply on 1F units-5 and 6
22:46 Lighting in the central operation room was recovered on 1F unit-3.
March 23 (Wed)02：33 Fire extinguishing line was connected to water injection line for unit-1
reactor pressure vessel.
09：00 The reactor pressure vessel injection line was switched to the water
injection line only (shutting down the fire extinguishing system line) atunit-1.
10:00 Unit-4 dousing of seawater with concrete pump truck by TEPCO(approx.125 t) (~13:02).
Dose rate before and after the dousing (211.49=>224.1μSv/h)
11：00 Unit-3 injection of seawater to spent fuel pool via cleanup water system
by TEPCO (approx. 35t) (~13:20)
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16：20 Unit-3 generating black smoke .(Around 23:30, a TEPCO employee
confirmed that the smoke had ceased.)
17：24 The residual heat removal system seawater pump shut down
automatically when power supply was switched from the temporary to
the permanent on unit-5. (planned to be replaced by a spare pump on
March 24)
March 24 (Thu)
05：35 Unit-3 injecting seawater to the spent fuel pool via cleanup water system
had been resumed by TEPCO.( approx. 120t)(～16:05)
Around 10：50 White hazy steam was found rising from the top of the reactor
building at unit-1
Around 11:30 Lighting in the central operation room was recovered on unit-1.
14：25 Water (reportedly around 3-5cm deep) near the power supply panel for thehigh-pressure condensate pump in the basement of ｕnit-3 turbine
building registered the dose of 200mSv.
14：36 Unit-4 dousing of seawater with concrete pump trucks by TEPCO (approx.
150t) (~17:30)
15：37 External power supply for the common spent fuel pool was resumed.
16：35 Replacing the failed RHRS motor(s) to start operation at unit-5
18：05 Activated the cooling water pump for the common spent fuel pool
March 25(Fri)
06：05 Unit-4 Injection of sea water into spent fuel pool by TEPCO (coolant
purifier system) (-10:20)
08：30 Seawater sampled (at the time indicated to the left) near the unit-1's
south discharge canal was put to nuclide analysis and found to contain
I(iodine)-131 at the density approx. 1250 times the statutory limit
stipulated in the Notification of the Nuclear Reactor Regulation (around 12
times the figure detected on the previous day).
09：00 Traces of water were found indicating that water from the ｕnit-2 reactor
building may have flown from a loading entrance into the generaldischarge canal. (The traces indicate that water may have flown from theloading entrance to the discharge canal, but there was no actual water flow
as of the evening of March 26.)
10：30 Unit-2 injection seawater to the spent fuel pool via cleanup water system
had been resumed by TEPCO. (~12:19).
11：00 The switchover from seawater to freshwater (from a pure water tank)commenced in the water injection operation for unit-1, unit-2 and unit-3.
(The operation must be suspended if there is any deep puddle of water onsite.)
13：28 Unit-3 dousing of seawater with the fire trucks by the Kawasaki City Fire
Department's emergency squad (approx. 450 t) (~16:00).
15：37 Unit-1 injection of freshwater to the reactor had been commenced.

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15:38,15：47 Power supply for the two temporary pumps in the residual heatremoval seawater system of 1F Unit-6 was switched from the temporary to
the permanent.
18：02 Unit-3 Injection of freshwater to the reactor had been commenced.
19：05 Unit-4 Dousing of seawater with the concrete pump trucks by TEPCO(approx. 150 t) (~22:07).
23：10 3.8 million Bq of radioactivity was detected from puddles of water on thefirst floor of the turbine building on unit-1.
＊Results of contamination check of water in the basement of the turbine
building on unit-1
Cl（chlorine）-38
Density：1.6×105Bq/cm3
As（arsenic）-74
Density：3.9×102Bq/cm3
Y（yttrium）-91
Density：5.2×104Bq/cm3
I（iodine）-131
Density：2.1×105Bq/cm3
Cs（caesium）-134
Density：1.6×105Bq/cm3
Cs（caesium）-136
Density：1.7×104Bq/cm3
Cs（caesium）-137
Density：1.8×106Bq/cm3
La（lanthanum）-140 Density：3.4×102Bq/cm3
March 26 (Sat)10：10 Unit-2 Injection of freshwater to the reactor had been commenced.
14：30 Seawater sampled (at the time indicated to the left) near the south
discharge canal of unit-1 was put to nuclide analysis and found to contain
I(iodine)-131 at the density approx. 1850 times the statutory limit
stipulated in the Notification of the Nuclear Reactor Regulation (around 1.5
times the figure detected on the previous day).
16：46 Lighting in the central operation room was recovered on unit-2.
March 27 (Sun)TEPCO announced that the radiation dose rate in excess of 1,000mSv/h
was detected in the surface of water taken from puddles in the turbine
building at unit-2 on March 26. Of nuclides detected in the contaminatedwater, iodine-134 had the density (2.9 x 109Bq/cm3) approx. 10 million
times its usual level in reactor core water.
07：30 Current treatment of puddles of water in the turbine buildings:
・unit-1： Being transported to the condenser
・unit-2： Being prepared for transportation to the condenser
・unit-3 and unit-4： Being considered for transportation to the condenser
12：34 Unit-3 Injection of seawater to the spent fuel storage pool with theconcrete pump trucks by TEPCO (approx. 100 t) (~14:36)
15：30 The water was confirmed to be collected in the vertical parts of the trenches
outside of turbine buildings of units-1 to-3. The dose rates on the water
surface were 0.4 mSv/h at unit-1, over 1,000 mSv/h at unit-2 and notmeasurable at unit-3 because of the rubble.
16：55 Unit-4 Injection of seawater to the spent fuel storage pool with concrete
pump trucks by TEPCO (approx. 125 t) (~19:25)
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18：31 The pump for the fresh water injection to RPV of unit-2 was switched fromthe fire pump trucks to the temporary motor-driven pump. The source ofwater was also switched from a temporary tank to a pure water tank.
March 28 (Mon)
Some analysis of soil samples collected on March 21 and 22 from fivelocations inside of the 1F site, Plutonium-238,-239 and -240 weredetected. (Their density was equivalent to the fallout observed in Japanfollowing an atmospheric nuclear test in the past. However, in view of
the isotope ratio of the detected Plutonium-238 against Plutonium -239
and Plutonium-240, the Plutonium found in two of the five samples may
have come from this accident.)
Nuclide analysis of radioactive materials in the soil will continue to be
carried out.
00：07 Regarding the result of the concentration measurement in water puddles
at unit-2, announced by TEPCO on March 27, TEPCO corrected that as theresult of re-evaluation, judging the measured value of Iodine-134 waswrong, the density of Iodine-134 was actually below the detection limit(while upholding the water surface dose rate of 1,000mSv/h).
17:40 Began transferring puddle water at unit-3 from the condensate storagetank to the surge tank.
20：30 The pump for the fresh water injection to RPV of unit-3 was switched fromthe fire pump trucks to the temporary motor-driven pump.
March 29 (Tue)08：32 Unit-1 injection of freshwater into RPV commenced upon completion of theswitchover from the fire pump truck to the temporary motor-driven
pump.
11：50 Lighting in the central operation room was turned on unit-4.
14：17 Unit-3 injection of freshwater into the spent fuel pool with concrete pumptrucks by TEPCO (approx. 100 t).（~18：18）
16：30 Unit- 2 injection of cooling water into the spent fuel pool, switched to use
freshwater with the temporary motor pumps.
16：36 Ａ puddle of water was found at a centralized environmental facility
process main building. As a result of radioactivity analysis, it identified
radiation. (12 Bq/cm3 in a full dose at a radiation controlled area and 22
Bq/cm3 in a full dose at a non-controlled area.（the adjacent boiler room）)
16：45 Unit -2 water from the condensate reservoirs to a suppression pool water
surge-tanks was initiated to enable water transfer from a condenser tocondensate reservoirs in order to drain water from underground floor of
turbine buildings into a condenser.
March 30 (Wed)I-131 (Radioactive iodine) at the level 3,355 times higher than thestatutory limit stipulated in the Notification of the Nuclear Reactor
Regulation was detected in seawater sampled around the southern water
discharge canal at 13:55 on March 29.
909：45 The temporary motor-driven pump injecting cooling water into the spent
fuel storage pool of unit-2 experienced trouble, the injection pump was
switched to a fire fighting pump truck. However, cracks were found in thehose, suspending the water injection operation. Workers beganaddressing the issues to resume water injection.
14：04 Unit 4 injection of freshwater into the spent fuel storage pool withconcrete pump trucks by TEPCO had been commenced.(Approx. 140 t)(~18:33)
19：05 Unit 2 injection of freshwater into the spent fuel storage pool with the firefighting pump had been resumed .
（Water injection suspended at around 23：50 after the water level in thefire cistern (water source) dropped.)
March 3１ (Ｔｈｕ)
I-131 (Radioactive iodine) at the level about 10,000 times higher than thestatutory limit stipulated in the Notification of the Nuclear Reactor
Regulation was detected in groundwater sampled at unit-1.
( I（iodine）-131 Density：4.3×102Bq/cm3 )08:37 Finished transferring puddle water at unit-3 from the condensate storagetank to the surge tank.
08：51 I-131 (Radioactive iodine) at the level 4,385 times higher than thestatutory reactor density limit was detected in seawater sampled aroundthe southern water discharge canal at 13:55 on March 30.
I-131 (Radioactive iodine) at the level 1,425 times higher than thestatutory limit stipulated in the Notification of the Nuclear Reactor
Regulation was detected in seawater sampled around the northern water
discharge canal on unit-5,-6 at 8:40 on March 30.
09:20 Transferring puddle water from the vertical shaft (trench)of unit-1 to thecentralized environmental facility storage tank had been started(~11：25).
As a result, water level in the trench dropped by 1m (distance from theupper edge increased from 0.14m to 1.14m).
12:00 Draining water from underground floor of turbine buildings at unit-1,
transferring water from a condensate storage tank to a suppression poolwater surge-tank had started.
13：03 Unit-1 injection of freshwater with concrete pump trucks to cool the spent
fuel pool→14:04 Halted dousing (due to problems with the pump battery)→14:29 Restarted dousing (due to operation improvement by battery
replacement)→16:04 Finished dousing the scheduled amount of water (approx. 90 t)
16：30 Unit-3 dousing of freshwater with concrete pump trucks to cool the spent
fuel pool (approx. 105 t).（~19：33）
April 1 (Fri)08:28 Unit-4 Dousing the spent fuel pool by TEPCO (concrete pump trucks)(approx. 180 t) (-14:14)
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11:50 Finished transferring puddle water at unit-2 from the condensate storagetank to the surge tank.
13:40 Began transferring the water accumulated in the basement of unit-6
radwaste building to the unit-5 condenser (hot well)
14:56 Unit-2 Dousing spent fuel pool with freshwater through a normal operationline (approx. 70 t) (-17:05)
15:00 Spread 2,000 liters of anti-scattering agent around the common pool area
on a trial basis (500m2) (-16:04)
15:58 Began transferring water from US military barge #1 to the filtered watertank (halted at 16:25 due to hose problems)April 2 (Sat)09:30 Confirmed that water exceeded 1,000 mSv/h within the pit made forpower cables near the unit-2 intake. Also confirmed cracks approx. 20cm
in length in the concrete lining pit, allowing water within the pit to leak into
the sea through the said cracks (began preparations to halt leakage by
concrete injection) (radioactive nuclides within the pit are currently being
measured and analyzed)
09:52 Unit-3 Dousing spent fuel pool by TEPCO (concrete pump trucks) (approx.
75 t) (-12:54)
10:20 Injected freshwater from US military barge #1 to the filtered water tank(-16:40)
15:26 Finished transferring puddle water at the unit-1 turbine building from thecondensate storage tank to the surge tank.
16:25 Began work to stop leakage from the pit near unit-2 intake by concrete
injection (ended work at 19:15 due to worker dosage exceeding thethreshold value (20 mSv/h))
17:10 Began transferring water from the unit-2 condenser to the condensate
storage tank
April 3 (Sun)12:18 Began the operation of units-1, 2, 3 RPV temporary motor pumps forinjection after switching from power source trucks to the installed powersource13:47 Began work to stop water leakage for leaks within the pit near unit-2
intake, using materials such as polymer absorbers and sawdust (-14:30)
17:14 Unit-4 Dousing spent fuel pool by TEPCO (concrete pump trucks)
17:42 As the sawdust added to the pit near the unit-2 intake to prevent waterleakage began to get dry, sawdust was mixed with water by a mixer truck.
April 4 (Mon)07:08 Added tracer (milky white powder) to pit in order to identify release routeof water leakage for leaks within the pit near the uit-2 intake (-07:11)→ As of 09:30 on April 5, have not confirmed tracer release from intake
11:05 Unit-2 Injection of coolant into the spent fuel pool (-13:37)
17:03 Unit-3 Dousing spent fuel pool from concrete pump truck (approx. 70 t)(-19:19)11

19:03 Releasing low-level radioactive water commenced, pooled in the Central
Radioactive Waste Treatment Facility into sea via south outlet. (total
output: approx. 9,070 tons)（～4/6 06：30, 4/8 14:30 – 4/10 17:40）
21:00 Began releasing low-level radioactive subsurface water in units-5, 6 sub
drain pits into sea via release outlet
April 5 (Tue)
Detected approx. 7.5 million times the concentration limit of iodine (I-131)
from seawater taken around unit-2 bar screen (sampled at 11:50 on April
2)
14:15 Added tracer to gravel under pit to identify release route of water leakage
for leaks within the pit near the unit-2 intake. Confirmed leaking waterfrom cracks contained said tracer.
15:07 Opened holes around pit and injected coagulant (approx. 3,000 liters) as
measure against water leakage for leaks within the pit near the unit-2
intake →leakage amount decreased temporarily, but returned to former
rate. Injected coagulant (6,000 liters total).
17:35 unit-4 Dousing spent fuel pool by TEPCO (concrete pump truck) (approx.
20 t) (-18:22)
April 6 (Wed)Soil samples collected on March 25 and March 28 within the site wereanalyzed and detected Plutonium-238, -239, -240. (Their density was
equivalent to the fallout observed in Japan following an atmosphericnuclear test in the past. However, in view of the activity ratio of thedetected Plutonium-238 against Plutonium-239 and -240, some of thedetected Plutonium may have come from this accident.)
Around 05:38 Confirmed no release of liquid containing radioactive materials
from concrete on sides of the pit near unit-2 intake (Confirmed the waterlevel in unit-2 turbine building was not rising) (more work to stop waterleakage will be continued)
22:30 Activated nitrogen injection equipment for unit-1 primary containment
vessel to prevent hydrogen explosion.
April 7 (Thu)
Water level of the pit was increased by 5cm until noon.
01:31 Injection of nitrogen gas to unit-1 primary containment vessel
commenced.
06:53 Dousing unit-3 by TEPCO (concrete pump truck) (approx. 70 t) (-08:53)
13:29 Dousing unit-2 spent fuel pool with freshwater (approx. 36 t) (-14:34)
18:23 Dousing unit-4 spent fuel pool with freshwater (approx. 38 t) (-19:40)
23:52 No significant abnormalities in units 1～6 nor significant changes in thedata of the monitoring posts in the wake of the earthquake occurred at
23:32
April 8 (Fri)1217:08 Unit-3Dousing spent fuel pool by TEPCO (concrete pump truck) (approx. 75t) (-20:00)
April 9 (Sat)04:10 Unit-1Injection of nitrogen to PCV commenced by high-purity nitrogen gas
generator
13:10 Completed transferring water from unit-2 condenser to the condensate
storage tank
17:07 Unit-4 Dousing spent fuel pool by TEPCO (concrete pump truck) (approx.
90 t) (-19:24)
April 10 (Sun)09:00 Cleaned rubble within site with remote-controlled heavy machinery(-17:00)
09:30 Completed transferring water from unit-1 condenser to the condensate
storage tank
10:37 Unit-2 Injected coolant into spent fuel pool (-12:38)
17:15 Unit-3 Injected coolant (approx. 80 t) into spent fuel pool (-19:15)
April 11 (Mon)10:45 Completed redundant silt fence building for south side breakwater toprevent spread of contaminated water
17:16 External power lost for unit-1 & 2, core injection pump for unit-1-3 shut
down, and unit-1 nitrogen gas injection pump shut down due toearthquake at around 17:16
17:40 Unit-1, 2 Core injection pump shut down due to loss of external power
17:56 Unit-1, 2 External power restored
17:59 Unit-3 Core injection pump shut down
18:04 Unit-1～3 Core injection pump restarted
23:19 Unit-1 Restarted nitrogen gas injection valve opening work
→ 23:24 Nitrogen gas injection valve opened
April 12 (Tue)06:38 Confirmed fire at panel housing batteries within intake sampling building
for unit-1-4 near the south discharge canal on the south side
→ 09:12 Confirmed fire extinguished
10：00 Unit-4 Sampled water from spent fuel pool to grasp condition of fuel in thepool (water temperature: approx. 90ºC; radiation dose: approx. 84mSv/hfrom about 6m above floor of reactor building 5F）
11：20 NISA announced The Rating of the International Nuclear and Radiological
Event Scale (INES) on the events in unit-1～3 was temporarily assessed as
Level 7. (Accident with wider consequences)
16：26 Unit-3 Doused of fresh water (approx. 35 t) with concrete pump trucks tocool spent fuel pool (-17:16)
19：35 Unit-2 Began transferring accumulated water in turbine building from thetrench to the condenser via underwater pump (4/12 19：35～4/13 11：00
temporary shutdown due to leak checks)
April 13 (Wed)1300：30 Unit-4 Doused of freshwater with concrete pump trucks to cool spent fuelpool (-06:57) (approx. 195 t)
08：30 Unit-2 Installed 2 temporary steel water bars (for total of 3 bars) on oceanside of bar screen (- around 10:00)
13：15 Unit-2 Injected water （approx. 60 t） into spent fuel pool (-14:55)
13：50 Units-3, 4 Completed building silt fence in front of screen to prevent
spread of contaminated water
15：02 Unit-2 Restarted transfer of highly radioactive puddle water in trench of
turbine building to condenser
17：04 Unit-2 Halted transfer of highly radioactive puddle water in trench of
turbine building to condenser(actual water transferred: approx. 660 t)
April 14 (Thu)
12：20 Units-1, 2 Completed building silt fence in front of screen and intake
15：56 Unit-3 Dousing spent fuel pool with concrete pump truck (approx. 25 t)(-16:32)
April 15 (Fri)Completed transfer of the temporary diesel generator and pump control
panel for the pump injecting water to the reactor to higher ground as acountermeasures of tsunami
14:15 Unit-2 Completed installation of iron plates on the ocean-side of inlet bar
screen room (4 steel plates out of 7)
14:30 Unit-4 Dousing spent fuel pool with concrete pump trucks (approx. 140 t)(-18:29)
Placed 3 sandbags filled with 100kg zeolite between inlet screen pumprooms of unit-3 and unit-4 (-15:45)
April 16 (Sat)10:13 Unit-2 Injection of freshwater (approx. 45 t) to spent fuel pool via thespent fuel pool cooling line (-11:54)
April 17 (Sun)09:00 Placed a total of 7 zeolite sandbags (-11:15)
・2 zeolite sandbags between inlet screen pump rooms of unit-1, 2・5 zeolite sandbags between inlet screen pump rooms of unit-2, 3
11：30 Surveyed the current situation of the inside of the nuclear reactor buildingof unit-1,3 with remote-controlled robot (-17:30)
14:34 Common spent fuel pool power supply was stopped due to short-circuitingof the end of the power supply circuit. →power supply was restored at
17:30
17:39 Unit-4 Dousing spent fuel pool (approx. 140 t) with concrete pump trucks(-21:22)
April 18 (Mon)09：30 Unit-2 Injected coagulant (liquid glass) into power source trench(approx. 17,000L) (-17:40)
13:28 Units-1 to 3 Confirmed startup condition of injection pump after replacing
the hose used for water injection to the reactors with a new one
14

Shutdown periods for injection pump due to hose replace →Unit-1: 11:50 – 12:12, Unit-2: 12:13 – 12:37, Unit-3: 12:38 – 13:05
14:17 Unit-3 Dousing spent fuel pool (approx. 30 t) (-15:02)
17:40 Completed leak tests for radioactive water transfer line between unit-2
and the central radioactive waste treatment facility
19:00 Completed temporary piping, power source installation, and watertightwork in order to transfer waste liquid to the central radioactive waste
treatment facility
April 19 (Tue)08：00 Unit-2 Injected coagulant (liquid glass) into power source trench(approx. 7,000L) (-15:30)
10:08 Unit-2 Began transferring puddle water (highly radioactive puddle water)in turbine building trenches to central radioactive waste treatment facility
10:17 Unit-4 Dousing spent fuel pool (approx. 40 t) with concrete pump trucks(-11:35)
10:23 Connected transmission cable to external power, proceeded powerreceipt testing, completed linkage line installation work
(connected transmission cables to external power sources between
units-1, 2 and units-3, 4 for power source redundancy)
11:00 Unit-6 Transferred puddle water in turbine building basement (approx.
100m3) to condenser (-15:00)
16:08 Unit-2 Injection of water (approx. 47 t) into spent fuel pool (-17:28)
April 20 (Wed)9:51 Unit-6 Temporarily stopped the pump of residual heat removal system(RHR) in order to change position of temporary hoses for residual heatremoval seawater (RHRS) system→After carrying out the work of transferring of the pump for temporary
Residual Heat Removal (RHR) , cooling was resumed (15:56)
17:08 Unit-4 Dousing spent fuel pool (approx. 100 t) with concrete pump trucks(-20:31).
April 21 (Thu)・ Completed seal reinforcement work on leak areas using grout
・ Estimated that the amount of highly radioactive contaminated waterleaked from cracks in the concrete near the unit-2 intake screen
confirmed on April 2 was approx. 520m3, with dosage of approx. 4.7 x1015 Bq
17:14 Unit-4 Dousing spent fuel pool (approx. 140 t) with concrete pump trucks(-21:20)
April 22 (Fri)
13:40 Unit-3 Injection of water (approx. 10 t) into spent fuel pool (-14:00)
14:19 Unit-3 Dousing spent fuel pool (approx. 50 t) with concrete pump trucks(-15:40)
15:55 Unit-2 Injection of water (approx. 50 t) into spent fuel pool (-17:40)
15

17:52 Unit-4 Dousing spent fuel pool (approx. 200 t) with concrete pump trucks(-23:53)→ Temperature of spent fuel pool water (approx. 91ºC before dousing)
April 23 (Sat)
12:30 Unit-4 Dousing spent fuel pool (approx. 140 t) with concrete pump trucks(-16:44)→Temperature of spent fuel pool water (approx. 83ºC → approx. ６６ºC)
April 24 (Sun)12:25 Unit-4 Dousing spent fuel pool (approx. 165 t) with concrete pump trucks(-17:07) → Temperature of spent fuel pool water (approx. 86ºC → approx.
81ºC)
April 25 (Mon)
10:12 Unit-2 Injection of fresh water into spent fuel pool via the spent fuel poolcooling (FPC) system (approx. 38 t) (-11:18)
10:57 Units-1～3 Due to enhancement work of external power supply, the power
supplies to the motor-driven pumps injecting fresh water to the Reactor
Pressure Vessel was switched from external power supplies to temporary
diesel generators.
18:15 Unit-4 Dousing spent fuel pool (approx. 210 t) with concrete pump trucks
to cool spent fuel pool (-24:26)
April 26 (Tue)
12:22 Unit-5 Temporary stopped the pump of residual heat removal system(RHR) due to enhancement work of external power supply (-16:43)
12:25 Unit-3 Injection of fresh water (approx. 47.5 t) into spent fuel pool(-14:03)
13:30 Unit-3 Began full-scale distribution of anti-scattering agent (5,000m2) on
ocean side of turbine building (-17:00)
16:50 Unit-4 Dousing of spent fuel pool (approx. 130 t) with concrete pumptrucks to cool spent fuel pool (-20:35)
April 27 (Wed)10:02 Unit-1 Began operation to incrementally increase reactor injection ratio
from approx. 6m3/h to a maximum of approx. 14m3/h
12:18 Unit-4 Began dousing with concrete pump trucks (approx. 85 t) to cool
spent fuel pool (-14:01 halted, 14:32 restarted – 15:15 finished)
April 28 (Thu)
10:15 Unit-2 Injected fresh water into spent fuel pool (approx. 43 t) (-11:28)
11:55 Unit-4 Sampling of pool water (-12:07)
April 29 (Fri)
10:14 Unit-1 Changed reactor water injection ratio from 10m3/h to 6m3/h
11:36 Unit-1 Inspected conditions at reactor building 1F with remote controlled
robot to confirm whether significant water leakage was present inprimary containment vessel (-14:05)
April 30 (Sat)12:08 Units-3, 4 Completed external power increase work (power received from16

Ookuma line 3L).
Around 14:05 Unit-2 Restarted transfer of water from turbine building trench pit
to collective waste processing facility
May 1 (Sun)13:35 Unit-2 Began trench pit closing work
14:00 Unit-6 Transferred puddle water in the basement of turbine building(approx. 120m3) to temporary tanks(-17:00)
May 2 (Mon)
10:00 Unit-6 Transferred puddle water in the basement of turbine building(approx. 220m3) to temporary tanks (-16:00)
10:05 Unit-2 Injected fresh water into spent nuclear fuel pool (approx. 55t)(-11:40)
12:58 Units-1～3 Installed alarm onto core injection pump (-14:53)
15:03 Units-5, 6 Trial power supply work on startup transformer (5SB) as part ofpermanent power supply restoration work (-15:03)
May 3 (Tue)14:00 Unit-6 Transferred puddle water in the basement of turbine building(approx. 114m3) to temporary tanks
May 4 (Wed)09:40 Unit-2 Performed concrete casting as part of trench sealing work (80m3)(-15:45)
10:09 Unit-3 Changed reactor injection ratio from approx. 7m3/h to 9m3/h inconjunction with reactor pressure vessel temperature increase
May 5 (Thu)
12:19 Unit-4 Began dousing of spent fuel pool with concrete pump trucks(-20:46)
16:36 Unit-1 Began ventilation of reactor building via full operation of local
exhaust fans (6 units) in order to improve reactor building working
environment
May 6 (Fri)
02:04 Earthquake occurs – epicenter at Hamadori, Fukushima (max. JMA seismic
intensity 5-lower). No abnormalities at 1F, 2F.
09:36 Unit-2 Injection of water into spent fuel pool with temporary motorizedpump (-11:16)
10:01 Unit-1 The ratio of water injection for submersion of reactor containment
vessel was increased from approx. 6m3/h to approx. 8m3/h
12:38 Unit-4 Dousing spent fuel pool (180t) with concrete pump trucks (-17:51)
14:00 Unit-6 Transfer of puddle water in the basement of turbine building(120m3) to temporary tanks was resumed (-17:00)
May 7 (Sat)09:22 Unit-3 Temporarily halted transfer of radioactive waste liquid from unit-2
turbine building to the central radioactive waste treatment facility forreactor injection piping work (transfer restarted at 16:02)
10:00 Unit-6 Began transfer of puddle water from turbine building to temporary
17

tank (-15:00)
14:05 Unit-4 Began dousing (approx. 120t) with concrete pump trucks (-17:30)
May 8 (Sun)12:10 Unit-3 Injected water into spent fuel pool using temporary motorizedpump（approx. 60t） (-14:10)
16:18 Unit-3 Began draining water from condenser into ground in the basementof turbine building
20:08 Unit-1 Disconnected ducts penetrating the double-entry doors into thereactor building and partially opened them
May 9 (Mon)04:01 Unit-1 Performed sampling, retrieved exhaust ducts (-04:17)
04:17 Unit-1 Opened the double-entry doors of the reactor building
04:18 Unit-1 Began entry of workers into reactor building for reactor building
internal environment survey
All workers left after first survey was completed. Max. exposure dose ofentered workers:10.5mSv (-04:47)
05:00 Unit-1 Measured atmospheric dose rate after opening double-entry doorsof the reactor building; no effect on nearby areas
12:14 Unit-3 Injected fresh water into spent fuel pool (12:39 – 14:36, （approx.
80t）also injected corrosion inhibitor (hydrazine, approx. 0.5m３)) (-15:00)
14:00 Unit-6 Transfer of puddle water in the basement of turbine building totemporary tanks was resumed
16:05 Unit-4 Dousing spent fuel pool using water (16:11 – 18:38, (approx. 100t)
also injected hydrazine (approx. 0.23m3)) with concrete pump trucks(-19:05)
May 10 (Tue)09:01 Unit-2 Temporarily halted transfer of high level radioactive waste liquidfrom turbine building trench to collective treatment facility (due to unit-3
reactor water injection line replacement work)
09:31 Unit-3 Began installing transfer line on turbine building side
10:00 Unit-6 Restarted transfer of puddle water in the basement of turbine
building to temporary tanks(-16:00)
11:00 Unit-6 Transferred puddle water in the basement of reactor building(approx. 10m3) to Unit-6 radwaste processing building (-12:30)
13:09 Unit-2 Injected fresh water into spent fuel pool (13:19 – 14:35, (approx.
56t) also injected corrosion inhibitor (hydrazine, approx. 1.2m3))(-14:45)
May 11 (Wed)
Unit-3: Welded sealing plug onto feedwater line
08:47 Units-1 - 3 Due to partial power supply shutdown caused by restoration of
the Okuma Power Line 2, reactor injection pump power source wasswitched to temporary diesel generator for reactor injection pump
operation18

08:50 Unit-1 Shut down reactor containment vessel nitrogen gas supply
equipment due to partial power supply shutdown caused by restoration of
the Okuma Power Line 2
10:00 Unit-6 Restarted transfer of puddle water from turbine building totemporary tank (approx. 120m3) (-16:00)
11:00 Unit-6 Transferred puddle water in the basement of turbine building tounit-6 waste processing building (approx. 10m3) (-13:30)
12:30 Unit-3 Discovered water leakage into cable pit near screen equipment
Since the water level within the pit did not increase, both confirming
source of leakage into the pit and nuclides analyzing are taken in action.
15:55 Units-1 - 3 Due to completion of Okuma Power Line 2 restoration (15:20),
switched reactor injection pump power source from temporary diesel
generator to system power source
15:58 Unit-1 Restored reactor containment vessel nitrogen gas supply
equipment
16:07 Unit-4 Dousing spent fuel pool (16:14 – 19:36 (approx. 120t) hydrazine
injected) (-19:38)
18:45 Unit-3 Confirmed leak stoppage for water leak into pit on south screen
room via measures such as concrete injection until 18:40
May 12 (Thu)
05:00 Unit-1 Confirmed reactor water level for fuel boundary A is beneath thescale
10:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tanks (approx. 120m3) (-16:00)
10:30 Unit-6 Transferred puddle water in the basement of reactor building tounit-6 radwaste processing building (approx. 7.5m3)(-13:30)
12:20 Completed station power source switching due to Okuma Power Line 3
restoration
15:20 Unit-2 Restarted transfer of high level radioactive waste liquid from turbine
building trench to collective waste processing facility
16:53 Unit-3 Began injection of water into reactor pressure vessel fromfeedwater system at rate of 3m3/h (injection of water from fire
extinguishing system remains unchanged)
May 13 (Fri)10:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tanks (approx. 100m3) (-15:00)
11:30 Unit-6 Transferred puddle water in the basement of reactor building tounit-6 radwaste processing building (approx. 3.3m3) (-13:15)
16:04 Unit-4 Dousing spent fuel pool (16:20 – 18:41 injected 0.12m3 ofhydrazine) (approx. 100 tons) (-19:04)
May 14 (Sat)10:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tanks (approx. 100m3) (-15:00)
13:00 Unit-2 Injected water into spent fuel pool (approx. 56 t) (-14:37)
19

May 15 (Sun)10:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tanks (approx. 100m3) (-15:00)
13:28 Unit-1 Increased reactor injection ratio from 8m3/h to 10m3/h in order tomonitor trends of parameters for reactor pressure vessel and reactor
containment vessel after reactor injection ratio increase
14:33 Unit-3 Injected 5 sodium borate into reactor via fire extinguishing line
(approx. 180kg) (-17:00)
16:25 Unit-4 Dousing spent fuel pool (16:26 – 18:30 injected 0.30m3 ofhydrazine) (approx. 140 t) (-20:25)
May 16 (Mon)
10:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tanks (approx. 80m3) (-14:00)
15:00 Unit-3 Injected fresh water into spent fuel pool via FPC system line (approx.
106 t) (15:10 - 17:30 hydrazine injection approx. 0.88m3) (-18:32)
May 17 (Tue)10:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tanks (approx. 80m3) (-17:00)
10:11 Unit-3 Increased reactor injection ratio (feedwater system: 6 → 9m3/h,
extinguisher system remains at 9m3/h, total: 18m3/h)
11:50 Unit-1 Changed reactor injection ratio from approx. 10m3/h to approx.
6m3/h
16:14 Unit-4 Dousing spent fuel pool with freshwater (approx. 120 t) (16:40 –18:35 hydrazine injection approx. 0.6m3) (-20:06)
18:04 Unit-3 Began transferring puddle water in the basement of turbine building
to collective waste processing facility
May 18 (Wed)09:24 Unit-2 Entered reactor building to measure dosage
10:00 Unit-6 Transferred puddle water in the basement of turbine building(approx. 80m3) to temporary tanks (-14:00)
10:30 Unit-6 Transferred puddle water in the basement of reactor building(approx. 10.5m3) to unit-6 waste processing building (-12:30)
13:10 Unit-2 Injected fresh water to spent fuel pool via FPC system line(approx.
53 t) (13:15 – 14:30 hydrazine approx. 1.1m3) (-14:40)
16:30 Unit-3 Conducted pre-inspection of reactor building to confirm current
state of nitrogen sealing work area (-16:40)
May 19 (Thu)
16:30 Unit-4 Dousing spent fuel pool with fresh water (approx. 100 t) (-19:30)
May 20 (Fri)
09:30 Unit-1 Entered reactor building to monitor water level and measure dosage(-12:15)
14:15 Unit-3 Increased reactor injection ratio via feedwater system from 9 to
12m3/h15:06 Unit-1 Dousing spent fuel pool with fresh water (approx. 50 t) (-16:15)
20

17:39 Unit-3 Changed reactor injection ratio via extinguishing system from 9 to
6m3/h
May 21 (Sat)
14:00 Unit-6 Transferred puddle water in the basement of turbine building(approx. 80m3) to temporary tank (-18:00)
16:00 Unit-4 Dousing with fresh water (approx. 130 t) (16:23 – 19:00 hydrazine
approx. 0.4m3) (-19:56)
May 22 (Sun)13:02 Unit-2 Injection of fresh water (approx. 56 t) from fuel pool coolingcleanup system to spent fuel pool (13:04 – 14:03 hydrazine approx.
1.0m3) (-14:40)
15:33 Unit-1 Dousing spent fuel pool with fresh water (approx. 90 t) (-17:09)
May 23 (Mon.)
11:31 Unit-3 Changed reactor injection ratio via extinguishing system from 6 to
5m3/h
14:08 Unit-3 Changed reactor injection ratio via extinguishing system from 5 to
4m3/h
16:00 Unit-4 Dousing spent fuel pool with fresh water (approx. 100 t) (16:08 –18:30 hydrazine approx. 0.3m3) (-19:09)
May 24 (Tue)09:00 Unit-6 Transferred puddle water in the basement of turbine building(approx. 400m3) to temporary tank (-19:00)
10:15 Unit-3 Injected fresh water (approx. 100 t) into spent fuel pool via FPC
system line (10:20 – 12:56 hydrazine approx. 0.8m3) (-13:35)
May 25 (Wed)09:00 Unit-6 Transferred puddle water in the basement of turbine building(approx. 336m3)
to temporary tank (-19:00)
09:05 Unit-2 Temporarily halted transfer of highly radioactive puddle water fromturbine building trench to collective waste processing facility due to powersource switching (-15:30)
09:14 Unit-1 Temporarily halted nitrogen sealing of reactor containment vessel
due to power source switching (09:14 - 9:18, 15:16 - 15:18)
15:45 Unit-1 Confirmed shutdown of nitrogen supply compressor. Began sealing
upon switching to reserve unit (19:44)
16:36 Unit-4 Injection of spent fuel pool with fresh water (approx. 121 t) (16:42– 18:49 hydrazine approx. 0.3m3) (- 13:35)
May 26 (Thu)
10:06 Unit-2 Injected fresh water (approx. 53 t) into spent fuel pool via FPC
system line (10:10 – 11:10 hydrazine injection) (-11:36)
14:45 Unit-2 Transferred condenser water to turbine building due to reactor
pressure vessel water injection piping work (-5/27 14:30)
May 27 (Fri)
09:00 Unit-6 Transferred puddle water in the basement of turbine building(approx. 336.6m3) to temporary tank (-19:00)
21

10:30 Unit-1 Attached water level meter for puddle water in reactor building,sampled underground puddle water, and installed hose for spent fuel pool
17:05 Unit-4 Dousing with fresh water (approx. 100 t) (-20:00)
May 28 (Sat)09:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tank (-19:00)
10:20 Unit-6 Transferred puddle water in the basement of reactor building(approx. 12m3) to Unit-6 waste processing building (-12:10)
13:28 Unit-3 Injected fresh water (approx. 50 t) into spent fuel pool via FPC
system line (-15:08)
16:47 Unit-1 Conducted leak test in order to inject fresh water into spent fuelpool via FPC system line to spent fuel pool (-17:00)
17:56 Unit-4 Dousing with fresh water (approx. 60 t) (-19:45)
20:54 Unit-3 Halted injection of water from extinguishing system piping into
reactor (injection of water from feedwater system into core (approx.
13.5m3/h))
21:14 Unit-5 Confirmed shutdown of residual heat removal seawater (RHRS)
system pump. Began switch to reserve pump (5/29 8:12); RHRS pumpstarted up (5/29 12:31); Cooling of core with residual heat removal (RHR)
system had been resumed (5/29 12:49)
May 29 (Sun)09:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tank (-19:00)
11:10 Unit-1 Injection of fresh water (approx. 168 t) into spent fuel pool from
FPC system (-15:35)
11:33 Unit-2 Began injection of water into core from feedwater system (approx.
5m3/h) in addition to injection of water into core from extinguishingsystem (7m3/h)
May 30 (Mon)
10:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tank (-17:30)
11:15 Unit-2 Leak testing of spent fuel pool alternative cooling equipment
secondary system. Began trial operation of said system (May 30, 15:02).
12:06 Unit-2 Injection of fresh water (approx. 53 t) into spent fuel pool from FPC
system (-13:52)
18:05 Unit-2 Halted injection of water into reactor from extinguishing systempiping (continued injection of approx. 5m3/h from feedwater system)
May 31 (Tue)Around 08:00 Confirmed oil leakage into sea near curtain wall of units-5, 6 intake
at dedicated port .Installed absorption mat and oil fence near seawall(Around 14:00 and at 16:50)
Around 09:00 Unit-3 Preliminary survey of reactor building by remote controlled
robot ( - Around 16:00)
22

11:40 Unit-2 Leak testing of spent fuel pool alternative cooling equipment
primary system, began full operation of said unit (May 31, 17:21)
Around 14:30 Unit-4 Confirmed loud noise while wireless controlled unmanned
heavy machinery was cleaning debris outside the south side of the reactor
building. Later confirmed that said noise was caused by rupture of oxygentank buried in the rubble.
20:30 Unit-1 Changed reactor injection ratio from approx. 6m3/h to approx.
5m3/h
June 1 (Wed)
10:10 Unit-3 Changed reactor injection ratio from approx. 13.5m3/h to approx.
12.5m3/h (May 31 10:19), then from approx. 12.5m3/h to approx.
11.5m3/h
14:00 Unit-6 Began transfer of puddle water in the basement of turbine building
to temporary tank
14:34 Unit-3 Injection of fresh water (approx. 40 t) into spent fuel pool from FPC
system (14:41 – 15:26 also injected approx. 0.14m3 of hydrazine)(-15:54)
June 2 (Thu)
12:50 Unit-3 Transferred condenser water to condensate storage tank in
preparation for transfer of puddle water in the basement of turbine building
to condenser (-June 4, 21:56)
14:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tank ( - June 8, 18:00) (temporarily halted on June 5 from14:00 – 14:45)
June 3 (Fri)
13:16 Unit-3 Temporarily halted coolant injection due to core injection supply line
route change work (-13:32)
13:49 Unit-2 Temporarily halted coolant injection due to core injection supply line
route change work (-14:09)
14:35 Unit-4 Dousing spent fuel pool with fresh water (approx. 210 t) (-21:15)
Around 15:00 Unit-1 Confirmed state of reactor building using remote-controlled
robot ( - Around 17:00)
18:39 Unit-2 Transferred highly radioactive puddle water from turbine building
trench to condenser hot well inside turbine building ( - June 4, 12:28)
June 4 (Sat)09:57 Unit-1 Temporarily halted coolant injection due to core injection supply line
route change work (-13:56)
10:02 Unit-1 Injection of water into core from extinguishing pump (-13:43)
14:23 Unit-4 Dousing spent fuel pool with fresh water (approx. 180 t) (-19:45)
18:39 Unit-2 Transferred highly radioactive puddle water within turbine building
trench to collective waste processing facility (process main building) (June 16, 8:40)
June 5 (Sun)23

10:16 Unit-1 Injection of fresh water into spent fuel pool from FPC system(approx. 15 t) (-10:48)
13:08 Unit-3 Injection of fresh water (approx. 60 t) into spent fuel pool from FPC
system (-15:14)
18:26 Unit-3 Transferred puddle water within turbine building to condenser(-June 9, 10:44)
June 6 (Mon)15:56 Unit-4 Dousing spent fuel pool with fresh water (approx. 90 t) (-18:35)
June 8 (Wed)
10:05 Unit-6 Transferred puddle water in the basement of reactor building(approx. 17m3) to Unit-6 waste processing building (-12:40)
17:54 Unit-1 Temporarily halted nitrogen provision due to confirmation ofincrease in nitrogen provision equipment pressure (14:57); restarted
nitrogen provision due to restoration of power source for said equipment
16:12 Unit-4 Dousing spent fuel pool with fresh water (approx. 102 t) (-19:14)
June 9 (Thu)
09:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tank (-18:00)
Around 10:30 Units-2, 3 Conducted trial water sending of recirculating seawater
purification unit installed in screen area ( - around 15:00)
13:42 Unit-3 Injected fresh water (approx. 55 t) from FPC system to spent fuelpool (-19:14)
June 10 (Fri)
Conducted closing work in 39 locations as part of puddle water leakage
prevention measures for the screen pit of each Unit
June 11 (Sat)10:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tank (-15:00)
11:45 Unit-2 Conducted trial operation of reactor building local exhaust fans(-12:19), opened double doors (12:39), began full scale operation (12:42)
15:30 Unit-3 Transferred puddle water in the basement of turbine building tocollective waste processing facility (-June 12, 17:01)
June 12 (Sun)10:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tank (-15:00)
10:09 Unit-3 Injected fresh water from FPC system into spent fuel pool (-11:48)
June 13 (Mon)
10:00 Units-2, 3 Began full scale operation of recirculating seawater purification
unit installed in screen area
10:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tank (-16:00)
14:58 Unit-2 Transferred Unit-1 condenser water (approx. 75 t) to Unit-1 turbine
building basement in preparation for transfer of turbine building puddle
water to Unit-1 condenser(-17:43)
24

16:36 Unit-4 Dousing spent fuel pool with fresh water (approx. 150 t) (-21:00)
June 14 (Tue)03:45 Performed trial operation of puddle water processing system cesium
absorption unit using low-level contaminated water (-14:00)
10:00 Unit-6 Transferred puddle water in the basement of turbine building totemporary tank (-16:00)
10:05 Unit-3 Transferred puddle water in turbine building to collective waste
processing facility (-June 16, 8:46)
16:10 Unit-4 Dousing spent fuel pool with fresh water (approx. 150 t) (-20:52)
June 15 (Wed)10:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:00)
10:06 Unit-1 Changed reactor injection ratio from approx. 5m3/h to approx.
4.5m3/h (-20:52)
10:33 Unit-1 Transferred condenser water to condensate storage tank (-June 16,
9:52)
11:55 Unit-6 Transferred puddle water in basement of reactor building to unit-6
waste processing building (-14:00)
13:10 Trial operation of decontamination unit in the water treatment facility was
conducted (-around 20:35)
Around 22:40 Combined operation of cesium adsorption unit anddecontamination unit was conducted (-June 16, around 00:20)
June 16 (Thu)
Around 00:20 Began combined continuous operation of cesium adsorption unit
and decontamination unit
10:00 Unit-6 Began transferring puddle water in basement of turbine building totemporary tank
13:14 Unit-4 Injected fresh water (approx. 75 t) into spent fuel pool (-15:44)
Around 19:20 Temporarily halted continuous operation of water treatment facility
due to cesium adsorption unit leakage
June 17 (Fri)10:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:00)
10:19 Unit-3 Injected fresh water (approx. 49 t) into spent fuel pool from FPC
system (-11:57)
14:20 Unit-2 Began transferring highly radioactive puddle water in turbine
building trench to turbine building condenser hot well; temporarily haltedtransfer due to transfer pump malfunction (14:59)
20:00 Began full-scale operation of water treatment facility
June 18 (Sat)00:54 Temporarily halted operation of water treatment facility due to cesium
adsorption unit filter surface dose rate reaching exchange standard levels
10:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:00)
25

10:00 Temporarily halted operation of recirculating seawater purification unit for
maintenance (-June 20, around 10:00)
13:31 Unit-3 Transferred puddle water in basement of turbine building tocollective waste processing facility (-June 20, 00:02)
16:05 Unit-4 Injected fresh water (approx. 99 t) into spent fuel pool (-19:23)
Around 21:00 Confirmed water leakage during exchange preparation work forwater treatment facility adsorption tower
June 19 (Sun)09:14 Unit-4 Filled device storage pool (DSP) with water (approx. 80 t) (-11:57)
10:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:00)
Conducted the following tasks in preparation for halted of Okuma PowerLine 2 due to repairs on gateway building between Units-1, 2:● Unit-1 Temporarily switched core injection pump power source to an
emergency diesel generator (10:35 – 15:47), temporarily halted
nitrogen sealing (11:48 – 16:05)● Unit-2 Temporarily switched core injection pump power source to an
emergency diesel generator (10:49 – 15:35), temporarily halted spent
fuel pool alternative cooling unit(11:03 – 16:00), temporarily halted
local exhaust fan (12:12 – 16:22)● Unit-3 Temporarily switched core injection pump power source to D/G(11:03 – 15:22), temporarily halted temporary Units-1/2 M/C (A), (B)and power center 2C (13:09 – 15:09) – received power from Okuma
Power Line 3 in the meantime
19:30 Conducted trial water sending using highly radioactive contaminated waterof cesium adsorption unit (-23:45)
20:46 Unit-2 Entered reactor building
20:51 Unit-2 Slightly opened one door and fully opened the other of reactor
building double doors (June 20, 05:00)
June 20 (Mon)09:49 Unit-4 Filled device storage pool (DSP) with water (-09:52) (10:06 - June
21, 11:29)
10:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:00)
10:25 Conducted trial water sending using highly radioactive contaminated waterof cesium adsorption unit (-14:50)
13:37 Unit-2 Transferred puddle water in turbine building trench to Unit-1
condenser (-June 21, 17:09)
14:30 Unit-2 Opened external doors of reactor building large freight entrance
June 21 (Tue)00:45 Began trial operation of water treatment facility
07:20 Halted trial operation of water treatment facility due to shutdown of
coagulation equipment solution injection unit26

10:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:00)
10:02 Unit-1 Changed reactor injection ratio from approx. 4.5m3/h to approx.
4.0m3/h
10:04 Unit-2 Changed reactor injection ratio from approx. 5.0 m3/h to approx.
4.5m3/h
10:06 Unit-3 Changed reactor injection ratio from approx. 11.0 m3/h to approx.
10.0m3/h
11:05 Unit-6 Transferred puddle water in basement of reactor building to Unit-6
waste processing building (-13:30)
11:45 Unit-4 Filled device storage pool (DSP) with water (-12:52)
11:55 Unit-1 Temporarily halted nitrogen sealing due to temporary transformer
installation work (-18:03)
13:15 Unit-2 Entered reactor building, performed measurement device
calibration and pre-inspection of nitrogen sealing locations
15:32 Unit-3 Transferred puddle water in basement of turbine building tocollective waste processing facility (-June 27, 15:44)
June 22 (Wed)08:32 Unit-4 Filled device storage pool (DSP) with water (-14:31)
09:56 Unit-2 Began transferring puddle water in turbine building trench tocollective waste processing facility
10:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:00)
10:02 Unit-1 Changed reactor injection ratio from approx. 4.0m3h to approx.
3.5m3/h
10:04 Unit-2 Changed reactor injection ratio from approx. 4.5m3h to approx.
4.0m3/h
10:20 Halted operation of water treatment facility due to flushing work (- June 23,
00:13)
14:31 Unit-4 Injected freshwater into spent fuel pool (-16:38)
June 23 (Thu)
00:43 Began trial operation of water treatment facility
09:32 Unit-4 Filled device storage pool (DSP) with water (-15:29)
10:13 Unit-3 Changed reactor injection ratio from approx. 10.0 m3/h to approx.
9.5m3/h
10:36 Unit-2 Performed temporary reactor pressure gauge installation (-12:26)
13:00 Temporarily halted trial operation of water treatment facility due toexchange cesium adsorption tower (-14:44)
18:27 Units-1, 2 Began injection of fresh water into reactor for Units-1, 2 using
Unit-1 reactor injection pump
June 24 (Fri)
Unit-2 Halted basement puddle water level meter installation work using
robots27

Around 06:58 Unit-2 Unmanned helicopter which was collecting dust rising fromreactor building opening performed forced landing onto reactor buildingroof
10:00 Temporarily halted trial operation to exchange water treatment facility
cesium adsorption tower (-12:50)
10:07 Unit-3 Changed reactor injection ratio from approx. 9.5m3/h to approx. 9.0
m3/h
10:30 Unit-3 Performed dosage survey using robot for reactor building (-12:42)
Around 12:50 Began processing using fresh water processing unit
16:35 Unit-5 Began cooling of spent fuel pool using FPC system
June 25 (Sat)10:00 Temporarily halted recirculating seawater purification unit due tomaintenance
10:00 Temporarily halted trial operation of water treatment facility due toexchange cesium adsorption tower (-15:00)
15:24 Automatic shutdown of water treatment facility due to oil separator waterlevel low alarm
16:10 Automatic shutdown of water treatment facility due to oil separator waterlevel low alarm
16:35 Restarted trial operation of water treatment facility
June 26 (Sun)09:56 Unit-3 Injected boron water (approx. 45 t) from FPC system to spent fuelpool
10:00 Temporarily halted trial operation of water treatment facility due toexchange cesium adsorption tower vessel (-18:10)
16:20 Units-1 through 3 Began using water processed at water processing
system alongside injection from filtered water tank for injection into
reactorJune 27 (Mon)
Performed the following work due to station power source switch in linewith Okuma power line 2 restoration:● 08:23 Unit-2 Temporarily shut down spent fuel pool alternative coolingequipment (-16:53)● 08:51 Unit-1 Temporarily shut down nitrogen sealing equipment (-15:07)● 09:02 Unit-2 Shut down turbine building trench puddle water transfer
pump to the collective waste processing facility (-17:07)
15:00 Unit-3 Injected boron (approx. 60 t) into spent fuel pool from FPC system(-17:18)
17:00 Unit-3 Transferred puddle water in basement of turbine building tocollective waste processing facility (two pumps) (-June 28, 9:58)
17:55 Halted supply of processed water of water treatment facility due todiscovery of leakage from piping
18:03 Unit-5 Began operation of emergency diesel generator 5A, restoring it to
standby condition28June 28 (Tue)
09:40 Unit-4 Filled device storage pool (DSP) with water (-15:29)
11:00 Unit-6 Transferred puddle water in basement of reactor building to Unit-6
waste processing building (-13:20)
Around 12:00 Unit-6 Transferred puddle water in turbine building basement,
confirmed that low level radioactive contaminated water was leaking fromthe temporary tank in which puddle water was being stored
12:32 Unit-5 Began operation of emergency diesel generator 5B, restoring it to
standby condition
15:55 Units-1 ～3 Restarted supply of processed water for reactor injection fromwater treatment facility
20:06 Unit-2 Confirmed start of nitrogen sealing for reactor containment vessel inorder to reduce risks of hydrogen combustion in the reactor containment
vesselJune 29 (Wed)
10:59 Units-1 ～ 3 Temporarily halted recirculated water injection cooling forreactor (-13:33)
13:28 Unit-4 Entered 5th floor of reactor building, performed inspection prior tospent fuel pool alternative cooling work (-14:21)
14:45 Unit-3 Injected fresh water (approx. 30 t) from FPC system to spent fuelpool (-15:53)
June 30 (Thu)
08:56 Unit-3 Transferred puddle water in basement of turbine building tocollective waste processing facility (1 pump)
09:00 Shut down water treatment facility fresh water processing unit due toconcentration tank increase / connection work
10:02 Unit-5 Temporarily stopped residual heat removal system (RHR) pump toswitch power sources of surrounding equipment (-11:48)
10:43 Unit-3 Conducted leak testing of primary alternative spent fuel pool coolingsystem10:46 Temporarily halted water treatment facility operation for adsorption tower
vessel exchange (-13:35)
11:30 Unit-4 Injected fresh water into spent fuel pool via temporary dousing
equipment (-11:55)
13:00 Unit-6 Transferred puddle water collected in the temporary tank, which
had been sent from the basement of the turbine building, to the mega float(-19:00)
14:36 Automatic shutdown of water treatment facility due to low alarm activationof water processing tank water level
18:33 Unit-3 Began trial operation of alternative spent fuel pool cooling system
18:50 Restarted operation of water treatment facility
July 1 (Fri)29

07:27 Units-1 ～ 3 Temporarily halted feedwater from processed water due tobuffer tank installation / connection work (-July 2, 14:22, actual injection
18:00-)
10:00 Unit-6 Began transferring puddle water in basement of turbine building totemporary tank
10:00 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to the mega float (-July
3, 16:00)
July 2 (Sat)10:30 Temporarily halted water treatment facility operation due to adsorption
tower vessel exchange (-13:45)
July 3 (Sun)10:00 Unit-5 Temporarily shut down temporarily installed residual heat removal
seawater system (RHRS) pump due to outlet side piping exchange work forsaid pump (-13:36)
10:15 Unit-5 Temporarily shut down residual heat removal (RHR) system pump(-13:40)
10:20 Unit-5 Temporarily shut down temporary RHRS pump (B) (-13:22)
10:39 Temporarily halted water treatment facility operation due to adsorption
tower vessel exchange (-12:50)
16:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank
20:17 Halted transfer of puddle water to water treatment facility buffer tank due
to buffer tank being full; however, contaminated water processing andcore injection continued to be carried out
July 4 (Mon)08:50 Unit-1 Temporarily increased flow rate to 7.5m3/h to perform flushing due
to reactor injection ratio dropping to 3.0m3/h (8:40- 8:50); adjusted flowrate to 3.8m3/h afterwards
09:13 Unit-4 Filled device storage pool (DSP) with water (-18:18)
10:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:00)
13:30 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to the mega float(-17:00)
17:18 Restarted transfer of processed water to buffer tank
July 5 (Tue)10:00 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to the mega float(-17:00)
10:30 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:30)
10:30 Temporarily halted water treatment facility operation due to adsorption
tower vessel exchange (-13:20)
30

15:10 Unit-1 Injected fresh water (approx. 75 t) from FPC system to spent fuelpool (-17:30)
July 6 (Wed)06:53 Halted transfer of processed water to buffer tank due to buffer tank waterlevel reaching upper control value. However, processing of contaminatedwater and injection into core continued to be carried out.
08:00 Temporarily shut down fresh water processing unit (-July 7, 11:09)
08:45 Unit-6 Transferred puddle water in basement of turbine building to unit-6
waste processing building (-10:50)
10:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-17:00)
10:20 Unit-4 Carried out preparations for spent fuel pool alternative cooling work(-10:33)
July 7 (Thu)
04:52 Began transfer of processed water to buffer tank due to buffer tank waterlevel reaching lower control value
10:09 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to the mega float(-17:00)
10:30 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:30)
11:00 Temporarily halted water treatment facility operation due to adsorption
tower vessel exchange (-July 8, 02:45)
15:00 Unit-2 Halted transfer of puddle water from turbine building trench due towater level in collective waste processing facility reaching transfer
stopping levels
23:30 Temporarily shut down puddle water transfer pump due to drop inprocessed water temporary tank water level (-July 8, 02:45)
July 8 (Fri)
02:45 Restarted transfer of processed water to buffer tank
04:44 Temporarily shut down puddle water transfer pump due to drop inprocessed water temporary tank water level
08:20 Unit-4 Temporarily shut down unit-3 alternative spent fuel pool coolingsystem due to alternative spent fuel pool cooling system work (-14:24)
08:22 Unit-4 Filled device storage pool (DSP) with water (-13:52)
10:00 Unit-4 Performed piping robustness confirmation as part of alternative
spent fuel pool cooling system work (-11:30)
10:00 Temporarily shut down water treatment facility operation due toadsorption tower vessel exchange (-12:04)
10:00 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to the mega float(-17:00)
10:30 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:30)
31

10:44 Unit-2 Performed flushing for transfer line between turbine building trenchand collective waste processing facility (-12:30)
13:51 Restarted sending of processed water to buffer tank due to buffer tankwater level nearing lower control values
July 9 (Sat)07:35 Halted transfer of processed water to buffer tank due to drop in processedwater temporary tank water levels; however, contaminated water
processing and core injection continued to be carried out
10:00 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to mega float (-17:00)
10:30 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:30)
14:49 Unit-3 Halted transfer of puddle water in basement of turbine building tocollective waste processing facility
15:22 Unit-3 Began flushing of transfer line which transferred puddle water frombasement of turbine building to collective waste processing facility
15:59 Restarted transfer of processed water to buffer tank
July 10 (Sun)04:53 Shut down water treatment facility due to leakage of chemical liquid fromchemical injection line of coagulation settling equipment
12:11 Halted transfer of processed water to buffer tank due to drop in processedwater temporary tank water levels; however, contaminated water
processing and core injection continued to be carried out
15:15 Unit-3 Restarted transfer of puddle water in basement of turbine building
to collective waste processing facility
17:06 Repaired coagulation settling equipment leakage part, then started up
water treatment facility. Afterwards, achieved rated flow rate (17:40)
21:20 Restarted transfer of processed water to buffer tank
July 11 (Mon)
Operated diesel generators for dual-line preparation work for Yoru no Moripower lines
D/G 5A started up (03:03), synchronised (03:19), disconnected (09:07),
shut down (09:07) due to alarm activation
D/G 5B started up (03:37), synchronised (03:44), disconnected (13:18),
shut down (14:44)
D/G 6A started up (04:17), synchronised (04:21), disconnected (13:40),
shut down (15:42)
D/G 6B started up (04:31), synchronised (04:36), disconnected (13:44),
shut down (16:36)
05:01 Halted power reception from Yoru no Mori power lines due to dual-line
preparation work for Yoru no Mori power lines (-13:44)
10:00 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to mega float (-17:00)
32

10:30 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:30)
July 12 (Tue)08:51 Shut down water treatment facility due to leakage of chemical liquid fromchemical injection line connection part of coagulation settling equipment
11:00 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to mega float (-16:00)
11:22 Unit-4 Filled device storage pool (DSP) with water (-12:03)
16:28 Repaired coagulation settling equipment leakage part, then started up
water treatment facility
July 13 (Wed)06:30 Unit-5 Temporarily shut down RHR pump to exchange temporary RHRpump hose (-10:58)
08:40 Unit-6 Transferred puddle water in basement of reactor building to Unit-6
waste processing building (-10:50)
10:00 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to mega float (-17:00)
10:00 Unit-2 Began transferring puddle water in turbine building trench tocollective waste processing facility
10:09 Unit-4 Filled device storage pool (DSP) with water (-12:45)
11:00 Temporarily shut down water treatment facility operation due toadsorption tower vessel exchange (-July 14, 14:58)
13:07 Halted flushing of water treatment facility due to confirmation of leakage
from chemical injection line connection part of coagulation settlingequipment
16:22 Adjusted buffer tank transfer rate from 23m3/h to 18m3/h
July 14 (Thu)
05:30 Unit-1 Changed reactor injection ratio to 3.5m3/h due to injection ratio
decreasing to 3.2m3/h
July 15 (Fri)05:14 Shut down water treatment facility due to investigation of cause of flowrate decrease (-14:21)
10:00 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to mega float (-17:00)
10:50 Unit-3 Transferred puddle water in basement of turbine building tocollective waste processing facility
10:56 Unit-2 Transferred puddle water in turbine building trenches to collective
waste processing facility
13:05 Unit-4 Filled device storage pool (DSP) with water (-19:15)
14:25 Unit-5 Shut down RHR (C) pump
14:45 Unit-5 Started up RHR (D) pump
18:32 Transferred processed water from processed water temporary storagetank to buffer tank (-July 17, 03:20)
July 16 (Sat)33

Operated diesel generators for dual-line preparation work for Yoru no Moripower lines
D/G 5B started up (04:01), synchronised (04:12), disconnected (11:48),
shut down (13:05)
D/G 6B started up (04:21), synchronised (04:35), disconnected (12:05),
shut down (13:51)
05:28 Halted power reception from Yoru no Mori power lines due to dual-line
preparation work for Yoru no Mori power lines (-12:05)
10:00 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to mega float (-15:00)
10:50 Temporarily shut down water treatment facility operation due toadsorption tower vessel exchange
10:50 Unit-3 Transferred puddle water in basement of turbine building tocollective waste processing facility (- July 21, 15:59)
10:56 Unit-2 Transferred puddle water in turbine building trench to collective
waste processing facility (- July 21, 16:04)
11:22 Unit-4 Filled device storage pool (DSP) with water (-15:52)
July 17 (Sun)Operated diesel generators for dual-line preparation work for Yoru no Moripower lines
D/G 5B started up (03:08), synchronised (03:17), disconnected (14:14),
shut down (15:26)
D/G 6B started up (03:28), synchronised (03:40), disconnected (14:34),
shut down (16:02)
04:24 Halted power reception from Yoru no Mori power lines due to dual-line
preparation work for Yoru no Mori power lines (-13:20)
10:06 Unit-1 Alarm sounding (09:46) when injection ratio decreased to 3.0m3/h.
Changed reactor injection ratio to 3.8m3/h
14:25 Units-1, 2 Adjusted reactor injection ratio to 4.0m3/h after switching fromreactor injection pump 1 to reactor injection pump 2
July 18 (Mon)
08:30 Unit-3 Installed temporary roof over turbine building rooftop opening(-14:40)
09:00 Unit-6 Transferred puddle water in basement of reactor building to unit-6
waste processing building (-10:30)
11:00 Exchanged water treatment facility vessels (without shutting down water
treatment facility) (-14:59)
July 19 (Tue)
08:30 Unit-3 Installed temporary roof over turbine building rooftop opening(-15:00)
10:10 Units-1, 2 Adjusted reactor injection ratio to 3.8m3/h
11:00 Exchanged water treatment facility vessels (temporarily shut down water
treatment facility) (-15:03)
July 20 (Wed)34

11:15 Unit-4 Filled device storage pool (DSP) with water (-15:39)
July 21 (Thu)
08:38 Unit-3 Temporarily shut down alternative spent fuel pool cooling system
due to dual-line restoration work for Yoru no Mori power lines (-14:52)
08:38 Temporarily shut down water treatment facility operation due toadsorption tower vessel exchange (- July 22, 00:23)
08:40 Temporarily halted cooling of spent fuel pool due to dual-line restoration
work for Yoru no Mori power lines (-14:41)
11:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (- July 22, 18:00)
July 22 (Fri)
07:10 Temporarily halted cooling of spent fuel pool due to Okuma power line 2
circuit breaker shutdown (-10:40)
07:10 Unit-3 Temporarily shut down alternative spent fuel pool cooling system
due to Okuma power line 2 circuit breaker shutdown (-11:50)
07:10 Water treatment facility temporarily shut down due to Okuma power line 2
circuit breaker shutdown
08:30 Unit-3 Installed temporary roof over turbine building rooftop opening(-15:30)
08:43 Unit-2 Adjusted reactor injection ratio to 3.8m3/h due to it dropping to
3.4m3/h
16:53 Unit-3 Transferred puddle water in basement of turbine building tocollective waste processing facility (-July 29, 09:48)
16:56 Unit-2 Transferred puddle water in turbine building trench to collective
waste processing facility (-July 29, 09:43)
17:00 Replenished buffer tank with water from filtered water tank (-July 23,
11:04)
July 23 (Sat)03:24 Temporarily shut down alternative spent fuel pool cooling system due todual-line restoration work for Yoru no Mori power lines (-11:45)
03:46 Temporarily halted cooling of spent fuel pool due to dual-line restoration
work for Yoru no Mori power lines (-09:41)
08:45 Temporarily shut down water treatment facility due to dual-line restoration
work for Yoru no Mori power lines (-15:26)
09:35 Unit-2 Adjusted reactor injection ratio to 3.8m3/h after dropping to
3.2m3/h
11:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-18:00)
14:15 Transferred puddle water from miscellaneous solid waste reduction
processing building to process main building (-19:00)
18:10 Transferred processed water from processed water temporary tank tobuffer tank (-19:27)
July 24 (Sun)10:37 Unit-4 Filled device storage pool (DSP) with water (-15:20)
35

11:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:00)
11:10 Unit-1 Adjusted reactor injection ratio to 3.8m3/h after dropping to
3.3m3/h
11:27 Transferred processed water from processed water temporary tank tobuffer tank (-15:11)
12:30 Exchanged water treatment facility vessels (without shutting down water
treatment facility) (-16:35)
17:44 Replenished buffer tank with filtered water from filtered water tank due tobuffer tank water level nearing lower control values
20:00 Unit-1 Switched to supplies for nitrogen sealing of the PrimaryContainment Vessel (PCV) that was supplying from the compressor to
Units-2, 3
July 25 (Mon)
10:29 Exchanged water treatment facility vessels (without shutting down water
treatment facility) (-10:48)
12:29 Unit-2 Injected approx. 1m3 of hydrazine from alternative spent fuel poolcooling system to spent fuel pool (-13:27)
21:35 Temporarily shut down the pump in system 1 of cesium adsorption unit(-21:56)
July 26 (Tue)
09:59 Transferred puddle water from miscellaneous solid waste reduction
processing equipment to process main building (-16:01)
11:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-July 27, 16:00)
11:00 Unit-6 Transferred puddle water in basement of reactor building to unit-6
waste processing building (-12:00)
11:15 Unit-2 Injected approx. 1.2m3 of hydrazine from alternative spent fuel poolcooling system to spent fuel pool (-12:52)
11:37 Exchanged water treatment facility vessels (without shutting down water
treatment facility) (-14:06)
July 27 (Wed)08:45 Unit-6 Transferred puddle water in basement of reactor building totemporary tank (-11:20, 13:00 - 13:30)
10:00 Unit-6 Began transferring puddle water collected in the temporary tank,which had been in the basement of the turbine building, to mega float.
Later halted transfer due to transfer pump leakage (10:45). Exchangedtransfer pump (12:30 – 14:00). Approx. 20 liters leaked, but this leakedwater was not released into the ground or ocean.
11:06 Exchanged water treatment facility vessels (without shutting down water
treatment facility) (-11:28)
18:10 Unit-1 Adjusted core injection ratio to 3.8m3/h per one pump
18:10 Unit-2 Adjusted core injection ratio to 3.5m3/h per one pump
18:10 Unit-3 Adjusted core injection ratio to 9.0m3/h per one pump
36

July 28 (Thu)
10:00 Unit-6 Began transferring puddle water collected in the temporary tank,which had been in the basement of the turbine building, to mega float
11:00 Unit-4 Filled device storage pool (DSP) with water (-16:00)
11:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:00)
11:11 Exchanged water treatment facility vessels (without shutting down water
treatment facility) (-12:15)
17:30 Unit-2 Adjusted reactor injection ratio to 3.6m3/h since it had decreased to
3.2m3/hJuly 29 (Fri)05:08 Temporarily shut down the pump in a system of cesium adsorption unit
10:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-17:00)
10:03 Transferred puddle water from miscellaneous solid waste reduction
processing building to process main building (-16:09)
11:00 Exchanged water treatment facility vessels (without shutting down water
treatment facility) (-11:34)
11:55 Unit-3 Injected hydrazine from alternative spent fuel pool cooling system
to spent fuel pool (-13:29)
July 30 (Sat)10:00 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to mega float (-17:00)
11:00 Unit-6 Transferred puddle water in basement of turbine building totemporary tank (-16:00)
11:04 Transferred puddle water in basement of common spent fuel pool building
to fresh water processing unit upstream side receiving tank
11:12 Unit-3 Began injecting hydrazine from alternative spent fuel pool coolingsystem to spent fuel pool
11:30 Exchanged water treatment facility vessels (without shutting down water
treatment facility) (-13:35)
11:57 Unit-1 Adjusted reactor injection ratio to 3.6m3/h since it had decreased to
3.4m3/h
11:57 Unit-2 Adjusted reactor injection ratio to 3.6m3/h since it had decreased to
3.3m3/h
13:16 Unit-4 Filled device storage pool (DSP) with water (-14:47)
16:10 Unit-2 Transferred puddle water in turbine building trench to collective
waste processing facility
16:13 Unit-3 Transferred puddle water in basement of turbine building tocollective waste processing facility
July 31 (Sun)05:01 Unit-1 Adjusted reactor injection ratio to 3.7m3/h since it had decreased to
3.5m3/h37

05:01 Unit-2 Adjusted reactor injection ratio to 3.7m3/h since it had decreased to
3.2m3/h
10:00 Unit-6 Transferred puddle water collected in the temporary tank, which
had been in the basement of the turbine building, to mega float
11:00 Unit-6 Began transferring puddle water in basement of turbine building totemporary tank
13:58 Transferred puddle water from miscellaneous solid waste reduction
processing building to process main building(2) Tokyo Electric Power Company's 2F
March 11 (Fri)
14：48 The earthquake automatically shut down the unit-1～4.
17：35 Unit-1 Confirmed conditions should be reported under Article 10 of the
Nuclear Emergency Preparedness Act.
(Due to potential leakage of reactor coolant)
18：33 Units-1, 2, 4 Confirmed conditions should be reported under Article 10 of
the Nuclear Emergency Preparedness Act.
(Due to the Loss of the residual heat removal function)
March 12 (Sat)03:00 Units-1～4 Injected water to the reactor with condensate makeup water
system05：22 Unit-1 Confirmed conditions should be reported under Article 15 of the
Nuclear Emergency Preparedness Act.
（Due to the loss of the reactor pressure control function)
05：32 Unit-2 Confirmed conditions should be reported under Article 15 of the
Nuclear Emergency Preparedness Act.
（Due to the loss of the reactor pressure control function)
06：07 Unit-4 Confirmed conditions should be reported under Article 15 of the
Nuclear Emergency Preparedness Act.
（Due to the loss of the reactor pressure control function）
07：45 Declaration of nuclear emergency was announced:
According to Article 15 Paragraph 3 of the Nuclear Emergency
Preparedness Act, the prime minister instructed the evacuation of local
residents within 3km radius of 2F. Residents within 10km radius were
instructed to stay indoors.
12：15 Unit-3 reaches the state of cold shutdown.
17：39 The prime minister instructed the evacuation of local residents within
10km radius of 2F.
March 14 (Mon)
01:24 Unit-1 Restoration of reactor cooling function
07:13 Unit-2 Restoration of reactor cooling function
10：15 Unit-1 recovered from conditions that constitute an event requiring
reporting under Article 15 of the Nuclear Emergency Preparedness Act.
38

13：40 Unit-1 reached the state of cold shutdown.
14：20 Unit-2 reached the state of cold shutdown.
15:42 Unit-4 Restoration of reactor cooling function
15：52 Unit-2 recovered from conditions that constitute an event requiring
reporting under Article 15 of the Nuclear Emergency Preparedness Act.
21：58 Confirmed conditions of 2F should be reported under Article 10 of the
Nuclear Emergency Preparedness Act. (MP1).
（Due to an increase of radiation dose at the site’s boundary, which issuspected to be the effect of the situation at 1F)
March 15 (Tue)00：00 Confirmed conditions of 2F should be reported under Article 10 of the
Nuclear Emergency Preparedness Act. (MP3).
（Due to an increase of radiation dose at the site boundary, which issuspected to be the effect of the situation at 1F）
07：15 Unit-4 reaches the state of cold shutdown.
Unit-4 recovered from conditions that constitute an event requiring
reporting under Article 15 of the Nuclear Emergency Preparedness Act.
March 17 (Thu)
00：00 Unit-1, 2, 3 and 4 were in the state of cold shutdown.
March 18 (Fri)
17:50 NISA announced the results of temporarily rates of INES (International
Nuclear and Radiological Event Scale)・Unit-1, 2, 4: Level 3 (Serious Incident)
March 21 (Mon)
00:00 Ｕnit-1, 2, 3 ,4 were in the state of cold shutdown.
Unit 1 Reactor water level: 10,696mm
Unit 2 Reactor water level: 10,246mm
Unit 3 Reactor water level: 7,596mm
Unit 4 Reactor water level: 8,596mm
March 22 (Tue)00:00 Ｕnit-1, 2, 3, 4 were in the state of cold shutdown
Unit-1 reactor water level: 8,146mm
Unit-2 reactor water level: 10,246mm
Unit-3 reactor water level: 7,396mm
Unit-4 reactor water level: 8,096mm
March 24 (Thu)
00:00 Ｕnit-1, 2, 3, 4 were in the state of cold shutdown
Unit-1 reactor water level: 9,196mm
Unit-2 reactor water level: 10,296mm
Unit-3 reactor water level: 7,596mm
Unit-4 reactor water level: 8,796mm
March 30 (Wed)17：56 Smoke generation from around the 1st floor of the Turbine Building of unit1 was discovered. The incident was reported to the fire department.
39

（It was confirmed that there was no longer any smoke at 18：13.）
19：15 The fire department made a judgmental decision that this incident of unit1 was caused fault of the equipment, they found no signs of fire.
April 7 (Thu)
23:55 Units-1～4 No abnormalities in plant or waste processing building due toearthquake at around 23:32
April 11 (Mon)
17:45 Units-1～4 No abnormalities in plant or waste processing building due toearthquake at around 17:16
April 12 (Tue)
14:30 Units-1～4 No abnormalities in plant or waste processing building due toearthquake at around 14:07
April 16 (Sat)
11:38 Units-1～4 No abnormalities in plant or waste processing building due toearthquake at around 11:19
April 22 (Fri)00:00 Changed evacuation area from 10km radius to 8km radius(3) Tohoku Electric Power Company's Onagawa NPS
March 11 (Fri)
14：46 The earthquake automatically shut down Onagawa NPS unit-1～3.
Unit-1: The loss of off-site power led to the startup of emergency diesel
generators (failure of start-up transformer)
Unit-2 and 3: Receiving off-site power(Unit-2 was just after reactor start-up, being cold shut down)
15:30 Smoke was seen from the first basement floor of the turbine building.
17:15 CO2 fire extinguishers commenced.
22:55 Fire extinguishment was confirmed.
March 12 (Sat)00:58 Unit-2 reaches the state of cold shutdown.(under 100℃)
01:17 Unit-3 reaches the state of cold shutdown.(under 100℃)
As of 22:00 Unit-1 restored the start-up transformer and off-site power.
March 13 (Sun)12：50 Reported conditions of Onagawa NPS under Article 10 of the Nuclear
Emergency Preparedness Act.
(Although the radiation is not from Onagawa NPS, radiation level of thesite's boundary reached the criteria (5μSv/h). Temporally, it reached up
to 21μSv/h.)March 29 (Tue)The collapse of the outdoor heavy oil tank for auxiliary boiler of unit-1 by
Tsunami was reported under the Article 3 of the Ministerial Ordinance for
the Reports related to Electricity as it constitutes the breakage of a mainelectric facility.
40

The motors of pump for the component cooling water system and highpressure core spray system cooling water system of unit-2 were found tohave suffered water damage. They were transported to a factory for
inspection and subsequently confirmed that they could not longer be used.
This was reported under the Article 62-3 of the Nuclear Regulation Act.
April 1 (Fri)
10:40 Unit-1 Confirmed emergency diesel generator (A) could not connect tostation power systems during regular testing (deviation from LCO,
switched reactor cooling system to B system, LCO restored)
April 7 (Thu)
23:32 Earthquake occurred (seismic acceleration measured at Onagawa power
station: 476.3 Gal) Oshika Line line 1, Matsushima Line line 1, andTsukahama Line line 1 shut down. Receive power from Matsushima Line 1
line 1.
April 8 (Fri)08:08 Restoration of Oshika Line 2
08:31 Restoration of Oshika Line 1
09:22 Shut down Matsushima Line 1 for inspection
14:01 Restoration of Tsukahama Line
18:45 Restoration of Matsushima Line 1
April 10 (Sun)15:38 Restoration of Matsushima Line 2(4) Tohoku Electric Power Company's Higashidori NPSMarch 11 (Fri)
14:46 Loss of off-site power led to the startup of emergency diesel generators
while being in outage shutdown.
23:50 External power was restored.
(5) Japan Atomic Power Company's Tokai No.2
March 11 (Fri)
14：48 The earthquake automatically shut down(large turbine vibrations)
15:10 Reactor has reached under critical condition
March 13 (Sun)19:37 Back up power supply is restored.
Work to switch the station’s power supply to back up power wascompleted.
March 15 (Tue)00:40 Reached the state of cold shutdown.
March 18 (Fri)
15:00 Switched from back up power line to main power line
March 22 (Tue)41

22:10 3 emergency diesel generators restored to standby (since one of theseawater pumps had shut down due to the tsunami, one of theemergency diesel generators had been shut down.)
July 15 (Fri)
15:09 Unit-1 Emergency diesel generator (B) restored to standby condition due tocompletion of repairs
July 16 (Sat)
11:11 Unit-1 Restored reactor coolant purification system
July 17 (Sun)09:36 Unit-1 Temporarily shut down RHR (B) pump due to recirculation systemswitching work (-14:13)
11:04 Unit-1 Started up FPC (B) pump
11:40 Unit-2 Restored reactor coolant purification system
July 18 (Mon)
10:39 Unit-2 Temporarily shut down RHR (B) pump due to recirculation systemswitching work (-12:19)
11:33 Unit-2 Started up FPC system pump (A)End42