*Updates are underlined. 

All 6 units of Fukushima Daiichi Nuclear Power Station have been shut down. 

Unit 1 (Shut down) 
- Explosive sound and white smoke were confirmed after the big quake 
  occurred at 3:36 pm on March 12. It was assumed to be hydrogen explosion.
- At 3:37 pm on March 25, we started injecting freshwater to the reactor 
  and are now injecting fresh water by a motor driven pump powered by the 
  off-site transmission line. 
- At 10:11 am on December 10, in addition to water injection from water 
  feeding system, we started water injection from piping of core spray 
  system to the reactor.
  At 9:40 am on December 16, as the decreasing of injecting water was 
  confirmed, we adjusted injection rate of core spray system from approx.
  1.6m3/hour to approx.2m3 /hour. 
  The current water injection volume is approx 4.5 m3/h from the reactor 
  feed water system and approx. 2.0 m3/h from the core spray system.
- We commenced injection of nitrogen gas into Primary Containment Vessel at 
  1:31 am on April 7.
- At 11:22 am on August 10, we started cyclic cooling for the water in the 
  spent fuel pool by an alternative cooling equipment of the Fuel Pool 
  Cooling and Filtering System. 
- On October 28, we completed installation of the cover for the Reactor 
  Building in order to contain dispersion of radioactive substances.
- At 4:04 pm on November 30, we started operation to inject nitrogen into 
  the reactor pressure vessel. 

Unit 2 (Shut down) 
- At approximately 6:00 am on March 15, an abnormal noise began emanating 
  from nearby Pressure Suppression Chamber and the pressure within the 
  chamber decreased. 
- At 10:10 am on March 26, we started injecting freshwater to the reactor 
  and are now injecting fresh water by a motor driven pump powered by the 
  off-site transmission line. 
- At 2:59 pm on September 14, in addition to water injection from water 
  feeding system, we started water injection from piping of core spray 
  system to the reactor.
  The current water injection volume is approx. 2.9 m3/h from the reactor 
  feed water system and approx. 6.0 m3/h from the core spray system.  
- At 5:21 pm on May 31, we started cyclic cooling for the water in the 
  spent fuel pool by an alternative cooling equipment of the Fuel Pool 
  Cooling and Filtering System. 
  6:54 am on December 14, the alert that indicates the flow difference is 
  big at the inlet and outlet of primary pump was issued on the alternative 
  cooling system of sent fuel pool. No abnormalities such as leaking etc. 
  were found by field inspection. Then, as we sounded the instrument piping, 
  we confirmed that alert stopped. Hereafter we will check flow rate once 
  an hour. In addition to this, keeping operation of spent fuel pool 
  alternative cooling system so there is no problem on cooling   
- At 8:06 pm on June 28, we started injecting nitrogen gas into the Primary 
  Containment Vessel.
- From 6:00 pm on October 28, we put the gas management system of the 
  reactor containment vessel in operation.
- On December 15 we conducted air sampling at the gas controlling system of 
  the Primary Containment Vessel of unit 2. As a result we confirmed that 
  at the exit of the gas controlling system of the Primary Containment 
  Vessel, the level of xe-135 detected was below detection limit (9.1 x 
  10-2Bq/cm3) and below the recriticality standard 1Bq/cm3.
- At 10:46 am on December 1, we started the nitrogen injection to the 
  Reactor Pressure Vessel. 

Unit 3 (Shut down) 
- Explosive sound and white smoke were confirmed at approximately 11:01 am 
  on March 14. It was assumed to be hydrogen explosion.
- At 6:02 pm on March 25, we started injecting fresh water to the reactor 
  and are now injecting fresh water by a motor driven pump powered by the 
  off-site transmission line.
- At 2:58 pm on September 1, we started water injection by core spray 
  system in addition to water injection by the reactor feed water system 
  piping arrangement. 
  The current water injection volume is approx 2.8 m3/h from the reactor 
  feed water system and approx. 5.8 m3/h from the core spray system.
- At 7:47 pm on June 30, we started cyclic cooling for the water in the 
  spent fuel pool by an alternative cooling equipment of the Fuel Pool 
  Cooling and Filtering System.
- At 8:01 pm on July 14, injection of nitrogen gas into the Primary 
  Containment Vessel started. 
- At 4:26 pm on November 30, we started operation to inject nitrogen into 
  the reactor pressure vessel. 

Unit 4 (Outage due to regular inspection) 
- At around 6 am on March 15, we confirmed the explosive sound and the 
  sustained damage around the 5th floor rooftop area of Reactor Building.
- At 12:44 pm on July 31, we started cyclic cooling for the water in the 
  spent fuel pool by an alternative cooling equipment of the Fuel Pool 
  Cooling and Filtering System.
- At 10:58 am on November 29, in order to decrease more salinity, we 
  installed Ion exchange equipment and started the operation of such 
  equipment.
- At this moment, we don't think there is any reactor coolant leakage 
  inside the primary containment vessel. 

Unit 5 (Outage due to regular inspection) 
- Sufficient level of reactor coolant to ensure safety is maintained.
- At 5:00 am on March 19, we started the Residual Heat Removal System Pump 
  in order to cool the spent fuel pool.
- At 2:30 pm on March 20, the reactor achieved cold shutdown.
- At 2:45 pm on July 15, we started the operation of the original Residual 
  Heat Removal System (System B) by its original seawater pump.
- At this moment, we don't think there is any reactor coolant leakage 
  inside the primary containment vessel.
- With recovery work of residual heat removal sea water pump (B) which was 
  unavailable caused by Tsunami, we stopped residual heat removal pump (B) 
  and residual heat removal sea water pump (D) sequentially from 6:29 am on 
  December 14. The stop time will be approx. 10 hours and we expect that 
  the elevation of temperature is about 1.6 degree C/ hour, so we expected 
  there is no impact on reactor. (The temperature of the reactor core at 
  the time of suspension was 26.5 °C) After completion of the work, we 
  started the suspended pumps, and at 4:29 pm on the same day, we restarted 
  cooling the reactor. (The temperature of the reactor core at the time of 
  suspension was 26.5 °C and the temperature at the time of restart was 
  38.2 °C) 

Unit 6 (Outage due to regular inspection) 
- Sufficient level of reactor coolant to ensure safety is maintained.
- At 10:14 pm on March 19, we started the Residual Heat Removal System Pump 
  of Unit 6 to cool down Spent Fuel Pool.
- At 7:27 pm on March 20, the reactor achieved cold shutdown. 
- At 2:33 pm on September 15, we started separately cooling the reactor 
  through the Residual Heat Removal System and the spent fuel pool through 
  Equipment Cooling Water System and Fuel Pool Cooling System.
- At this moment, we do not think there is any reactor coolant leakage 
  inside PCV. 

Others 
- At around 10 am on June 13, we started the operation of the circulating 
  seawater purification facility installed at the screen area of Unit 2 
  and 3.
- At 8 pm on June 17, we started operation of Water Treatment Facility 
  against the accumulated water. At 6:00 pm on July 2, we started the 
  circulating injection cooling to inject the water, which was treated by 
  the accumulated water treatment system, to the reactors through the 
  buffer tank.
- At 7:41 pm on August 19, we started treatment of accumulated water by 
  parallel operation of one line from the cesium adsorption instrument to 
  the decontamination instrument and the other treatment line of the cesium 
  adsorption instrument No.2. 
- At 2:06 pm on October 7, we started to spray purified accumulated water 
  brought from Unit 5 and 6 continually in order to prevent dust scattering 
  and potential fire outbreaks from the cut down trees.
- On October 28, we started installation of the water proof wall at the sea 
  side, in front of the existing shore protection, Units 1-4, in order to 
  contain marine pollution by underground water.
- At 6:03 pm on November 30, we started transfer of the accumulated water 
  from the basement of Unit 2 turbine building to Centralized Radiation 
  Waste Treatment Facility High Temperature Incinerator Building. At 7:51 
  am on December 13, we stopped the transfer of the accumulated water from 
  the basement of Turbine Building of Unit 2 to the centralized radiation 
  waste treatment facility (miscellaneous solid waste Volume reduction 
  treatment building [high temperature incinerator building]) in order to 
  stop power supply to Unit 2 accumulated water transfer pump for power 
  supply enhancing work. With the stoppage of the water transfer, the 2nd 
  Cesium adsorption apparatus was shutdowned for replacing vessels at 8:44 
  am on December 12, and will be kept outage until December 14 in order to 
  adjust the water level of the centralized radiation waste treatment 
  facility (miscellaneous solid waste Volume reduction treatment building 
  [high temperature incinerator building]). The Cesium adsorption apparatus 
  is continued its operation. Water injection to the Reactors will not be 
  affected since the cooling is continued by using processed water in the 
  buffer tank.
- At 12:25 pm on December 13, we started the re-circulating operation of 
  desalination facility (reverse osmosis membrane type) for the purpose of 
  suppression of condensed water after desalination treatment.
- We plan to establish the system injecting water into the reactor in Unit 
  1 to 3 using the condensate storage tank of Unit 3. In preparation of 
  such establishment, the stored water in the tank was transferred to the 
  basement of turbine building of Unit 3 from 10:22 am on November 21 to 
  9:45 am on November 24. As the calibration of water level gauge is 
  required if all the water is transferred, approx. 200 ton was left in the 
  tank. During the measurement of salt concentration in the left water, it 
  turned out that concentration was high. In order to secure the space for 
  additional water injection to decrease such concentration, at 10:00 am on 
  December 6, the left water was transferred from the tank to the basement 
  of the turbine building of Unit 3.
  At 8:54 on December 7, we stopped transferring, and at approx. 9:19 am on 
  the same day, we started filling water in the tank, but afterwards, we 
  confirmed water leakage (approx. 5 liter) at the joint section of hose 
  connecting to the tank, at approx. 9:52 am, we stopped filling water and 
  confirmed the leakage has stopped. We plan to consider such measures as 
  repair etc. in future. The leaked water was treated as to be free of 
  radioactive materials and desalinated. At 9:05 am on December 9, we 
  restarted filling the water in the tank after completing the replacement 
  of the transfer hose. At 7:00 pm on the same day, we finished the filing. 
  At 9:30 am on December 12, we started transferring of the accumulated 
  water in the condensate storage tank of Unit 3 to the basement of Turbine 
  Building of Unit 3 before feeding water to reduce salt level in the tank. 
  After that we confirmed decrease of transferring quantity of water from 
  the water level fluctuation, at 0:00 pm on December 14, we stopped 
  transferring of the accumulated water in the tank. Also we confirmed that 
  there was no water leakage at the site. Currently we are investigating 
  the cause.
  At 0:30 pm on December 15, we flushed the pipe and started the system. 
  Then, we confirmed the system was operating normally. We will monitor the 
  status of the system operation. We considered the cause is stuck of dust 
  in the pipe. 
- At 10:00 am on December 15, we started transferring accumulated water 
  from the Turbine Building of Unit 6 to the temporary tank. 
- At 2:22 pm on December 15, we started transferring accumulated water from 
  the basement of Unit 3 turbine building to Centralized Radiation Waste 
  Facility (Process Main Building).
- At 9:10 am on December 15, a cooperative firm worker discovered the burnt 
  trace in the distribution panel at Centralized Waste Treatment Facility 
  (Miscellaneous Solid Waste Volume Reduction Treatment Building [High 
  Temperature Incinerator Building]). But a smoke was not found. We 
  reported the incident to the fire station at 9:19 am on the same day. At 
  10:28, we stopped power supply to the distribution panel. Afterwards, as 
  the result of confirmation at the site of this facility by fire station, 
  it is considered that the fire was not occurred. At 2:30 pm, we resumed 
  power supply to the distribution panel. 
- At 11:38 am on December 16, as we found that there was high vibration at 
  desalination plant (RO) unit 2-2 high pressure pomp, we manually stopped 
  the desalination plant. We confirmed that there is no water leakage at 
  the site. 
  We will study on its countermeasure later. On the other hand, 
  desalination plant (RO) unit 2-1 is in operation. And water injection to 
  the Reactors will not be affected since the cooling is continued by using 
  processed water in the buffer tank.