*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.
  The current water injection volume is approx 4.4 m3/h from the reactor 
  feed water system and approx. 1.8 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. 
  At 10:20 pm on December 11, we stopped the alternative cooling equipment 
  for spent fuel pool, in order to conduct power source changeover work for 
  improving power supply reliability. At 5:07 pm on December 12, it was 
  resumed after the completion of power source changeover work. The 
  temperature of the pool was 14 degrees at the time of suspension, and it 
  was 15 degrees at the time of resumption. 
- 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 2.6 m3/h from the reactor 
  feed water system and approx. 6.1 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. 
  At 3:53 pm on December 12, the annunciator alerted for the Unit 2 SFP 
  alternative cooling system, which showed the difference between inlet and 
  outlet flow at the primary pump exceeded the limit. Any abnormalities 
  like water leakage were not observed by patrolling at the site. Currently 
  the automatic trip system by the annunciator is temporarily removed, and 
  monitoring the level of the skimmer surge tank is enhanced as the 
  alternative monitoring measure. The cooling system will be manually 
  tripped if there are abnormalities on the skimmer surge tank level, which 
  is confirmed there is no change on the level. At 5:18 pm, after vibrated 
  the instrument piping, it was confirmed the annunciator was cleared. It 
  is planned to enhance the monitoring after the inspection of flow meters 
  and the flushing of detection lines. There is no problem on the SFP 
  cooling as the alternative cooling system is continuously operated. 
- 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.
- 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. 6.1 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. 

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. 
- From 10 am to 4 pm on December 12, we conducted transferring of 
  accumulated water from the Turbine Building of Unit 6 to the temporary 
  tank. At 10 am on December 13, we started transferring of accumulated 
  water. 
- At around 4 pm on December 12, it was found the water spilled from the 
  bucket, which was used to collect drain water from sampling line of the 
  evaporative condensation apparatus 3C. The paddle water was spread around 
  1 meter radius from the bucket (the capacity of the bucket: approx. 7 
  liters, spilled water: approx. 3 liters), which stayed inside the barrier. 
  At around 7:30 pm, when replaced the bucket to new one, it was confirmed 
  that there was no leakage form the valve of the sampling line. At around 
  8:30 pm, when patrolling at the site, it was found that the water spilled 
  from the bucket again. The paddle water was then spread around 1.5 meter 
  radius (the capacity of the second bucket: approx. 12 liters, spilled 
  water: 7 liters), which stayed inside the barrier, too. At around 8:50 pm, 
  the valve of the sampling line was tightly closed as it was found that 
  the valve was not completely closed, and it was confirmed there was no 
  water leakage. Around 10:25 pm, the inlet and outlet valve of the pump 
  was closed for pre-caution. The same operation was done for 3A and 3B of 
  the evaporative condensation apparatuses. At around 11:40 pm, it was 
  confirmed that there was no additional leakage at the site. 
- On December 4, it was found that puddle water inside the barrier around 
  the evaporative condensation apparatus 3A to 3C was leaked through the 
  crack at the concrete floor widened by the deformation of the sealing 
  material. Afterwards the similar places were inspected, and then the 
  damage of the concrete floor was found around the evaporative 
  condensation apparatus 1A to 1C. On December 6, the repair work of the 
  concrete floor was completed. The leak water detection device will be 
  installed inside the barrier by December 15 as one of the measures for 
  preventing the recurrence of such leakage, in addition to the patrolling 
  six times a day until the device will be installed. Upon the preventing 
  measures are prepared, and considering the water mass balance, the 
  evaporative condensation apparatuses 1B, 1C and 1A were re-started on 
  2:33 pm, 2:46 pm and 3:50 pm on December 12, respectively.