* 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.
  Current water injection volume is approx. 4.4 m3/h from the reactor feed 
  water system and approx. 2 m3/h from the core spray system.
- At 1:31 am on April 7, we commenced injection of nitrogen gas into 
  Primary Containment Vessel.
- 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.
- At 6:00 pm on December 19, a full-scale operation of the PCV gas 
  management system started. 

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.
  Current water injection amount is approx.2.0 m3/h in feed water system 
  and approx.7.0 m3/h in corer 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 8:06 pm on June 28, we started injecting nitrogen gas into the Primary 
  Containment Vessel.
- At 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 3 m3/h from the reactor feed 
  water system and approx. 6 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.
  Since inlet pressure of the primary circulation pump in the alternative 
  cooling system of the spent fuel pool frequently tended to decrease due 
  to the effect of clogging of the inlet strainer of the pump, the pump was 
  stopped at each time in order to flush the strainer. However, since this 
  tendency is supposed to continue and the temperature of the spent fuel 
  pool is sufficiently low, which is approx. 13.0°C, and there is enough 
  margin from the operational limit value (upper limit) by the safety 
  regulation, which is 65.0°C, we determined to stop the pump by January 4 
  of 2012 and temporary stop the cooling of spent fuel pool, considering 
  the exposure dose during the flushing.
  At 4:54 pm on December 30 of 2011, the pump was stopped. (Temperature of 
  the spent fuel pool was approx. 13.3°C at the time of shutdown.) It is 
  valuated that the temperature rise of the spent fuel pool due to the 
  shutdown of the pump is approx. 5 to 6 degrees for a day. And it is 
  planned that this pump operates for one time in a day to check the 
  temperature of the spent fuel pool during this temporary operation, since 
  December 31, 2011.
- 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 2:45 pm on July 15, we started the operation of the original Residual 
  Heat Removal System (System B) by its original seawater pump.
- At 10:11 am on December 22, since we finished the recovery work of 
  seawater pump (System B) of equipment water cooling system, we made a 
  trial run. At 11:25 am on the same day, we confirmed no abnormalities and 
  restarted the operation.
- 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 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 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.
- Since December 22, the atmospheric temperatures at point C of Unit 1 
  Primary Containment Vessel (PCV) monitored by the Containment Atmospheric 
  Monitoring System had risen (the atmospheric temperature of the PCV on 
  December 22 was approx. 38°C, at 7 pm on December 27 was approx. 49°C).  
  The other temperatures had not risen, so we conducted a survey checking 
  the reliability of the meters from 9 am to 10 am on December 28, and we 
  confirmed that there are no problems.  From 11:00am to 12:15pm on the 
  same day, we adjusted the volume of Nitrogen injection, from approx. 8 
  Nm3/h to approx.18 Nm3/h, and emission of the gas management system, from 
  approx. 23 Nm3/h to approx.30 Nm3/h, in order to identify the cause by 
  monitoring the system with the same injection and emission volume as 
  before December 22. The temperature went up to approx. 54.6°C at 6:00 pm 
  on December 28 at its maximum and fell to approx. 45.9°C at 11:00 am on 
  December 31. Temperatures at other two points also indicated slight 
  increases but are currently in the stable status. 
   Point D: (Maximum) approx. 35.8°C at 5:00 pm on December 29 → 
            approx. 33.4°C at 11:00 am on December 31. 
   Point E: (Maximum) approx. 40.0°C at 5:00 pm on December 29 → 
            approx. 36.9°C at 11:00 am on December 31. 
  We will continuously conduct the survey for the cause of temperature 
  increase and surveillance of the plant. 
- At 3:22 pm on December 28, we started to transfer 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] and the 
  Process Main Building).
- From 2:37 pm on December 30 to 9:58 am on December 31, we transferred the 
  accumulated water from the basement of turbine building of Unit 3 to the 
  Centralized Radiation Waste Treatment Facility (the Miscellaneous Solid 
  Waste Volume Reduction Treatment Building [High Temperature Incinerator 
  Building] and the Process Main Building).