* 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 pm on December 28 at
  its maximum and fell to approx. 46.4°C at 5:00 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. 33.6°C at 5:00 am on December 31. 
   Point E: (Maximum) approx. 40.0°C at 5:00 pm on December 29 →
              approx. 37.2°C at 5:00 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).