*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 4.8 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.
- At 10:23 on December 17, in the spent fuel pool alternative cooling 
  system, an alarm for "Air fin cooler panel malfunction" was triggered. 
  After the investigation at the site, it was confirmed that the secondary 
  system pressure decreased and the circulating pump (A) was shutdown 
  automatically. After the detailed investigation, it was confirmed that 
  the water leaked through the drainage line in the safety valve installed 
  in the upside of the pump (A). As the position of the handle of the 
  valve was off the usual position, we fixed it and at around 11:00 the 
  leaking stopped. After that, we increased the system pressure. 
  Confirming that no water leaked through the system, at 13:39, we 
  restarted the circulating pump (A) and cooling the spent fuel pool. The 
  leaked water from the drainage line is for the fire extinction purpose 
  (filtered water) and does not contain radioactive materials. The 
  temperature of the spent fuel at the cold shutdown and restart is 13°C 
  and no there is no temperature rising.

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. 2.8 m3/h from the reactor
  feed water system and approx. 5.9 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 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. 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. 

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 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, as we confirmed the system was operating normally, as we presume
  that the cause is stuck of dust in the pipe. At 4:00 pm on December 16,
  we stopped transferring the accumulated water in the tank.
- From 10:00 am on December 15 to 4:00 pm on December 16, we transferred
  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 10:04 am on December 17, we 
  stopped it. 
- At 10:12 on December 17, we started transferring accumulated water from 
  the basement of Unit 2 turbine building to Centralized Radiation Waste 
  Treatment Facility (Miscellaneous Solid Waste Volume Reduction Treatment 
  Building [High Temperature Incinerator Building] and Process Main 
  Building). At 12:24 pm on the same day, we stopped the transfer since 
  the water level at Unit 2 turbine building did not change. Then we 
  confirmed at the site that the switching valve of the transfer line was 
  closed and that there was no leakage from the line. Then we opened the 
  valve and restarted the transfer at 1:22 pm on the same day.