* 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. 

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. 
  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.
- 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 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, 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).