* 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.
  At 5:05 am of December 21, decrease in water injection was confirmed and
  we adjusted water injection from the reactor feed water system from
  approx 4.3 m3/h to 4.5 m3/h, and water injection from the core spray
  system from approx. 1.8 m3/h to 2.0 m3/h.
  The current water injection volume is approx 4.5 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 6:00 pm on December 19, a full-scale operation of the PCV gas control
  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.
  The current water injection volume is approx. 2.8 m3/h from the reactor
  feed water system and approx. 6 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 3:03 pm on December 20, we stopped this system due to inspections in
  the flow rate detector of the alternative cooling equipment of the Fuel
  Pool. This is scheduled to last until around 2:00 pm of December 23 and
  during this time we are expecting that the temperature of the spent fuel
  pool will rise by 21 °C ( temperature at the time the we stopped the
  system: 15.4 °C).
- 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 2.9m3/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.
- 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.
- At 9:43 am on December 22, At the Alternative Cooling apparatus of Spent 
  Fuel Pool Cooling and Filtering System, since the suction force of 
  primary circulating pump decreased, we stopped the pump to conduct 
  flushing of entrance-side strainer of primary circulating pump and 
  stopped cooling of spent fuel pool. (The temperature of pool is approx. 
  13°C at that time) 

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 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.
- At 1:57 pm on December 21, transfer of accumulated water was started
  from Unit 2 turbine building to the Centralized Radiation Waste
  Treatment Facility (Miscellaneous Solid Waste Volume Reduction Treatment
  Building [High Temperature Incinerator Building] and Process Main
  Building).
- At around 1:40 am on December 21, the alarm went off at the desalination
  facility (reverse osmosis membrane type) 2-2 which showed that the
  closing of the backwash water drain valve of the multimedia filter was
  not conducted within the designated time, which led to an automatic
  shutdown of the unit. We confirmed at the site that there was no water
  leak. Since we have enough desalinated water this will not influence the
  water injection. Desalination facility (reverse osmosis membrane type) 3
  can be activated. Then, as the result of valve activity confirmation 
  investigation, there is no fault in the facilities. Therefore, we 
  considered the phenomenon is transient. At around 10:20 am on the same 
  day, we restarted the unit. We will continue to monitor operation status. 
- At 10:00 am on December 22, we started to replace the transmission parts 
  of monitoring post No.2 and No.8 which monitor dose rate inside the site. 
  In addition, monitoring post No.8 is stopped about 30 minutes due to the 
  replacement work. (Monitoring post No.2 is not stopped because of the 
  difference from No.8 replacement parts)