* 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 4.5 m3/h from the reactor 
  feed water system and approx. 1.9 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. 2.6 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. 6.5 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 around 1 pm on December 22, it was found that the hose of Unit 3 
  Reactor Water Injection Line was swollen to the extent of 2 meter long. 
  Although there was no leakage from the swollen hose, it was decided that 
  the pump for Reactor water injection should be switched from the reactor 
  injection pump on the hill to the emergency motor pump and the hose 
  should be replaced with new one.(+) At 7:12 pm on the same day, the 
  emergency motor pump was started to operate. From 7:44 pm, the valve to 
  the normal water injection line was closed in order to weep drain from 
  the line. After the replacement of the hose, at 8:47 pm, the valve to  
  the normal water injection line was opened to fill water in the line. At 
  10 pm, it was confirmed that there was no water leakage from the new 
  hose, so that water injection to the Reactor was adjusted to about 3 
  m3/hour from Reactor Feed Water System and about 6 m3/hour from Reactor 
  Core Spray System at about 10:30 pm. At 10:38 pm, the emergency motor 
  pump was stopped. After that, it was checked that there was no leakage 
  from the hose and its connection. During the hose replacement work, the 
  water injection was continued and there was no remarkable change in 
  temperature of the Reactor Pressure Vessel.

  + Article 12 of Safety Regulation at Nuclear Facilities stipulates 
    "operational limit" and "required measures if the operational limit is 
    not satisfied" according to the facility management based on "the 
    mid-term view point for securing safety". It also stipulates to 
    respond based on the required measures if the operational limits is 
    not satisfied. In the case of today's hose swollen, it was regarded 
    to be sifted off the operational limit as planned (from 6:35 pm on 
    December 22 to 10:43 pm on the same day) from the proactive 
    maintenance point of view, so that the hose replacement work was 
    implemented accordingly.

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.
- From 1:57 pm on December 21 to 9:42 am on December 23, transfer of 
  accumulated water was implemented 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).