*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.
  The current water injection volume is approx 4.4m3/h from the reactor 
  feed water 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, we started injecting water to the reactor 
  through core spray system water injection piping arrangement in addition 
  to the water injection through reactor feed water system piping 
  arrangement.
  Water is currently injected at approx. 3.1m3/h through reactor feed water 
  system piping arrangement, and at approx. 4.3 m3/h through core spray 
  system water injection piping arrangement.
- 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 11:04 am on November 6, we started operation of radioactive material 
  decontamination instrument of spent fuel pool.
- 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. 
  Water is currently injected at approx. 2 m3/h through reactor feed water 
  system piping arrangement, and at approx. 6.1 m3/h through core spray 
  system water injection piping arrangement.
- 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.
- Regarding spent fuel pool for unit 4, from August 20 to November 8, we 
  had decreased salinity by using the desalting facility. In order to 
  decrease more salinity, we installed Ion exchange equipment and started 
  the equipment at 10:58 am on November 29.
- 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.
- From November 28, we started cleaning to avoid the performance 
  deterioration of pumps by sucking up sands etc. accumulated at the 
  bottom of the inlet canal pump room.
- 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 9:25 am on November 15, we started transfer of accumulated water from 
  basement of Unit 3 turbine building to Centralized Radiation Waste 
  Treatment Facility Building.
- 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.
- On December 2, as we finished the construction work to reinforce on-site 
  power, we stopped the evaporative concentration apparatus at 6:00 pm on 
  December 2, the water desalinations (reverse osmosis membrane type) at 
  8:04 am on December 3 and the cesium adsorption apparatus at 8:04 am on 
  December 3, respectively, in order to receive power from the power 
  source. As for the second cesium adsorption apparatus, it is operated 
  without interruption and the treatment of accumulated water is in 
  progress. There is no adverse effect to water injection into the reactor, 
  as purified water in the buffer tank is utilized. We restarted the water 
  desalinations (reverse osmosis membrane type) at 1:30 pm on December 3 
  and the cesium adsorption apparatus at 2:22 pm, and the evaporative 
  concentration apparatus at 2:34 pm, after power receiving operation.
- From around at 5:48 pm on December 3, data of monitoring post No.8, 
  monitoring dosage rate at the power station, found disappeared. As the 
  reason was not found and the post was not be able to recovered, an 
  alternative monitoring by monitoring post No.7 and a dose rate meter 
  having additionally monitored around monitoring post No, 8 (which was 
  set to monitor corresponding to nitrogen injection to RPV) was conducted, 
  and the most recent data was not changed from that of the day before 
  (The monitoring post No.7: 92μSv /hour, around the monitoring post 
  No. 8: 42μSv /hour (as of 8:00 pm) ). The monitoring post No.8 will be 
  maintained hereafter. 
- For works to stop of the leakage detected between cable duct for starting 
  transformer and control building of Unit 3, which was confirmed on August 
  4 (announced on August 8, 2011), we conducted switching power of power 
  panel from at 7:07 pm to 9:01 pm on December 3, to transfer and 
  disconnect cables of power panel of backup transformer, receiving power 
  from Okuma line 2L. Due to the switching work, lightings of rest houses 
  in the site, regional air-exhaust ventilators, dust monitors located at 
  main entrance, Main Anti-Earthquake Building, and rest houses of Unit 
  5/6 service building were stopped. After finishing switching works, the 
  abovementioned systems recovered.