*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 5.5 m3/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.
 
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. 2.9 m3/h through reactor feed 
  water system piping arrangement, and at approx. 7.1 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.
- On November 22, we sampled gases in gas management system in primary 
  containment vessel of Unit 2 to analyze nuclides.  As a result of 
  nuclides analysis, we evaluated that there is no recriticality since the 
  density of Xe-135 is below the detection limits (1.1x10-1 Bq/cm3) and 
  that indicates the analyzed figure is below the determination criteria 
  for recriticality such as 1 Bq/cm3. Regarding Xe-135, we decided to use 
  the sampling result at gas vial container at inlet in gas management 
  system to evaluate the recriticality based on the "Report with regard to 
  "Policy on the mid term security" for the Units 1 to 4 of Fukushima 
  Daiichi Nuclear Power Station to Nuclear and Industrial Safety Agency at 
  the Ministry of Economy, Trade and Industry (1) (revision)" (Press 
  released on November 9th) because charcoal filter was used to detect 
  Xe-135 and we evaluated that they are created by spontaneous fission. 
  * Detection Limits  Charcoal Filter: Order of 10-6, Gas Vial Container: 
    Order of 10-1 
- At 11:04 am on November 6, we started operation of radioactive material 
  decontamination instrument of spent fuel pool.
 
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. 2.3 m3/h through reactor feed 
  water system piping arrangement, and at approx. 8.2 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.
 
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. (Hydrazine was also injected from 1:15 pm 
  to 2:50 pm on November 17)
- At 11:34 am on August 20, we started an operation of desalination 
  equipment in the spent fuel pool.
- 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 time, we don't think there is any reactor coolant leakage inside 
  the primary containment vessel. 
- From November 15, we started to cleanup work in order to prevent 
  performance deterioration of pump caused by inletting sand or other 
  materials piled up at the bottom of pump room of intake channel.
 
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 9:10 am on November 10, we started transfer of accumulated water from 
  the basement of Unit 2 turbine building to Centralized Radiation Waste 
  Treatment Facility High Temperature Incinerator Building.
- 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.
- As part of improving the liability of water injection into the reactors, 
  we plan to build reactor water injection facilities at Units 1 to 3. From 
  10:22 am on November 21, we started transferring the stored water from 
  the condensate storage tank to basement of turbine building of Unit 3
- At 10:47 pm on November 18, alarm occurred indicating high pressure of 
  treated water, and desalination plant (RO) unit 2-2 suspended due to 
  automatic suspend of a high pressure pump and a booster pump.  There is 
  no impact for water injection to the reactor because of enough fresh 
  water stock.  On November 22, we checked outside of the unit and found no 
  trouble, and so we remove the discharged water in drain line at exit side 
  of the Unit and reset the alarm.  At 2:00 pm on the same day, we 
  restarted the Unit.  While we had been checking the operation of the Unit, 
  at 9:56 am on November 23, the alarm occurred again indicating the high 
  pressure of treated water at the exit side of Unit2-2, and the unit 
  stopped automatically.  We are now investigating the reason of this 
  incident.  There is no impact for water injection to the reactor because 
  of enough fresh water stock. 
- At around 0:15 pm on November 23, when we started desalination plant (RO) 
  unit 1A and 1B to check whether water flows the system properly or not, 
  we found exit side of piping of the units broke and leakage of treatment 
  water in dam, and so we immediately stopped operation of the units.  The 
  amount of leakage from unit 1A and 1B are about 14 litters and 15 litters 
  respectively, and now it already stopped leaking.   We are now 
  investigating the reason of this incident.  There is no impact for water 
  injection to the reactor because desalination plant (RO) unit 2-1 and 3-1 
  are still operating and there are also enough fresh water stock.