* The 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, 2011. It was assumed to be hydrogen 
  explosion. 
- At 3:37 pm on March 25, 2011, 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, 2011, 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 amount from the reactor feed water system is 
  approx. 4.5 m3/h and that from the core spray system is approx. 1.7 m3/h. 
- At 1:31 am on April 7, 2011, we commenced injection of nitrogen gas into 
  Primary Containment Vessel. 
  At 9:40 am on February 24, we started the work to add the flow-meters to 
  the nitrogen injection line at the side of Primary Containment Vessel of 
  Unit 1 in order to improve the reliability of nitrogen injection 
  activity. Due to this work, we suspended the nitrogen injection task 
  temporarily (*). After the completion of the installation, we restarted 
  the nitrogen injection. At 1:10 pm, it was confirmed that there was no 
  significant variation in the parameters. 
  * In the Chapter 12 of Nuclear Reactor Facilities Security Regulation 
    "The Way of Ensuring Mid-term Security", as the treatments like 
    "Operational limitation" or "Measures required in case of not 
    satisfying the operational limitation" are determined, it is supposed 
    the operator act per the required measures if it fails to satisfy the 
    operational limitation. This time, to implement maintenance works, we 
    have suspended the work of nitrogen injection at the side of Primary 
    Containment Vessel of Unit 1 by conducting a planned shift beyond the 
    range of operational limitation (from 9:40 am to 1:10 pm on 
    February 24). 
- At 11:22 am on August 10, 2011, 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, 2011, 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, 2011, we started operation to inject nitrogen 
  into the reactor pressure vessel. 
- At 6:00 pm on December 19, 2011, a full-scale operation of the PCV gas 
  management system started. 
 
 Unit 2 (Shut down) 
- At approximately 6:00 am on March 15, 2011, an abnormal noise began 
  emanating from nearby Pressure Suppression Chamber and the pressure 
  within the chamber decreased. 
- At 10:10 am on March 26, 2011, 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, 2011, in addition to water injection from 
  feed water system, we started water injection from piping of core spray 
  system to the reactor. 
- With regard to the water injection volume for Unit 2 reactor, which was 
  increased with temperature figure raising, we have gradually adjusted it 
  to the original volume before temperature increasing (Feed water system: 
  approx. 3.0m3/h, core spray system: approx. 6.0m3/h). During our 
  observing the plant parameter after decreasing the flow rate of feed 
  water system on February 22, we found that one thermometer in the lower 
  part of the RPV (top of the lower head 135°) indicated the different 
  movement from others. From 0:21 pm to 2:48 pm on February 23, we 
  investigated the concerned device. As the result of the measurement of 
  DC resistance, we found no breaking wire and availability of the 
  thermometer. But we confirmed that the DC resistance of it became higher 
  than the previous measurement test data. We will evaluate the soundness 
  of the concerned device and examine correspondence in future. We make 
  sure no re-criticality state because there were no significant changes 
  at the monitoring post and as the result of the sampling for the Gas 
  Control System of the Unit 2, we confirmed that the concentration of 
  Xe-135 was below the detectible limit. 
   ·At 11:00 am on February 24, the temperature of the lower part of the 
    RPV (top of the lower head)(135°) : approximate 47.1 °C 
   (Reference) 
   ·At 11:00 am on February 24, the temperature of the lower part of the 
    RPV (top of the lower head)(270°) : approximate 38.5 °C 
  The current water injection amount from the reactor feed water system is 
  approx. 2.9m3/h and that from the core spray system is approx. 6.0 m3/h. 
- At 5:21 pm on May 31, 2011, 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, 2011, we started injecting nitrogen gas into the 
  Primary Containment Vessel. 
- At 6:00 pm on October 28, 2011, a full operation of the PCV gas control 
  system started. 
- At 10:46 am on December 1, 2011, we started the nitrogen injection to 
  the Reactor Pressure Vessel. 
- At 11:50 am on January 19, 2012, we started the operation of the spent 
  fuel pool desalting facility. 
 
 Unit 3 (Shut down) 
- Explosive sound and white smoke were confirmed at approximately 11:01 am 
  on March 14, 2011. It was assumed to be hydrogen explosion. 
- At 6:02 pm on March 25, 2011, 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, 2011, we started water injection by core 
  spray system in addition to water injection by the reactor feed water 
  system piping arrangement. 
  At 10:05 am on February 24, as the change in the injected water amount 
  was observed, the injected water amount was adjusted from approx. 1.6 
  m3/h to 2.0m3/h in the feed water system and from approx. 5.2m3/h to 5.0 
  m3/h in the core spray system. 
  The current water injection amount from the reactor feed water system is 
  approx. 2.0m3/h and that from the core spray system is approx. 5.0 m3/h. 
- At 7:47 pm on June 30, 2011, 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, 2011, injection of nitrogen gas into the Primary 
  Containment Vessel started. 
- As installation works of the PCV gas control system was completed, we 
  started a test operation at 11:38 am on February 23, 2012. We confirmed 
  that an exhaust flow amount was stable at 33Nm3/h at 2:10 pm and started 
  an adjustment operation. 
- At 4:26 pm on November 30, 2011, we started operation to inject nitrogen 
  into the reactor pressure vessel. 
- At 3:18 pm on January 14, we started operation of the radioactive 
  material removal instrument for the spent fuel pool in Unit 3 
 
 Unit 4 (Outage due to regular inspection) 
- At around 6 am on March 15, 2011, 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, 2011, 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 3:11 pm on February 23, in the alternative cooling system of the 
  spent fuel pool of Unit 4, as the inhale pressure of the primary 
  circulating pump showed the tendency of decrease, we stopped the pump in 
  order to conduct flushing of the strainer on its entry side and 
  suspended cooling of the spent fuel pool (the temperature of the pool at 
  the time of the suspension was approx. 25°C) After the flushing, at 5:18 
  pm on the same day we resumed the cooling of the spent fuel pool and 
  confirmed the recovery of the inhale pressure of the pump. (the 
  temperature of the pool at the time of the resuming was approx. 26°C) 
- At 10:58 am on November 29, 2011, 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, 2011, we started the Residual Heat Removal 
  System Pump in order to cool the spent fuel pool. 
- At 2:45 pm on July 15, 2011, 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, 2011, 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 6:00 am on February 24, in order to change the delivery valve of the 
  pump (A) of the reactor sea water system of Unit 5, we stopped the pump 
  (C) of the reactor sea water system. As a result, the cooling of the 
  spent fuel pool was stopped. (the temperature of the spent fuel pool at 
  the time : approx 17.4°C) At 12:08 pm on the same day, the system was 
  restarted after the completion of the work. Accordingly the cooling of 
  the spent fuel pool was restarted as well. (pool temperature at the time 
  of the cooling restart: approx 18.2°C) 
- 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, 2011, we started the Residual Heat Removal 
  System Pump of Unit 6 to cool down Spent Fuel Pool. 
- At 2:33 pm on September 15, 2011, 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. 
- As the component cooling sea water system pump (C) of Unit 6 has been 
  restored, we started test operation at 10:05 am on February 22, 2012. 
  Accordingly, the component cooling sea water system pump (A) stopped its 
  operation at 10:07 am on the same day. At 11:25 am on the same day, we 
  confirmed that there was no problem in the operation of the component 
  cooling sea water system pump (C). As a result, two of the component 
  cooling sea water system pumps of Unit 6, (A) and (C), are in operation, 
 
 Others 
- At around 10:00 am on June 13, 2011, we started the operation of the 
  circulating seawater purification facility installed at the screen area 
  of Unit 2 and 3. 
- At 8:00 pm on June 17, 2011, 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, 2011, 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, 2011, 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, 2011, 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, 2011, 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 9:18 am on January 31, we started transfer of Sub-drain Water of Unit 
  6 to the temporary tank. We will conduct transferring to the temporary 
  tank appropriately. 
- At 2:04 pm on February 23, 2012, we started to transfer accumulated 
  water from underground floor of turbine building of Unit 2 to the 
  centralized radiation waste treatment facility. 
- At 9:18 am on January 31, 2012, we started transporting the sub-drain 
  water of Unit 6 to the temporary conservation tank. 
- At 8:21 am on February 24, as the gradual decline in the treated water 
  amount was observed in the second Cesium Adsorption Apparatus, its 
  operation was temporarily suspended to implement the washing of the 
  filter. At 10:30 am on the same day, the operation was restated and 
  designed water flow (approx. 36.0m3/h) was achieved at 10:32 am.