* Updates from previous press release 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. 4.7 m3/h and that from the core spray system is approx. 1.6 m3/h.
- At 1:31 am on April 7, 2011, we commenced injection of nitrogen gas into 
  Primary Containment Vessel.
- 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. 
- 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. 
  The current water injection amount from the reactor feed water system is 
  approx. 2.7 m3/h and that from the core spray system is approx. 6 m3/h.
- 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 12:21 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. Through the investigation, we confirmed the 
  concerned device is soundness. We submitted the report on the soundness 
  of concerned device and the alternative method for monitoring temperature 
  inside the Reactor of Unit 2 at Fukushima Daiichi Nuclear Power Station 
  to NISA on March 1. We continue the observation of the concerned device.
  · At 5:00 am on March 14, the temperature of the lower part of the RPV 
    (top of the lower head 135°) : approximately 39.5 °C 
  · At 5:00 am on March 14, the temperature of the lower part of the RPV 
    (top of the lower head 270°) : approximately 40.6 °C (Reference)
- 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.
- At 10:31 am on March 13,2012, because the suction pressure of the primary 
  system Circulating Water Pump had a tendency to decrease in the 
  substitute cooling system of spent fuel pool, we stopped the cooling of 
  spent fuel pool in order to change the primary system Strainer to manual 
  cleaning system and conduct the check of valves etc. until March 16. The 
  temperature rise on this period is expected approx. 21 °C. (Temperature 
  of water in spent fuel pool when we stopped: approx. 14.1 °C)
 
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. 
  The current water injection amount from the reactor feed water system is 
  approx. 1.8 m3/h and that from the core spray system is approx. 5.3m3/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.
 
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 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.
 
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.
 
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 8:47 am on March 11, we started transferring the accumulated water 
  from the basement of Turbine Building of Unit 2 to the centralized 
  radiation waste treatment facility (Miscellaneous Solid Waste Volume 
  Reduction Treatment Building [High Temperature Incinerator Building]).
- At 10:10 am on March 10, 2012, we started transferring the accumulated 
  water from the basement floor of the turbine building of Unit 3 to the 
  centralized radiation waste treatment facility (Miscellaneous Solid Waste 
  Volume Reduction Treatment Building [High Temperature Incinerator 
  Building]). At 9:53 am on March 13, 2012, we stopped transferring.
- From 10:00 am to 4:00 pm on March 13, we transferred accumulated water on 
  the basement of Turbine Building of Unit 6 to the temporary tank. 
- At 10:00 am on March 14, we started transferring accumulated water on the 
  basement of Turbine Building of Unit 6 to the temporary tank. 
- In order to stop the offset power and change the station power supply 
  with starting to operate the south switching station, we stopped the 
  operation of desalination facility (reverse osmosis membrane type) at 
  4:25 am on March 13, 2012,and the cesium adsorption instrument No.2 at 
  5:43 am on the same day. Since we finished changing the station power 
  supply, we resumed the operation of desalination facility (reverse 
  osmosis membrane type) at 12:23 pm on the same day, and we resumed the 
  operation of cesium adsorption instrument No.2 at 12:39 pm on the same 
  day.
- At 8:09 am on March 14, in order to investigate soundness of the transfer 
  line from Centralized Radiation Waste Treatment Facility (Process Main 
  Building) to cesium absorption instrument No.2, that was newly settled to 
  enhance security in the water treatment system, cesium absorption 
  instrument No.2 was suspended.