* 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.
  1.7 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. 3.0 m3/h, core spray system: approx. 6.0 m3/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 15, the temperature of the lower part of the RPV 
   (top of the lower head 135°) : approximately 40.6 °C 
  · At 5:00 am on March 14, the temperature of the lower part of the RPV 
   (top of the lower head 270°) : approximately 40.8 °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. 1.7 m3/h and that from the core spray system is approx.
  5.4 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.
- At 4:26 pm on November 30, 2011, we started operation to inject
  nitrogen into the reactor pressure vessel.
- 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. As the result of the adjustment 
  operation, we confirmed no significant problem with the gas control 
  system. Therefore, the regular operation started of the system started 
  at 7:00 pm on March 14. 
 
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 8:46 am on March 15, 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]). 
- From 10:00 am to 4:00 pm on March 14, we transferred accumulated water
  on the basement of Turbine Building of Unit 6 to the temporary tank. At 
  10:00 am on March 15 in the same year, we started the transfer. 
- At 8:09 am on March 14, 2012, 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. After its trial run, no 
  significant problem with the instrument was confirmed. Therefore the 
  transfer line was switched and the instrument was started at 7:32 pm on 
  the same day. The treatment of the accumulated water at the process 
  main building of Centralized Radiation Waste Treatment Facility 
  (Miscellaneous Solid Waste Volume Reduction Treatment Building "High 
  Temperature Incinerator Building") was restarted. At 7:39 pm, the 
  constant flow status was attained (approximately 42 m3/h). 
- Accumulated water (volume: about 220 m3) in the trench located between
  the process main building of Centralized Radiation Waste Treatment
  Facility and Miscellaneous Solid Waste Volume Reduction Treatment
  Building (High Temperature Incinerator Building) found on December 18,
  2011 was transferred to Miscellaneous Solid Waste Volume Reduction
  Treatment Building (High Temperature Incinerator Building) on December
  23 in the same year (transfer volume: about 120 m3). Since then, the 
  water level has been monitored. Because the water level has been rising, 
  the accumulated water was started to be transferred to Miscellaneous 
  Solid Waste Volume Reduction Treatment Building (High Temperature 
  Incinerator Building) at 3:35 pm on March 14, 2012. The transfer was 
  stopped at 8:20 am on March 15, 2012 (transfer volume: about 120 m3).