* 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. 4.4 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. 
- 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. 
  At 6:20 pm on March 2, 2012, since the flow rate of the water injected 
  to the reactor was dropped, we adjusted the water injection amount from 
  the reactor feed water system from approx. 2.6 m3/h to approx. 3 m3/h 
  and that from the core spray system from approx. 5.7 m3/h to approx. 6 m3/h. 
  The current water injection amount from the reactor feed water system is 
  approx. 3 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 3, the temperature of the lower part of the RPV 
   (top of the lower head 135°) : approximate 44.9 °C 
  ·At 5:00 am on March 3, the temperature of the lower part of the RPV 
   (top of the lower head 270°) : approximate 41.7 °C (Reference) 
   Since the temperature measured by a RPV thermometer (at the upper part 
   of RPV supporting skirt junction 270°) was increasing, we surveyed the 
   thermometer during 11:08 am to 11:23 am on March 2, 2012, and found the 
   DC resistance increasing. In order to check the reliability of it, we 
   examined the trend of the temperature. As a result, at 11:00 pm on the 
   same day, we decided to exclude it from the monitoring meters 
   stipulated by the Safety Regulations, and to keep monitoring the valued 
   it shows as a reference. The reactor is kept being cooled, and the 
   concentration of Xenon 135 measured by the noble gas monitor of PCV gas 
   control system was below the detection limit, meaning that the 
   concentration is below 1 Bq/cm3, which is the threshold of re-critical 
   condition. Therefore, we consider it hasn't gone re-critical. We will 
   keep monitoring the temperature at the bottom of PCV using other 
   devices. 
- 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. 
  The current water injection amount from the reactor feed water system is 
  approx. 1.5 m3/h and that from the core spray system is approx. 5.2m3/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. 
  On March 1, 2012, we took samples on the gas in PCV gas control system 
  under the test operation. We confirmed based on the result of the 
  analyses that the concentration of Xenon 135 at the inlet of the system 
  was below the detection limit, meaning that it is below 1 Bq/cm3, which 
  is the threshold of re-critical condition. 
- 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 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 1:56 pm on February 28, we started transfer the accumulated water 
  from the basement of turbine building of Unit 3 to Miscellaneous Solid 
  Waste Volume Reduction Treatment Building (High Temperature Incinerator 
  Building). 
- At 2:00 pm on February 28, we started transferring accumulated water 
  from basement of unit 2 turbine building to Centralized Radiation Waste 
  Treatment Facility Process Main building. 
- At 9:44 am on March 2, in order to conduct the work to switch the 
  control circuits of on-site power source for operation of southern 
  switching station, we cut the power of on-site power source. The 
  evaporation apparatuses of water desalination facilities and 
  desalination facilities (reverse osmosis membrane type) are out of 
  service due to the work to switch the control circuits. We also have 
  sufficient volume of treated water, therefore there will be no impact on 
  the water injection to the reactors. 
- At 9:43 am on March 3, 2012, we started transferring the water 
  accumulated in the site banker building to the process main building in 
  the centralized waste treatment facilities.