* 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. 4.8 m3/h and that from the core spray system is approx. 1.8 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.
- Around 10:00 am on March 11, 2012: TEPCO's employees found the water 
  leaks from the ceiling near the wall of the west side in the heater room 
  at 1st floor of T/B of Unit 1 when they went there to conduct the 
  sampling works for the accumulated water. The puddle of water at the 
  floor is approx. 5m x 7m and we found the water flow into near funnel*. 
  As the result of the inspection, the water came from the damaged part of 
  the pipe," we assumed the roof drain pipe", which was set at the upper 
  of the ceiling and we assumed that the water was rain or melted snow. 
  The radiodensity of the water was Cs-134:1.1x101Bq/cm3 and Cs-137: 
  1.7x101Bq/cm3. The leakage water was staying in the underground of T/B 
  as the accumulated water and it is considered that there was no leakage 
  to the ocean. 
  *water inlet which gather the water and lead the water from the pipe or 
   facilities in the building to the drain tank 
 
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. 2.9 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 11:00 am on March 11, the temperature of the lower part of the RPV 
   (top of the lower head 135°) : approximately 41.2 °C 
  ·At 11:00 am on March 11, the temperature of the lower part of the RPV 
   (top of the lower head 270°) : approximately 40.1 °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. 
 
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. 5.1m3/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.
- From 1:55 pm on March 7, 2012 to 8:30 am on March 11, we transferred the
  accumulated water from the underground of Unit 2 turbine building to the
  centralized radiation waste treatment facility process main building.
- 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 of 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]).
- In order to conduct the work to improve the reliability of water
  treatment facilities, we are planning to stop water treatment facilities
  one after another. At 8:45 am on March 1, we stopped the cesium
  adsorption apparatus. It will be out of service until March 15. We
  calculated the estimated water level increase at each building due to
  the stop o the facilities, and confirmed that the water levels in each
  building will be maintained within the limits. We also have sufficient
  volume of treated water therefore there will be no impact on the water
  injection to the reactors. At 8:07 am on March 2, we stopped the 2nd
  cesium adsorption apparatus. At 5:00 pm on March 10, we started the 2nd
  cesium adsorption apparatus after the improvement works. At 6:34 pm on
  March 10, the water injection volume reached at normal level (approx.
  42 m3/h).