* 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. 2 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. 
  To improve reliability of water injection to the reactors, the injection 
  line connecting to the reactor injection pump on the hill was replaced 
  with polyethylene pipes and we have been changing the route for reactor 
  injection from feed water system to reactor core spray system in a 
  stepwise manner. After completion of adjusting water flow amount as 
  planned on February 2, tendency of temperature rise at the bottom of PCV 
  was observed. Thus, at 7:20 pm on February 3, 2012, we changed the 
  injection amount into Unit 2 reactor through feed water system from 
  approx. 2.9 m3/h to approx. 4.9 m3/h and changed that though reactor 
  core spray system from approx. 5.8 m3/h to approx. 3.8 m3/h (which means 
  setting them at those of before flow adjustment on February 1, 2012). 
  After that, we have observed the tendency of temperature at the upper 
  head of the bottom of PCV. The temperature was around 70.0 °C (approx. 
  70.3 °C at 11:00 pm on February 5) and in order to prevent further 
  temperature increase, we decided to increase the amount of water 
  injected to the reactor. At 1:29 pm on February 6, the water injection 
  volume to the Unit 2 reactor through the feed water system was changed 
  from approx. 5.8 m3/h to approx. 6.8 m3/h (the water injection through 
  the reactor core spray system remains approx. 3.8 m3/h). At this moment, 
  temperature indicates approx. 71.0 °C (as of 11:00 am on February 6). As 
  a result of the sampling for the Gas Control System of the Unit 2 which 
  we conducted on the same day to make sure there is no re-criticality 
  state, we confirmed that the concentration of Xe-135 was below the 
  detectible limit (1.0 x 10-1 Bq/ cm3) at the system's entrance, meaning 
  that it falls below the re-criticality criteria, or 1 Bq/cm3. Continuing 
  to monitor the trend after that, as it was still showing a high value, 
  from 0:19 am to 3:20 am on February 7 we injected boric acid into the 
  reactor as a safety countermeasures against the re-criticality, and at 
  4:24 pm we changed the amount of the core spray system injection water 
  from 3.7m3/h to 6.7m3/h* (the amount of the continuing feed water system 
  injection is 6.8m3/h). Currently, the temperature is 72.2°C (as of 5 am 
  on February 7). We will monitor the progress continuously.  
  The current water injection amount from the reactor feed water system is 
  approx. 6.7 m3/h and that from the core spray system is approx. 6.7 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-scale 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. 2.9 m3/h and that from the core spray system is approx. 5.8m3/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.
- 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 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 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.
- At this moment, we do not think there is any reactor coolant leakage 
  inside PCV. 

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.
- As finding of accumulated water containing radioactive materials at the 
  trench between the Process Main Building and the Miscellaneous Solid 
  Waste Volume Reduction Treatment Building [High Temperature Incinerator 
  Building] (December 18, 2011), we started the inspection of other 
  trenches at the site on January 11.
  As a result of the inspection made on February 6, the preliminary 
  results of the nuclide analysis and executed place are as follows:  
  · Inside the Unit 6 off-gas plumbing duct 
    I-131: below the detectible limit, Cs-134: 1.2 x 10-1 Bq/ cm3, 
    Cs-137: 1.9 x 10-1 Bq/ cm3  
  · Inside the Unit 5 pump room circulating water pump valve disorption 
    pit 
    I-131: below the detectible limit, Cs-134: 1.0 x 10-1 Bq/ cm3, 
    Cs-137: 1.6 x 10-1 Bq/ cm3 
  · Inside the Unit 6 pump room circulating water pump valve disorption 
    pit 
    I-131: below the detectible limit, Cs-134: 1.1 x 10-1 Bq/ cm3, 
    Cs-137: 1.4 x 10-1 Bq/ cm3 
  · Inside the Unit 5 off-gas duct and heavy oil plumbing trench (the 
    southwest side of Unit 5), we confirmed there is no puddle water 
- 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 9:49 am on February 5, we started water transfer from the basement of 
  turbine building of Unit 3 to Centralized Radiation Waste Treatment 
  Facility (Miscellaneous Solid Waste Volume Reduction Treatment Building 
  [High Temperature Incinerator Building]).
- From 10:00 am to 16:00 pm on February 6, we transferred water from the 
  basement of turbine building of Unit 6 to the temporary tank.
- At 12:28 pm on February 6, 2012, at a group of concentrated water 
  storage tanks, a TEPCO employee found a leakage from on the tanks. As a 
  result of tightening a connecting volt of the tank, at 2:03 pm on the 
  same day, we confirmed stoppage of the leakage's bleed at the connecting 
  part. The leaked water originated from the concentrated water (salt 
  water) after being treated by the desalination equipment (reverse 
  osmosis membrane) and we evaluated a leakage amount of 0.6L. Currently, 
  as there still remains the bleed coming down from the connecting part on 
  the surface of the cement on which the tank is installed, we don't find 
  any water flowing into the gutter, and thus it will not flow out into 
  the ocean. (At 2:45 pm on the same day, we have piled sandbags just in 
  case). In the mean time, as a result of measuring the surface 
  radioactive rate at the cement basement right under the connecting part 
  that has the bleed, Gamma ray was 20mSv/h and Beta ray 250mSv/h. 
 
* 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 changed the
amount of water injection into Unit 2 (from 3:48 am on February 7) by
conducting a planned shift beyond the range of operational limitation.