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Press Release (Feb 10,2012)
Plant Status of Fukushima Daiichi Nuclear Power Station (as of 3:00 pm, February 10)
* 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. 
  Because the tendency of temperature rise at the bottom of PCV had been 
  accelerated since February 2, we increased the amount of water injected 
  to the reactor and continued monitoring the tendency of the temperature 
  fluctuation. Since the temperature had remained high around 70.0 °C, we 
  injected boric acid into the reactor as a safety countermeasures against 
  the re-criticality from 0:19 am to 3:20 am on February 7, and changed the 
  amount of the core spray system injection water from 3.7m3/h to 6.7m3/h 
  at 4:24 am (the amount of the continuing feed water system injection is 
  6.8m3/h). Currently, the temperature is approx. 68.0°C (as of 11 am on 
  February 10). We will monitor the progress continuously.
  The current water injection amount from the reactor feed water system is 
  approx. 6.8 m3/h and that from the core spray system is approx. 6.8 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. 3 m3/h and that from the core spray system is approx. 6 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. 
  Since 9:50 am on February 10, we have conducted the work to add 
  flowmeters to the nitrogen injection line at the side of Primary 
  Containment Vessel of Unit 3 in order to improve the reliability of 
  nitrogen injection activity. During this period, due to this work, we 
  suspended the nitrogen injection task temporarily (*). At 10:55 am on the 
  same day, we started operation to inject nitrogen and at 11:24 am, we 
  complete the series of the operation. 
  * 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 
    have suspended the work of nitrogen injection at the side of Primary 
    Containment Vessel of Unit 3 by conducting a planned shift beyond the 
    range of operational limitation (from 9:50 am to 11:30 am on February 10).
- 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 1:28 pm on February 10, we started 
  injection of hydrazine [corrosion inhibitor]. 
- 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 9, the location where the 
  accumulated water was found and the preliminary results of the nuclide 
  analysis are as follows:
  · Inside the duct for telecommunication cables of Unit 5 & 6
    I-131: below the detectible limit, Cs-134: below the detectible limit, 
    Cs-137:7.2x10-2 Bq/ cm3 
  · Inside the duct for emergency gas treatment piping
    I-131: below the detectible limit, Cs-134:4.6x10-1 Bq/ cm3, 
    Cs-137:6.7x10-1 Bq/ cm3 
  · Inside the connection duct of Unit 5's chemical tank, inside the trench 
    for the piping of suppression pool water, inside the duct for common 
    suppression pool water surge pipe, inside the trench for fire-
    extinguishing piping (at the west of Unit 5), inside the trench for 
    fire-extinguishing piping (at the west of Unit 6), and the inside the 
    trench of fire-extinguishing piping (at the south of Unit 5), we 
    confirmed no accumulated 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 2:43 pm on February 10, we started to transfer accumulated water from 
  underground floor of turbine building of Unit 2 to centralized radiation 
  waste treatment facility (Miscellaneous Solid Waste Volume Reduction 
  Treatment Building [High Temperature Incinerator Building]). 
- At 10:00 am on February 10, 2012, we started transferring the accumulated 
  water from the turbine building of Unit 6 to the temporary tank.
- At 8:45 am on February 10, 2012, at the Centralized Radiation Waste 
  Treatment Facility, we started transferring accumulated water from 
  On-site Bunker Building to Process Main Building.
- At 8:39 on February 10, 2012, because it has been observed that the 
  amount of treatment flow of the second Cesium adsorption apparatus 
  gradually, we suspended temporarily the operation of the apparatus. At 
  2:19 pm on the same day, we started those instruments, and at 2:32 pm the 
  rated flow was achieved (approx. 35m3/h). 
- At approximately 6:30 pm on February 9, 2012, at Main Anti-Earthquake 
  Building, we confirmed that data monitoring using temporarily-installed 
  meters at Unit 1 was disabled. The measurement of plant parameters 
  including Containment Atmospheric Monitor, Containment vessel pressure, 
  Drywell HVH temperature, and the water level of the reactor was cancelled. 
  Later, because it is confirmed that a fuse of the equipment which supply 
  electricity to the temporarily-installed meters was blown at the central 
  control center of Unit 1 & 2 and that the power source for the meters was 
  out of order, at 6:15 am on February 10, we replaced the fuse, resulting 
  in that the plant parameters excluding Containment Vessel pressure and 
  the water level of the reactor and the Others were turned to under 
  monitoring using Unit 1's temporarily-installed meters. Later, after 
  switching the power from the power source for meters whose fault was 
  found to the other power source for meters, all the plant parameters 
  turned to be monitored using the temporarily-installed meters of Unit 1 
  at 10:55 am on the same day. For reference, while data monitoring using 
  Unit 1's temporarily-installed meters was disabled, the key parameters in 
  terms of safety were continued to be monitored using web-cameras and 
  Others inside the Main Anti-Earthquake Building. Because we confirmed 
  that there have been no significant fluctuation of the parameters, we 
  concluded that there is no problem in terms of safety. 
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