*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. It was assumed to be hydrogen explosion.
-At 3:37 pm on March 25, 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, 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 volume is approx. 4.3 m3/h from the reactor
 feed water system and approx. 2 m3/h from the core spray system.
-We commenced injection of nitrogen gas into Primary Containment Vessel at
 1:31 am on April 7.
-At 11:22 am on August 10, 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, 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, we started operation to inject nitrogen into
 the reactor pressure vessel.
-At 6:00 pm on December 19, a full-scale operation of the PCV gas control
 system started.

Unit 2 (Shut down) 
-At approximately 6:00 am on March 15, an abnormal noise began emanating
 from nearby Pressure Suppression Chamber and the pressure within the
 chamber decreased. 
-At 10:10 am on March 26, 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, 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 volume is approx. 2.9 m3/h from the reactor
 feed water system and approx. 6 m3/h from the core spray system.
-At 5:21 pm on May 31, 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, we started injecting nitrogen gas into the Primary
 Containment Vessel.
-At 6:00 pm on October 28, we put the gas management system of the reactor
 containment vessel in operation.
-At 10:46 am on December 1, we started the nitrogen injection to the
 Reactor Pressure Vessel.

Unit 3 (Shut down) 
-Explosive sound and white smoke were confirmed at approximately 11:01 am
 on March 14. It was assumed to be hydrogen explosion.
-At 6:02 pm on March 25, 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, 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 volume is approx 3 m3/h from the reactor feed
 water system and approx. 6 m3/h from the core spray system.
-At 7:47 pm on June 30, 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, injection of nitrogen gas into the Primary
 Containment Vessel started. 
-At 4:26 pm on November 30, 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, 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, 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, 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, we started the Residual Heat Removal System Pump
 in order to cool the spent fuel pool.
-At 2:45 pm on July 15, 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, 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, we started the Residual Heat Removal System Pump
 of Unit 6 to cool down Spent Fuel Pool.
-At 2:33 pm on September 15, 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 am on June 13, we started the operation of the circulating
 seawater purification facility installed at the screen area of Unit 2 and
 3.
-At 8 pm on June 17, 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, 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, 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, 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, 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 1:57 pm on December 21 to 9:42 am on December 23, transfer of
 accumulated water was implemented from Unit 2 turbine building to the
 Centralized Radiation Waste Treatment Facility (Miscellaneous Solid Waste
 Volume Reduction Treatment Building [High Temperature Incinerator
 Building] and Process Main Building).
-At 10:00 am on December 18, during the patrol activity, a TEPCO employee
 found accumulated water 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). The depth of the water was estimated
 to be 50 cm and the amount was to be 125 m3. The radiation dose at the
 water surface was 3 mSv/h (provisional value). As no radioactive
 materials have been detected during the last sampling survey of sub drain
 water near the trench, the source of the accumulated water is estimated
 to be the ground water or dew condensation water. 
 After that we found water inflow from cable duct near the ceiling of the 
 trench by detailed survey at site, and we recalculated the amount of the 
 accumulated water and it was estimated to be approx. 230 m3. And as a 
 result of the sampling, Cesium-134 was approx. 4.2 x 103 Bq/cm3, 
 Cesium-137 was approx. 5.4 x 103 Bq/cm3 and Iodine-131 was below 
 detection limit regarding the radioactivity density of the accumulated 
 water in the trench, and Cesium-134 was approx. 1.3 x 10-1 Bq/cm3, 
 Cesium-137 was approx. 1.2 x 10-1 Bq/cm3 and Iodine-131 was below 
 detection limit regarding the inflowing water from cable duct. We have 
 conducted water shut-off treatment of the trench and the groundwater 
 level is higher than the water level in the trench, therefore we assumed 
 that there is no possibility of inflow of the accumulated water in the 
 trench to the groundwater. 
 Accumulated water 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 was started to transfer to Miscellaneous
 Solid Waste Volume Reduction Treatment Building (High Temperature
 Incinerator Building) from 10:19 am on December 23, and we stopped the
 transfer at 8:13 pm on the same day, as the planned transfer was finished
 (the transferred amount was approx: 120 m3). Regarding the amount of the
 accumulated water, we had estimated it at approx: 230 m3 based on the
 rough shape of the trench, however, after checking the shape particularly,
 we changed the estimation to approx: 220 m3. The remaining water after
 the transfer is approx. 100 m3. We will consider ways of transferring the
 remained water hereafter.
-At 4:07 pm on December 23, we started transfer of accumulated water from
 basement floor of the Turbine Building of Unit 1 to the basement floor of
 the Turbine Building of Unit 2.
-At 2:35 pm on December 24, we started transfer of accumulated water from 
 basement floor of the Turbine Building of Unit 3 to the Centralized 
 Radiation Waste Treatment Facility (the Miscellaneous Solid Waste Volume 
 Reduction Treatment Building［High Temperature Incinerator Building］and 
 the Process Main Building).