*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 10:35 am on December 2, we adjusted water injection volume from 
 approx. 4.0m3/h to approx. 4.5m3/h since decrease in injection volume was 
 observed. 
 The current water injection volume is approx 4.5m3/h from the reactor
 feed water 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. 
 
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, we started injecting water to the reactor
 through core spray system water injection piping arrangement in addition
 to the water injection through reactor feed water system piping
 arrangement.
 Water is currently injected at approx. 3.1m3/h through reactor feed water
 system piping arrangement, and at approx. 4.3 m3/h through core spray
 system water injection piping arrangement.
-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 11:13 on November 30, the alarm went off at the alternative cooling
 system in the Fuel Pool Cooling and Filtering System indicating that the
 difference of the flow rate between at the inlet and at the outlet is
 large and the system automatically stopped its operation. On December 2, 
 it was estimated that air or foreign materials entered the detection 
 line. We conducted flushing and fulfilled it with clean water and 
 restarted cooling the spent fuel pool at 1:50pm on the same day. (As at 
 restart temperature of water was 28.0°C.) 
-At 8:06 pm on June 28, we started injecting nitrogen gas into the Primary
 Containment Vessel.
-From 6:00 pm on October 28, we put the gas management system of the
 reactor containment vessel in operation.
-At 11:04 am on November 6, we started operation of radioactive material
 decontamination instrument of spent fuel pool.
-At 10:46 am on December 1, we started the nitrogen injection to the
 Reactor Pressure Vessel.
 At 10:25 am on December 2, we adjusted the volume of nitrogen injected 
 into the Reactor Pressure Vessel from approx. 5Nm3/h to approx. 10Nm3/h. 
 In addition, in order to balance the volume of nitrogen injected into the 
 Reactor Pressure Vessel and the Primary Containment Vessel of Unit 2 and 
 the volume of exhaust air from gas control system, we adjusted the volume 
 of exhaust air from gas control system of the Primary Containment Vessel 
 from approx. 34Nm3/h to approx. 39Nm3/h. 
 
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. 
 Water is currently injected at approx. 2.1 m3/h through reactor feed
 water system piping arrangement, and at approx. 6.1 m3/h through core
 spray system water injection piping arrangement.
-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.
-At 9:01 am on December 2, we interrupted the operation of the alternative
 cooling in order to replace the inside mesh of the primary strainer as a
 countermeasure against the decrease in inhale pressure of the primary
 pump for alternative cooling of the spent fuel pool. The temperature of
 the spent fuel pool as at the interruption was 18°C and expected
 temperature increase was 0.2°C/h (duration of interruption: approx.
 3hours). The water temperature of the spent fuel pool is in a normal
 state.  
 
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.
-Regarding spent fuel pool for unit 4, from August 20 to November 8, we
 had decreased salinity by using the desalting facility. In order to
 decrease more salinity, we installed Ion exchange equipment and started
 the equipment at 10:58 am on November 29.
-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 2:30 pm on March 20, the reactor achieved cold shutdown.
-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.
-From November 28, we started cleaning to avoid the performance
 deterioration of pumps by sucking up sands etc. accumulated at the bottom
 of the inlet canal pump room.
-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 7:27 pm on March 20, the reactor achieved cold shutdown. 
-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 9:25 am on November 15, we started transfer of accumulated water from
 basement of Unit 3 turbine building to Centralized Radiation Waste
 Treatment Facility Building.
-At 6:03 pm on November 30, we started transfer of the accumulated water
 from the basement of Unit 2 turbine building to Centralized Radiation
 Waste Treatment Facility High Temperature Incinerator Building.
-At 10:00 am on December 1, we started transfer of the accumulated water
 from Unit 6 turbine building to Temporary Tank.
-From 10:10 am to 12 pm on December 2, we conducted dust sampling at the 
 ventilation equipment filter of Unit 1 reactor building cover. 
-From 1 pm to 2 pm on December 2, we conducted dust sampling and measured 
 air flow at the upper part of the reactor building equipment hatch of 
 Unit 1. 
-From 12 pm to 2 pm on December 2, we conducted dust sampling at the 
 opening of Unit 2 reactor building (blow-out panel). 
-On December 2, we conducted sampling at charcoal filter and particulate 
 filter of gas control system of Unit 2 Primary Containment Vessel. 
-From 11 am to 1 pm on December 2, we confirmed leakage at 7 points in the 
 hose which was used for the water transfer from the desalination facility 
 to the buffer tank (the leakage was at one or two drops per second.). 
 Then we made a tentative repair with water stopping tape and confirmed 
 that the leakage stopped. Since the leaked water was one treated through 
 decontamination and desalination process and the leaked amount was so 
 little, there will be no impact on the environment.