*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.
Current water injection volume is approx. 4.3 m3/h from the reactor feed
water system and approx. 1.8 m3/h from the core spray system.
-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
water feeding system, we started water injection from piping of core
spray system to the reactor.
Current water injection volume is approx. 2.8 m3/h from the reactor feed
water system and approx. 7 m3/h from the core spray system.
-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
management system started.
-At 10:46 am on December 1, 2011, 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, 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.
Current water injection volume is approx 2 m3/h from the reactor feed
water system and approx. 7.1 m3/h from the core spray system.
-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 (from 1:30 pm to 3:14 pm on January 12, 2012,
we injected hydrazine [corrosion inhibitor] in conjunction with the
cyclic cooling).
-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.
-Because of the 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.
-Around 1:40 pm on January 14, extremely small amount of water leakage was
found from 2 pinholes of the hose in water transfer line between the
vertical shaft in Unit 1 to the centralized radiation waste treatment
facility while water passing test was being conducted. The leakage
stopped after suspending the pump. The result of sampling indicated
Iodine 131 was below measurable limit, Cesium 134 was 1.8x101Bq/cm3 and
Cesium 137 was 2.0x101Bq/cm3, We estimate that it is mixture of sea
water and rain water. The pinholes were closed by plastic. The water
leakage point is the outdoor laying part at flushing line that transfer
the accumulated water of the vertical shaft in Unit 1 to the accumulated
water transfer line in Unit 2. The amount of water leakage is estimated
to be less than approximately 1 liter.
