*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.
Since fluctuation of the water injection rate was confirmed at 9:53 am
on January 18, 2012, we adjusted injection rate from feeding piping from
approx. 4.8m3/h to approx. 4.5 m3/h, and injection rate from core spray
water injecting piping from approx. 1.8 m3/h to approx. 2 m3/h.
The Current water injection volume is approx. 4.5 m3/h from the reactor
feed water system and approx. 2.0 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.
Since fluctuation of the water injection rate was confirmed at 9:53 am
on January 18, 2012, we adjusted injection rate from feeding piping from
approx. 2.4m3/h to approx. 3.0 m3/h, and injection rate from core spray
water injecting piping from approx. 7.5 m3/h to approx. 7.0 m3/h.
The Current water injection volume is approx. 3.0 m3/h from the reactor
feed water system and approx. 7.0 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.
- At 9:43 am on January 18, 2012, in conjunction with switching injection
piping of reactor injection pump on the hill, we adjusted the amount of
the water injection from approx. 1.9 m3/h to approx. 3.0 m3/h through
the reactor feed water system, from approx. 7.5 m3/h to approx. 6.0 m3/h
through the core spray system.
The Current water injection volume is approx 3 m3/h from the reactor
feed water system and approx. 6.0 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.
- 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 of January 17, the locations where
accumulated water was discovered and the nuclide analysis results
(preliminary results) are as follows:
- Unit 4 Chemical tank joint duct
I-131:Not detected, Cs-134:1.3 x 100Bq/cm3,Cs-137:1.7 x 100Bq/cm3
- Unit1 Spare power resources cable duct
I-131:Not detected, Cs-134:5.4 x 10-1Bq/cm3,Cs-137:8.0 x 10-1Bq/cm3
- We confirmed that no accumulated water in the Unit 3 Chemical tank
joint duct and Unit 2 radioactive fluid piping.
- At around 4:10 pm on January 17, 2012, due to defect of switching gear
at Minami-Iwaki switching station, Yonomori line 1 and 2 were
instantaneously shut down. Facilities which were shut down due to the
effect of this are described below. We confirmed there is no problem
on the facilities which were shut down and sequentially re-started on
the same day. Also there is no big change on major parameter by this
shut down.
- Nitrogen inclusion facility of Unit 1 to 3 [activated on 4:57 pm]
- Alternative cooling system for spent fuel pool of Unit 2 [Activated on
4:53 pm]
- Alternative cooling system for spent fuel pool of Unit 3 [Activated on
5:15 pm]
- Cooling and filtering system for spent fuel pool of Unit 6 [Activated
on 5:19 pm]
- Gas control system of Primary Containment Vessel of Unit 2 [Activated
on 5:25 pm]
- Cesium adsorption apparatus [Activated on 6:42 pm, reached steady flow
rate on 6:45 pm]
- Radioactive material removal system of spent fuel pool of Unit 3
[Activated on 7:04 pm]- At 3:00 pm on January 18, 2012, the instrument to measure the
concentration of radioactive materials in air continuously (continuous
dust monitor), which is located in front of Main Anti-Earthquake
Building, issue an alert. Following the alert, based on the operation
rule of full-face mask wearing, we instructed to wear the full-face
masks from 3:11 pm on the same day.
Later, we confirmed that there was no valid fluctuation on the value
shown by the monitoring post. We replaced the filters of the measurement
instrument, and rebooted the instrument by resetting at 3:40 pm on the
same day. According to the result of manual measurement of radioactive
materials in air in front of Main Anti-Earthquake Building, the
concentration of radioactive materials in air at Main Anti-Earthquake
Building was less than the detection level (the detection limit: 1.4 x
10-5[Bq/cm3] and the value was less than the standard level to wear
full-face masks (1 x 10-4[Bq/cm3]). Therefore, we announced to resume
the normal operation which does not require to wear full-face masks.
