*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. 1.7 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.
The current water injection amount from the reactor feed water system is
approx.7.6m3/h and that from the core spray system is approx.10 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 7:05 am on February 18, within the Unit 2 SFP alternative cooling
system, an alarm sounded showing that the water flow difference was
large at the gateway of primary system pump and the system automatically
shutdown. After that, we confirmed there was no abnormalities such as
leakage at the location where the primary system shutdown. However, as
temperature decreased in the outer temperature, the secondary system
cooing water temperature also decreased and it may freeze, with a view
toward facility protection, we resumed it so as to prevent the primary
and secondary system from freezing. Upon resumption, we made sure there
was no leakage or parameter abnormalities, and by releasing the alarm at
11:54 pm on February 18, we activated the system. Since we do not see
any abnormalities, operation of the system is still continuing.
- 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.
- At around 5:00 am on February 8, the alarm which indicates the
abnormally low suction pressure of the high pressure RO pump in the
desalination apparatus of Unit 2 spent fuel pool went off and the device
was automatically shut down. The interlock closed all the isolation
valves in the system and the alternative cooling system for the spent
fuel pool was activated so there was no interruption to the cooling
process. We also confirmed that there was no leakage from the apparatus.
Due to the investigation afterwards we assumed that an instantaneous
fall in the pressure had caused this shut down. After we confirmed that
certain measures have been taken to prevent this we restarted the
operation at 3:20 pm of February 18, but at 7:05 pm on the same day
another alarm which indicates that the difference of the water flow
between the entrance and the exit of the primary line pump of the
substitutive cooling system of the spent fuel pool of unit 2 went off
and the system shut had down automatically. Due to this the desalting
facility has also shut down, but later we reactivated the system and at
10:44 am on February 19 we restarted the operation of the 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.
- On 9:57 am on February 19, with regard to the water injection volume
for Unit 3 reactor, as there was latitude of the current water injection
volume against the equivalent decay heat, for the purpose of reducing
the transfer and treatment works of the increased accumulated water due
to the increase in water injection to Unit 2, we changed the water
injection volume by feed water system from approx. 3.0 m3/h to 2.0 m3/h.
(The water injection level from reactor core system is continuing at 5.0
m3/h.)
The current water injection amount from the reactor feed water system is
approx. 2 m3/h and that from the core spray system is approx. 5 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.
- 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 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.
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.
- 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]).
- From 10:00 am to 4:00 pm on February 18, we transferred accumulated
water from the turbine building of Unit 6 to the temporary tank.
- At 10:00 am on February 19, as for the accumulated water at the Unit 6
Turbine Building basement, transfer to the temporary tank commenced.
