* 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. 4.7 m3/h and that from the core spray system is approx. 1.8 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.
- With regard to the water injection volume for Unit 2 reactor, which was
increased with temperature figure raising, we have gradually adjusted it
to the original volume before temperature increasing (Feed water system:
approx. 3.0m3/h, core spray system: approx. 6.0m3/h).As no abnormality
has been observed in the variation of the plant parameter after the
change in the flow rate on February 20, at 7:44 pm on February 21, we
changed the water injection volume from feed water system from approx.
5.5m3/h to approx. 4.0m3/h (The water injection level from core spray
system is continuing at approx. 6.0m3/h)
The current water injection amount from the reactor feed water system is
approx.4.0m3/h and that from the core spray system is approx.6.0 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 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 around 3:43pm on February 20, we observed that
an error message was displayed in the screen of the noble gas monitoring
system B of the gas management system of the primary containment vessel
of Unit 2. Accordingly, the density of the noble gas in the system B was
no longer observable at the Central Monitoring Station in the Main Anti-
Earthquake Building. Observation was continued using the system A, one of
the two systems A and B, which did not display any error message. However,
at around 5:20pm on February 21, the same error message was displayed in
the screen of system A. As a result, the density of the noble gas was no
longer observable at Central Monitoring Station in the Main Anti-
Earthquake Building. After investigating the situation at the site, we
detected a failure of the transmission system which connects the site and
the Central Monitoring Station in the Main Anti-Earthquake Building.
However, there is no difficulty in confirming the subcriticality, as both
the system A and B can be observed from the monitor at the site and, at
the moment, the monitor screen can be remotely watched from the Central
Monitoring Station in the Main Anti-Earthquake Building. The cause of the
failure is now being investigated for restoration. The gas management
system of the primary containment vessel of Unit 2 itself is in normal
operation.
- 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.
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.
The current water injection amount from the reactor feed water system is
approx. 1.9 m3/h and that from the core spray system is approx. 5.1 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.
- As the component cooling sea water system pump (C) of Unit 6 has been
restored, we started test operation at 10:05 am on February 22.
Accordingly, the component cooling sea water system pump (A) stopped its
operation at 10:07 am on the same day.
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.
- From 9:30 am on February 20 to 9:52 am on February 22, regarding the
accumulated water at the basement of Unit 3 Turbine Building, we
transferred to Centralized Waste Treatment Facility (Miscellaneous Solid
Waste Volume Reduction Treatment Building [High Temperature Incinerator
Building]) .
- At 9:39 am on February 20, regarding the accumulated water at the
basement of Unit 2 Turbine Building, we started transfer to Centralized
Waste Treatment Facility (Miscellaneous Solid Waste Volume Reduction
Treatment Building [High Temperature Incinerator Building]).
- From 9:40 am to 3:45 pm on February 21, at the centralized radiation
waste treatment facility, we transferred accumulated water from site
banker to process main building.
- According to the investigation on trenches on January 19, 2012, high
density contaminated water inside was found inside circulating water pump
discharge valve pit of Unit 2 water pump room. Therefore, from 9:50 am to
3:34 pm on February 21, we transferred the accumulated water from the pit
to the basement of Unit 2 Turbine Building. At 9:43 am on February 22, we
restarted the transfer.
- From 10:00 am to 4:00 pm on February 21, we transferred accumulated water
from underground floor of turbine building of Unit 6 to temporary tank.
