* 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. 2 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.
Because the tendency of temperature rise at the bottom of PCV had been
accelerated since February 2, we increased the amount of water injected
to the reactor and continued monitoring the tendency of the temperature
fluctuation. Since the temperature had remained high around 70.0 °C, we
injected boric acid into the reactor as a safety countermeasures against
the re-criticality from 0:19 am to 3:20 am on February 7, and changed the
amount of the core spray system injection water from 3.7m3/h to 6.7m3/h
at 4:24 am (the amount of the continuing feed water system injection is
6.8m3/h). Currently, the temperature is approx. 68.0°C (as of 11 am on
February 10). We will monitor the progress continuously.
The current water injection amount from the reactor feed water system is
approx. 6.8 m3/h and that from the core spray system is approx. 6.8 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 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. 3 m3/h and that from the core spray system is approx. 6 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.
Since 9:50 am on February 10, we have conducted the work to add
flowmeters to the nitrogen injection line at the side of Primary
Containment Vessel of Unit 3 in order to improve the reliability of
nitrogen injection activity. During this period, due to this work, we
suspended the nitrogen injection task temporarily (*). At 10:55 am on the
same day, we started operation to inject nitrogen and at 11:24 am, we
complete the series of the operation.
* In the Chapter 12 of Nuclear Reactor Facilities Security Regulation
"The Way of Ensuring Mid-term Security", as the treatments like
"Operational limitation" or "Measures required in case of not
satisfying the operational limitation" are determined, it is supposed
the operator act per the required measures if it fails to satisfy the
operational limitation. This time, to implement maintenance works, we
have suspended the work of nitrogen injection at the side of Primary
Containment Vessel of Unit 3 by conducting a planned shift beyond the
range of operational limitation (from 9:50 am to 11:30 am on February 10).
- 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 1:28 pm on February 10, we started
injection of hydrazine [corrosion inhibitor].
- 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 made on February 9, the location where the
accumulated water was found and the preliminary results of the nuclide
analysis are as follows:
· Inside the duct for telecommunication cables of Unit 5 & 6
I-131: below the detectible limit, Cs-134: below the detectible limit,
Cs-137:7.2x10-2 Bq/ cm3
· Inside the duct for emergency gas treatment piping
I-131: below the detectible limit, Cs-134:4.6x10-1 Bq/ cm3,
Cs-137:6.7x10-1 Bq/ cm3
· Inside the connection duct of Unit 5's chemical tank, inside the trench
for the piping of suppression pool water, inside the duct for common
suppression pool water surge pipe, inside the trench for fire-
extinguishing piping (at the west of Unit 5), inside the trench for
fire-extinguishing piping (at the west of Unit 6), and the inside the
trench of fire-extinguishing piping (at the south of Unit 5), we
confirmed no accumulated water.
- 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]).
- At 10:00 am on February 10, 2012, we started transferring the accumulated
water from the turbine building of Unit 6 to the temporary tank.
- At 8:45 am on February 10, 2012, at the Centralized Radiation Waste
Treatment Facility, we started transferring accumulated water from
On-site Bunker Building to Process Main Building.
- At 8:39 on February 10, 2012, because it has been observed that the
amount of treatment flow of the second Cesium adsorption apparatus
gradually, we suspended temporarily the operation of the apparatus. At
2:19 pm on the same day, we started those instruments, and at 2:32 pm the
rated flow was achieved (approx. 35m3/h).
- At approximately 6:30 pm on February 9, 2012, at Main Anti-Earthquake
Building, we confirmed that data monitoring using temporarily-installed
meters at Unit 1 was disabled. The measurement of plant parameters
including Containment Atmospheric Monitor, Containment vessel pressure,
Drywell HVH temperature, and the water level of the reactor was cancelled.
Later, because it is confirmed that a fuse of the equipment which supply
electricity to the temporarily-installed meters was blown at the central
control center of Unit 1 & 2 and that the power source for the meters was
out of order, at 6:15 am on February 10, we replaced the fuse, resulting
in that the plant parameters excluding Containment Vessel pressure and
the water level of the reactor and the Others were turned to under
monitoring using Unit 1's temporarily-installed meters. Later, after
switching the power from the power source for meters whose fault was
found to the other power source for meters, all the plant parameters
turned to be monitored using the temporarily-installed meters of Unit 1
at 10:55 am on the same day. For reference, while data monitoring using
Unit 1's temporarily-installed meters was disabled, the key parameters in
terms of safety were continued to be monitored using web-cameras and
Others inside the Main Anti-Earthquake Building. Because we confirmed
that there have been no significant fluctuation of the parameters, we
concluded that there is no problem in terms of safety.
