* 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. 4.4 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.
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 3.7 m3/h
to 6.7 m3/h at 4:24 am (the amount of the continuing feed water system
injection is 6.8 m3/h). Currently, the temperature is approx. 66.8°C (as
of 11 am on February 9). We will monitor the progress continuously.
At 9:47 am February 9, as the amount of water injection decrease, we
adjusted the volume from the feed water system of reactor Unit 2
increased from approx. 6.4 m3/h to approx. 6.8 m3/h(the amount of the
continuing injection from reactor core spray system is approx. 6.8 m3/h.
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. From 10:21 am to 12:35 pm on February 9, for
the reliability improvement of nitrogen injection, we are working for
installing additional flow meter to the nitrogen injection line of the
Primary Containment Vessel (PCV) of Unit 2. Although we suspended the
injection temporarily, there is no significant change of the parameter.
- 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.
* 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
suspended the nitrogen injection into the PCV of Unit 2 (from 10:21 am
on February 9 to 12:35 pm on February 9) by conducting a planned shift
beyond the range of operational limitation.
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. 2.8 m3/h and that from the core spray system is approx.
5.8 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.
- With the regular inspection of the residual heat removal system (RHR)
at 10:14 on February 9, we stopped the RHR. At 2:02 pm, we rebooted the
system and restarted the reactor cooling. Due to the suspension, the
reactor's water temperature increased from 27.5°C to 30.6°C temporarily,
but in terms of the increase level of reactor water temperature, we
estimated it no problem.
- 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 8, the preliminary
results of the nuclide analysis and executed place are as follows:
· Inside the duct for power cables for the Unit 6 water intake
I-131: below the detectible limit, Cs-134: 1.0×10-1 Bq/cm3,
Cs-137: 8.3×10-2 Bq/cm3
· Inside the trench for the Unit 5 and 6 storm drain pipes
I-131: below the detectible limit, Cs-134: 1.7×10-1 Bq/cm3,
Cs-137: 2.5×10-1 Bq/cm3
· Inside the duct for the Unit 5 radioactive fluid pipes
I-131: below the detectible limit, Cs-134: 8.0×10-2 Bq/cm3,
Cs-137: 1.3×10-1 Bq/cm3
· Inside the duct for the Unit 6 main transformer cables
I-131: below the detectible limit, Cs-134: 2.8×10-1 Bq/cm3,
Cs-137: 4.3×10-1 Bq/cm3
· Inside the trench for heavy oil pipes (east of Unit 5)
I-131: below the detectible limit, Cs-134: 2.0×10-1 Bq/cm3,
Cs-137: 2.8×10-1 Bq/cm3
- 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 2:14 pm on February 7, 2012, we started transferring the accumulated
water from the basement of turbine building of Unit 2 to Centralized
Radiation Waste Treatment Facility (Miscellaneous Solid Waste Volume
Reduction Treatment Building [High Temperature Incinerator Building]).
- From At 10:00 am to 4:00 pm on February 8, 2012, we transferred the
accumulated water from inside the turbine building of Unit 6 to the
temporary tank.
- At 10:00 am on February 9, 2012, we started transferring the
accumulated water from the turbine building of Unit 6 to the temporary
tank.
- At 7:10 on February 9, a partner company's worker found that one end of
a silt fence of Unit 1 screen came off. The silt fences were installed
both inside and outside of the screen, and the one which came off was
the inside. At 10:30 am we refitted it. We implemented sampling survey
of both silt fences everyday and there was no significant change from
today's sample which we took before the incident.
- The newly found water leakage caused by frost after the previous report
(at 3:00 pm on February 3) is as follow:
Secondary cooling system air fin cooler of the spent fuel pool
alternative cooling system of Unit 4(founded at 2:30 pm on February 9).
(Filtrate water* : a drop per approx. 1 second)
*Filtrate water: water which takes from dam.
