* 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.
Current water injection volume is approx. 4.5 m3/h from the reactor feed
water system and approx. 2 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.
Current water injection volume is approx. 0.3 m3/h from the reactor feed
water system and approx. 9 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.
Current water injection volume is approx 2.9 m3/h from the reactor feed
water system and approx. 6 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.
As a trend in decrease of Primary Circulation Pump's suction pressure is
continuing at this device, at 11:46 am on January 5, 2012, we
temporarily stopped the SFP cooling by shutting down the pump for a
replacement of the strainer at the pump's inlet. We plan to continue the
pump's shutdown until January 7, while the expected temperature increase
at the SFP water is around 0.25°C (SFP water temperature: 23.7°C)
- 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.
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.
- At this moment, we do not think there is any reactor coolant leakage
inside PCV.
Others
- At around 10 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 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.
- Since December 22, 2011, the atmospheric temperatures at point C of
Unit 1 Primary Containment Vessel (PCV) monitored by the Containment
Atmospheric Monitoring System had risen (the atmospheric temperature of
the PCV on December 22 was approx. 38°C, at 7 pm on December 27 was
approx. 49°C). The other temperatures had not risen, so we conducted a
survey checking the reliability of the meters from 9 am to 10 am on
December 28, and we confirmed that there are no problems. From 11:00am
to 12:15pm on the same day, we adjusted the volume of Nitrogen injection,
from approx. 8 Nm3/h to approx.18 Nm3/h, and emission of the gas
management system, from approx. 23 Nm3/h to approx.30 Nm3/h, in order to
identify the cause by monitoring the system with the same injection and
emission volume as before December 22. The temperature went up to approx.
54.6°C at 6:00 pm on December 28 at its maximum and fell to approx.
42°C as of 5:00 am on January 6, 2012. Temperatures at other two points
also indicated slight increases but are currently in the stable status.
Point D: (Maximum) approx. 35.8°C at 5:00 pm on December 29, 2011 →
approx. 31.5°C at 5:00 am on January 6, 2012.
Point E: (Maximum) approx. 40.0°C at 5:00 pm on December 29, 2011 →
approx. 34.5°C at 5:00 am on January 6, 2012.
While we think the reason for the temperature increase was due to the
changes in the volume of nitrogen inclusion and exhaust from PCV, we
will continuously conduct the survey for the cause of temperature
increase and monitoring of the plant.
- At 10:01 am on January 3, 2012, we started to transfer accumulated water
from the basement of turbine building of Unit 3 to the Centralized
Radiation Waste Treatment Facility (Miscellaneous Solid Waste Volume
Reduction Treatment Building [High Temperature Incinerator Building] and
the Process Main Building).
- From 10:00 am to 4:00 pm on January 4, 2012, we transferred accumulated
water from the basement of turbine building of Unit 6 to temporary tank.
- At 9:30 am on January 5 2012, we started transferring accumulated water
from the ground floor of the turbine building of Unit 2 to the
Centralized Radiation Waste Treatment Facility (Miscellaneous Solid
Waste Volume Reduction Treatment Building [High Temperature Incinerator
Building] and the Process Main Building) .
- At 9:15 am on January 6, 2012, We started a dust sampling at the rooftop
of Unit 3 Turbine Building by using a large crane.
