*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. It was assumed to be hydrogen explosion.
- At 3:37 pm on March 25, 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, 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 volume is approx. 4.3 m3/h from the reactor
feed water system and approx. 2 m3/h from the core spray system.
At 9: 44 am on December 30, the injected water amount was adjusted from
approx. 4.4 m3/h to approx.4.5 m3/h in feed water system, from approx.
1.8 m3/h to approx.2.0 m3/h in corer spray system as the change in the
injected water amount was observed.
Current water injection amount is approx.4.5 m3/h in feed water system
and approx.2.0 m3/h in corer spray system
- We commenced injection of nitrogen gas into Primary Containment Vessel
at 1:31 am on April 7.
- At 11:22 am on August 10, 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, 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, we started operation to inject nitrogen into
the reactor pressure vessel.
- At 6:00 pm on December 19, a full-scale operation of the PCV gas
management system started.
Unit 2 (Shut down)
- At approximately 6:00 am on March 15, an abnormal noise began emanating
from nearby Pressure Suppression Chamber and the pressure within the
chamber decreased.
- At 10:10 am on March 26, 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, 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 volume is approx. 1.8 m3/h from the reactor
feed water system and approx. 7.0 m3/h from the core spray system.
At 9: 44 am on December 30, the injected water amount was adjusted from
approx. 1.8 m3/h to approx.2.0 m3/h in feed water system (no change in
corer spray system with approx. 7.0 m3/h) as the change in the injected
water amount was observed.
Current water injection amount is approx.2.0 m3/h in feed water system
and approx.7.0 m3/h in corer spray system
- At 5:21 pm on May 31, 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, we started injecting nitrogen gas into the Primary
Containment Vessel.
- At 6:00 pm on October 28, we put the gas management system of the reactor
containment vessel in operation.
- At 10:46 am on December 1, 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. It was assumed to be hydrogen explosion.
- At 6:02 pm on March 25, 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, 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 volume is approx 3 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, 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 10:27 am on December 30, since inlet pressure of the primary
circulation pump was decreasing in the alternative cooling system of the
spent fuel pool cooling and filtering system, cooling of the spent fuel
pool was stopped by shutting down the pump, in order to flush the inlet
strainer of the primary circulation pump. (Temperature of the spent fuel
pool was approx. 13.0°C at the time of shutdown.)
Flushing was conducted subsequently, and since inlet pressure of the pump
was recovered, cooling of the spent fuel pool resumed by restarting the
pump, at 1:42 pm of the same day. (Temperature of the spent fuel pool was
approx. 13.1°C at the time of restart.)
- At 8:01 pm on July 14, injection of nitrogen gas into the Primary
Containment Vessel started.
- At 4:26 pm on November 30, 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, 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, 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. (From 1:28 pm to 3:07 pm on December 28,
we conducted injection of hydrazine to spent fuel pool of Unit 4 through
the circulating cooling system.)
- At 10:58 am on November 29, 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, we started the Residual Heat Removal System Pump
in order to cool the spent fuel pool.
- At 2:45 pm on July 15, 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, 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, we started the Residual Heat Removal System Pump
of Unit 6 to cool down Spent Fuel Pool.
- At 2:33 pm on September 15, 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, 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, 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, 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, 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, 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, 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, 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 pm on
December 28 at its maximum and fell to approx. 48.4°C at 11 am on
December 30. 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 →
approx. 34.5°C at 11:00 am on December 30.
Point E: (Maximum) approx. 40.0°C at 5:00 pm on December 29 →
approx. 38.4°C at 11:00 am on December 30.
We will continuously conduct the survey for the cause of temperature
increase and surveillance of the plant.
- At 3:22 pm on December 28, we started to transfer accumulated water from
the basement of 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 2:37 pm on December 30, we started the transfer of the accumulated
water from the basement of turbine building of Unit 3 to the Centralized
Radiation Waste Treatment Facility (the Miscellaneous Solid Waste Volume
Reduction Treatment Building [High Temperature Incinerator Building] and
the Process Main Building).
