* 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. The current water injection volume is approx
4.3 m3/h from the reactor feed water 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.
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, we started injecting water to the reactor
through core spray system water injection piping arrangement in addition
to the water injection through reactor feed water system piping
arrangement.
Water is currently injected at approx. 2.9m3/h through reactor feed water
system piping arrangement, and at approx. 4.3m3/h through core spray
system water injection piping arrangement.
- 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.
- From 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.
Water is currently injected at approx. 2.1m3/h through reactor feed water
system piping arrangement, and at approx. 6m3/h through core spray system
water injection piping arrangement.
- 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 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.
- 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 2:30 pm on March 20, the reactor achieved cold shutdown.
- 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 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 7:27 pm on March 20, the reactor achieved cold shutdown.
- 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 6:03 pm on November 30, we started transfer of the accumulated water
from the basement of Unit 2 turbine building to Centralized Radiation
Waste Treatment Facility High Temperature Incinerator Building.
- We plan to establish the system injecting water into the reactor in Unit
1 to 3 using the condensate storage tank of Unit 3. In preparation of
such establishment, the stored water in the tank was transferred to the
basement of turbine building of Unit 3 from 10:22 am on November 21 to
9:45 am on November 24. As the calibration of water level gauge is
required if all the water is transferred, approx. 200 ton was left in the
tank. During the measurement of salt concentration in the left water, it
turned out that concentration was high. In order to secure the space for
additional water injection to decrease such concentration, at 10:00 am on
December 6, the left water was transferred from the tank to the basement
of the turbine building of Unit 3.
At 8:54 on December 7, we stopped transferring, and at approx. 9:19 am on
the same day, we started filling water in the tank, but afterwards, we
confirmed water leakage (approx. 5 liter) at the joint section of hose
connecting to the tank, at approx. 9:52 am, we stopped filling water and
confirmed the leakage has stopped. We plan to consider such measures as
repair etc. in future. The leaked water was treated as to be free of
radioactive materials and desalinated. At 9:05 am on December 9, we
restarted filling the water in the tank after completing the replacement
of the transfer hose. At 7:00 pm on the same day, we finished the filing.
- From 10:00 am on December 8 to 4:00 pm on December 9, we transferred
accumulated water from the Unit 6 turbine building to the temporary tank.
- At 9:00 am on December 10, we started dust sampling above the reactor
building of Unit 3 with a large crane.
