* 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.
At 5:05 am of December 21, decrease in water injection was confirmed and
we adjusted water injection from the reactor feed water system from
approx 4.3 m3/h to 4.5 m3/h, and water injection from the core spray
system from approx. 1.8 m3/h to 2.0 m3/h.
The current water injection volume is approx 4.5 m3/h from the reactor
feed water system and approx. 2.0 m3/h from the core 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 control
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. 2.8 m3/h from the reactor
feed water system and approx. 6 m3/h from the core 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 3:03 pm on December 20, we stopped this system due to inspections in
the flow rate detector of the alternative cooling equipment of the Fuel
Pool. This is scheduled to last until around 2:00 pm of December 23 and
during this time we are expecting that the temperature of the spent fuel
pool will rise by 21 °C ( temperature at the time the we stopped the
system: 15.4 °C).
- 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.
- On December 21, regarding nitrogen injection to the PCV and gas exhaust
amount from the PCV gas controlling system, change in nitrogen injection
amount and gas exhaust amount from the gas controlling system was
conducted based on the past operation. At 2:52 pm on the same day,
injection of nitrogen to the PCV was adjusted from approx. 16 m3/h to
approx. 10 m3/h. At 3:15 pm. A gas exhaust amount from gas controlling
system was adjusted from approx. 40 m3/h to approx. 32 m3/h.
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 2.9m3/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 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 2:45 pm on July 15, we started the operation of the original Residual
Heat Removal System (System B) by its original seawater pump.
- At 11:28 am on December 21, trial operation was conducted for Unit 5
residual heat removal system pump (A) which has been stopped due to the
tsunami on March 11. Because its soundness was confirmed, it was resumed
to be on stand-by at 12:49 pm. Reactor cooling was temporarily suspended
while switching pumps in trial operation, but there is no problem
regarding the cooling.
- 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.
- At 1:57 pm on December 21, transfer of accumulated water was started from
Unit 2 turbine building to the Centralized Radiation Waste Treatment
Facility (Miscellaneous Solid Waste Volume Reduction Treatment Building
[High Temperature Incinerator Building] and Process Main Building).
