*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.
-On December 22, according to the operational record thus far, we changed
the volume of nitrogen into PCV and that of gas emitted from PCV gas
control system. At 10:35 am on the same day, we decreased the nitrogen
injection amount from approx. 18Nm3/h to approx. 13Nm3/h. In addition, at
11:45 am, we confirmed the volume of gas emitted from the gas management
system decreased from approx. 30Nm3/h to 26.9Nm3/h.
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.
On December 22, we conducted the sampling of the gas management system.
According to our radionuclide analysis, Xe-135 at the entrance of gas
management system was below detection limit (1.1x10-1Bq/cm3), and we
confirmed that is below the determination criteria for recriticality such
as 1Bq/cm3.
-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 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. (From 1:30 pm to 3:15 pm on December 22, we
injected hydrazine (corrosion inhibitor))
-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.
-At 9:43 am on December 22, At the Alternative Cooling apparatus of Spent
Fuel Pool Cooling and Filtering System, since the suction force of
primary circulating pump decreased, we stopped the pump to conduct
flushing of entrance-side strainer of primary circulating pump and
stopped cooling of spent fuel pool. (The temperature of pool is approx.
13°C when the pump stopped)
Then, we flushed the strainer so that the suction force recovered. Thus,
at 11:06 am on the same day, restarted the pump and began to cool the
spent fuel pool. (The temperature of pool is approx. 13°C when the pump
restarted)
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 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.
-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).
-At around 1:40 am on December 21, the alarm went off at the desalination
facility (reverse osmosis membrane type) 2-2 which showed that the
closing of the backwash water drain valve of the multimedia filter was
not conducted within the designated time, which led to an automatic
shutdown of the unit. We confirmed at the site that there was no water
leak. Since we have enough desalinated water this will not influence the
water injection. Desalination facility (reverse osmosis membrane type) 3
can be activated. Then, as the result of valve activity confirmation
investigation, there is no fault in the facilities. Therefore, we
considered the phenomenon is transient. At around 10:20 am on the same
day, we restarted the unit. We will continue to monitor operation status.
-At 10:00 am on December 22, we started to replace the transmission parts
of monitoring post No.2 and No.8 which monitor dose rate inside the site.
At 11:40 on the same date, we finished the replacement work. In addition,
monitoring post No.8 data was unavailable from 11:10 am to 11:40 am, but
we confirmed that the other monitoring posts didn't indicate unusual
values. Monitoring post No.2 was available during the replacement work
due to the replacement parts are different from Monitoring post No.8.
