*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 4.4 m3/h from the reactor
feed water system and approx. 1.8 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.
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.
At 10:40 am on December 14, as the decreasing of injecting water from
feed water system was confirmed, we adjusted injection rate from
approx.2.5m3/hour to approx.3m3/hour. And also adjusted injection rate
of core spray system from approx. 6.2m3/hour to approx.6m3/hour.
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 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.
6:54 am on December 14, the alert that indicates the flow difference is
big at the inlet and outlet of primary pump was issued on the alternative
cooling system of sent fuel pool. No abnormalities such as leaking etc.
were found by field inspection. Then, as we sounded the instrument piping,
we confirmed that alert stopped. Hereafter we will check flow rate once
an hour. In addition to this, keeping operation of spent fuel pool
alternative cooling system so there is no problem on cooling
-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.
The current water injection volume is approx 2.7 m3/h from the reactor
feed water system and approx. 6.0 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 2:30 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.
-With recovery work of residual heat removal sea water pump (B) which was
unavailable caused by Tsunami, we stopped residual heat removal pump (B)
and residual heat removal sea water pump (D) sequentially from 6:29 am on
December 14. The stop time will be approx. 10 hours and we expect that
the elevation of temperature is about 1.6 degree C/ hour, so we expected
there is no impact on reactor.
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. At 7:51
am on December 13, we stopped the transfer of the 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]) in order to
stop power supply to Unit 2 accumulated water transfer pump for power
supply enhancing work. With the stoppage of the water transfer, the 2nd
Cesium adsorption apparatus was shutdowned for replacing vessels at 8:44
am on December 12, and will be kept outage until December 14 in order to
adjust the water level of the centralized radiation waste treatment
facility (miscellaneous solid waste Volume reduction treatment building
[high temperature incinerator building]). The Cesium adsorption apparatus
is continued its operation. Water injection to the Reactors will not be
affected since the cooling is continued by using processed water in the
buffer tank.
-From 10:00 am to 4:00 pm on December 13, we had transferred accumulated
water from the Turbine Building of Unit 6 to the temporary tank.
-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.
