*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 7.8 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.
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. 3 m3/h through reactor feed water
system piping arrangement, and at approx. 7.3 m3/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.
-At 12:53 pm on October 28, we activated the exhaust fan of the gas
management system of the reactor containment vessel in the reactor
building and started test operation. As we confirmed stable operation of
the system, from 6:00 pm on the same day, we put the system in operation.
-As the hydrogen density of the emission from the gas controlling system
for Reactor of Unit 2 increased from 2.7% (at the time when nitrogen was
previously included at 6:10 am on October 30) up to 2.9% at 4:30 pm on
November 3, we increased the volume of nitrogen inclusion into Reactor
from 21Nm3/h to 26 Nm3/h at 4:50pm on the same day so that the hydrogen
density of the emitted gas won't go over the combustible threshold
concentration (4%).
-At 2:20 pm on November 4, in order to balance between the amount of
nitrogen injection into Reactor Pressure Vessel and that of emission from
the gas control system, we increased the gas emission amount from 14Nm3/h
to 22Nm3/h.
-At 11:04 am on November 6, we started operation of radioactive material
decontamination instrument of spent fuel pool.
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. 2.3 m3/h through reactor feed water
system piping arrangement, and at approx. 8 m3/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 11:25 am on November 5, we started dust sampling at the upper part of
the Reactor Building of Unit 3 by using the large crane. At 2:00 pm on the
same day, the sampling was completed.
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 11:34 am on August 20, we started an operation of desalination
equipment in the spent fuel pool.
-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 time, we don't think there is any reactor coolant leakage inside
the primary containment vessel.
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 10:11 am on November 2, we started transferring the accumulated water
from the basement of the Unit 3 turbine building to the High Temperature
Incinerator Building of the Centralized Radiation Waste Treatment Facility.
-At 9:38 am on November 4, we started transferring the accumulated water
from the basement of the Unit 2 turbine building to Centralized Radiation
Waste Treatment Facility.
-From 10:00 am to 4:00 pm on November 6, we transferred the accumulated
water from Turbine Building of Unit 6 to the temporary tanks.
-At around 11:00 am on November 6, since partner companies' workers who
went on patrol found that the boiler of evaporative concentration
apparatus stopped, we stopped operation of the apparatus 3B and 3C. Since
the operation panel on the site alerted "Very low water level in boiler
supply water tank", we assumed that the boiler stopped due to this reason.
After that, we conducted investigation of the cause of decrease of supply
tank water level. When we started a backup pump for transfer of boiler
supply water, the alert stopped. Therefore we judged that one pump was
troubled.
In addition, although all the evaporative concentration apparatus stopped,
water treatment by the water desalinations (RO membrane system) and water
injection to the reactors have been continued.
