*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 6.5 ㎥/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. 2.5㎥/h through reactor feed water
system piping arrangement, and at approx. 6.9㎥/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.
Regarding the hydrogen concentration of the gas management system of the
reactor containment vessel in Unit 2, we confirmed that it increased to
approx. 2.7vol% at 5:00pm on October 30, which was approx. 1vol% at the
beginning of the operation. Therefore we adjusted the amount of injecting
nitrogen gas to the Primary Containment Vessel from approx.16.5 N ㎥/h to
21 N ㎥/h at 6:10 pm on October 30 in order to avoid exceeding the
combustible threshold concentration (4vol%) of hydrogen.
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. 2.5㎥/h through reactor feed
water system piping arrangement, and at approx. 8.1 ㎥/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.
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.
-At 10:12 am on October 20, we started transferring the accumulated water
from the basement of turbine building of Unit 2 to the Process Main
Building of Central Radioactive Waste Treatment Facility. At 9:32 am on
October 28, we stopped transferring the accumulated water from the
basement of turbine building of Unit 2 to the Process Main Building of
Central Radioactive Waste Treatment Facility temporarily, and after
checking the systematic diagram, at 9:54 am on October 28 we changed the
destination of transferring the accumulated water to High Temperature
Incinerator Building of Centralized Radiation Waste Treatment Facility.
-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.
-From 10:00 am to 4:00 pm on October 30, we transferred accumulated water
from the turbine building of Unit 6 to the temporarily built tank.
-At 10:00 am on October 31, we started transferring accumulated water from
the temporarily built tank to Mega-float.
