*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 approximately 2:30 am on March 23, seawater injection to the reactor
through the reactor feed water system was initiated.
-From 3:37 pm on March 25, we started injecting freshwater by a motor
driven pump which is now powered by the off-site transmission line.
Water is currently injected at approx. 3.5m3/h through reactor feed water
system piping arrangement.
-We commenced injection of nitrogen gas into Primary Containment Vessel at
1:31am on April 7.
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.
-From 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. From 2:25pm on July 17, the motor driven pump
of Unit 2 is injecting the freshwater to the Unit 1 and 2 reactors.
-At 9:35 am on July 23, since the volume of injected water into the
reactor was found to be decreased, we adjusted the volume up to 3.8m3/h.
Hence, water is currently injected at approx. 3.8m3/h through reactor
feed water system piping arrangement.
-At 8:06 pm on June 28, we started injecting nitrogen gas into the Primary
Containment Vessel.
Unit 3 (Shut down)
-Explosive sound and white smoke were confirmed at approximately 11:01am
on March 14. It was assumed to be hydrogen explosion.
-From 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.
Water is currently injected at approx. 9.0m3/h through reactor feed water
system piping arrangement.
-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 approximately 6:00 am on March 15, we confirmed the explosive sound
and the sustained damage around the 5th floor rooftop area of Reactor
Building.
-At this moment, we do not consider any reactor coolant leakage inside the
primary containment vessel has occurred.
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
(C) 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 Pump (B).
-At this moment, we do not consider any reactor coolant leakage inside the
primary containment vessel has occurred.
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
(B) of Unit 6 in order to cool the spent fuel pool.
-At 7:27 pm on March 20, the reactor achieved cold shutdown.
-At this moment, we do not consider any reactor coolant leakage inside the
primary containment vessel has occurred.
Operation for cooling the spent fuel pools
-At 5:21 pm on May 31, we started cyclic cooling of the spent fuel pool in
Unit 2 using alternative cooling system for fuel pool cooling and
filtering system.
-At 7:47 pm on June 30, we started cyclic cooling of the spent fuel pool
in Unit 3 using alternative cooling system for fuel pool cooling and
filtering system.
-We will continuously conduct further water spray depending on the
conditions of spent fuel pools, if needed.
Others
-At 11:00 am on May 10, we started transferring accumulated water from the
underground level of reactor building to the radiation waste treatment
facility of Unit 6.
-At approximately 10:00 am on June 13, we started the operation of the
circulating seawater purification facility installed at the screen area
of Unit 2 and 3.
-From 8:00 pm on June 17, we started operation of water treatment of
accumulated water at accumulated water treatment facility.
-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 4:53 pm on July 22, we started transferring accumulated water at Unit 3
turbine building vertical shaft to the Centralized Radiation Waste
Treatment Facility (Process Main Building).
-At 4:56 pm on July 22, we started transferring accumulated water at Unit 2
turbine building vertical shaft to the Centralized Radiation Waste
Treatment Facility (Process Main Building).
-From 11 am to 6 pm on July 23, we transferred accumulated water from the
turbine building of Unit 6 to the temporary tank.
-Water treatment facility, which was stopped for the work to restore
double circuit of Yonomori line which is power source for Unit 5 and Unit
6, started its operation at 3:56 pm on July 23, and the treatment of
accumulated water was resumed at 4:27 pm.
-We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.