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 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 freshwater by a motor driven pump powered by the
off-site transmission line.
At 6:27 pm on June 23, we changed the water injection line so that we can
inject water to Unit 1 and 2 by the motor driven pump for Unit 1 and
stopped the motor driven pump for Unit 2.
Water is currently injected at approx. 3.5m3/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 m3/h through reactor feed water
system piping arrangement.
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 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.
-From2:45 pm to 3:53 pm on June 29, we injected water into Unit 3 using a
temporary motor driven pump.
-We will continuously conduct further water spray depending on the
conditions of spent fuel pools, if needed.
Others
-At 1:30 pm on April 26, we started spraying the dust inhibitor inside the
site.
-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 June17, we started operation of water treatment of
accumulated water at accumulated water treatment facility.
-At 9:56 am on June 22, we started transferring accumulated water in
turbine building of Unit 2 to central waste treatment facility building.
-At approximately 12:00 pm on June 28, since we found the water level
indicator (manometer) of the temporary tank to which the accumulated
water of the turbine building of Unit 6 was transferred fallen down, we
closed the valve and stopped the water leakage from the indicator.
-In light of the water leakage event at the drain of lower part of the
primary storage tank for water desalinations reverse osmosis membrane
concentrated water in the accumulated water treatment system at around
9:30 am on June 29, during the survey for the existence of similar event,
at 5:40 pm, we found small leakage of water from lower part of stoppage
flange of another storage tank, we stopped the leakage and installed a
saucer at the lower part of the flange.
-Since an alarm showing water leakage was sounded in the On-site Bunker
Building at 2:49 pm, the accumulated water treatment system was manually
stopped at 2:53 pm.
The cause of this incident is estimated that treated water, overflowed
from the tank to the saucer, triggered the alarm when the manhole was
opened during the inspection of the treated water tank of the coagulation
settling facility.
At 6:45 we swiped the accumulated water in the saucer and restart the
facility after stopping the alarm. However, we manually stopped it again
at 6:54 pm, since equipments that constituted the facility did not work
well.
At 9:15 pm, we restarted the facility after confirming no abnormal issues
on that.
-At 8:56 am on June 30, we started transferring the accumulated water from
the basement of the turbine building of Unit 3 to Centralized Radiation
Waste Treatment Facility (Process Building).
-At 9:00 am on June 30, we stopped the water desalination system to treat
the concentrated saltwater in the storage tank of the system.
-We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.