*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 powered by the off-site transmission line. We are now
injecting freshwater by a motor driven pump powered by the off-site
transmission line. Current injected water amount is approx. 4.5 ㎥/h
through feed water system.
-As it was suspected that hydrogen gas had been accumulated inside Primary
Containment Vessel, in order to prevent increase in density of oxygen, we
commenced the valve opening operation concerning injection of nitrogen
gas into the primary containment vessel at 10:30 pm on April 6 and
commenced injection 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.
The current rate of water injection is approx. 5 ㎥/h through the reactor
feed water system piping arrangement.
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.
The current rate of water injection is approx. 11.5 ㎥/h through the
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.
-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. On May 27, we started spraying dust inhibitor to Turbine Building
of Units 1. We will implement spraying the dust inhibitor to other
turbine and reactor buildings of Units 1 to 4.
-At 2:00 pm on May 1, we started transferring accumulated water in the
turbine building of Unit 6 to temporary tanks.
-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.
-From 6:39 pm on June 4 to 8:40 am on June 16, transfer of accumulated
water from vertical shafts (trenches) of turbine building of Unit 2 to
Process Main Building was conducted.
-At 12:42 pm on June 11, we started to operate local exhausters in order
to improve inside environment of Unit 2 Reactor Building.
-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 10:05 am on June 14 to 8:46 am on June 16, transfer of accumulated
water in the Unit 3 turbine building to the centralized radiation waste
treatment facility was conducted.
-From 10:33 am on June 15 to 9:52 am on June 16, transfer of accumulated
water in the Unit 1 condenser to condenser storage tank was conducted.
-At 11:05 am on June 15, it was confirmed that a worker from a partner
company in charge of crane assembling work for the preparing the
installation of the cover in Unit 1 reactor building at shallow draft
quay was smoking without his full mask. However, the result of whole
body counter examination showed a slight amount of internal exposure
dose and we confirmed that the amount has no adverse effect on the body.
-We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.