*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 feed water system was initiated.
-From 3:37 pm on March 25, we started injecting freshwater. We are now
injecting freshwater by a motor driven pump powered by the off-site
transmission line at 6 m3/h.
-As it is suspected that hydrogen gas is accumulated inside Primary
Containment Vessel, we commenced the valve opening operation concerning
injection of nitrogen gas into the primary containment vessel at 10:30 pm
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 at 7 m3/h.
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.
-At 4:53 pm on May 12, as a part of work to switch the water injection
line to the reactor from the fire extinction system to the reactor feed
water system, we started water injection through the reactor feed water
system in addition to through the fire extinction system.
-On May 23rd, we changed the rate of water injection to Unit 3 through the
fire extinction system piping arrangement from approximately 4 m3/h to
approximately 3 m3/h at 5:19 Pm. The current rate of water injection is
approximately 3 m3/h through the fire extinction system piping
arrangement and approximately 12 m3/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 happened.
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 happened.
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 happened.
Operation for cooling the spent fuel pools
-On May 23rd , from 4:00pm to 7:09pm we sprayed water to the spent fuel
pool of Unit 4 by the concrete pumping vehicle (from 2:17 pm to 2:37 pm ,
we sampled, on a trial basis, radioactive materials in the ambient air at
the opening of the Reactor Building. We added hydrazine (antioxidant)
from 4:08pm to 6:30pm).
-On May 24th, from 10:15 am to 1:35 pm we injected water to Unit 3 by
temporary pumps (we added hydrazine (antioxidant) from 10:20 am to 12:56
pm).
-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 10:08 am on April 19, we started transfer of high level radioactive
wastewater from the vertical shaft near the turbine building of Unit 2 to
the Centralized Radiation Waste Treatment Facility.
-At 2:00 pm on May 1, we started transferring the accumulated water in
turbine building of Unit 6 to temporary tanks.
-At 11:00 am on May 10, we started transferring the accumulated water from
the underground level of reactor building to the radiation waste
treatment facility of Unit 6.
-At 6:04 pm on May 17, we started transfer of high level radioactive waste
water from the underground level of the turbine building of Unit 3 to the
Centralized Radiation Waste Treatment Facility.
-We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.