*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 nuclear
reactor through the feed water system was initiated.
-From 3:37 pm on March 25, we started injecting freshwater and are now
injecting fresh water by a motor driven pump powered by the off-site
transmission line. From on April 27, we have increased the amount of
injecting freshwater from approximately 6 m3/h to approximately 14 m3/h.
At 10:14 am on April 29, we put the amount of injecting freshwater back
to approximately 6 m3/h.
-As it is suspected that hydrogen gas is accumulated inside reactor
containment vessel, we commenced the valve opening operation concerning
injection of nitrogen gas into the reactor container vessel at 10:30 pm
April 6th and commenced injection at 1:31am April 7.
-At 10:01 am on May 6th, in order to make nuclear reactor flooded to the
top of Fuel range, we have increased the amount of injecting freshwater
from approximately 6 m3/h to approximately 8m3/h.
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.
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.
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 the Nuclear
Reactor Building.
-At this moment, we do not consider any reactor coolant leakage inside the
reactor 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 reactor cold shutdown.
-At this moment, we do not consider any reactor coolant leakage inside the
reactor 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 reactor cold shutdown.
-At this moment, we do not consider any reactor coolant leakage inside the
reactor happened.
Operation for cooling the spent fuel pools
-On May 7th, we sprayed water to Unit 4 by the concrete pumping vehicle
from 2:05 pm to 5:30 pm.
-On May 8th, we injected water to Unit 3 by temporary motor-driven pump
from 12:10 pm to 2:10 pm.
-We will continuously conduct further water spray depending on the
conditions of spent fuel pools, if needed.
Others
-The transfer of high level radioactive wastewater in Unit 2 to the
Centralized Radiation Waste Treatment Facility was temporarily suspended
at 9:22am on May 7th, due to construction of injection piping (reactor
feeding water system) to reactor of unit3. The construction work has
completed and we re-started the transfer at 4:02 pm.
-From March 27, transfer of accumulated water in Unit 5 turbine building
to a condenser has been conducted, and water with the amount of
approximately 600 m3 has been transferred from March 27 to May 2.
From May 2, we have started work relating to the set up of exhausters,
in order to improve the working environment inside the reactor building
of Unit 1. At 4:36 pm on May 5th, all of exhausters (6 units) were
started to operation.
-We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.