*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 13.5 m3/h through the reactor feed water
system piping arrangement. (The description of water injection volume
has been changed from approximately 12 m3/h to approximately 13.5 m3/h.
As a monitoring point and an instrument were changed, the value of
instrument reading has been changed, but we have not conducted any
operations regarding flow rate adjustment)
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
- From 4:36pm to 8:04pm, on May 25, we sprayed water to Unit 4 by a
concrete pumping vehicle (from 4:42pm to 6:49pm, injected hydrazine
[corrosion inhibitor] at the same time).
- We will continuously conduct further water spray depending on the
conditions of spent fuel pools, if needed.
Injured
- We announced on May 23 that a worker who was unloading a tank had his
left hand injured and was transferred to Iwaki Kyouritsu Hospital, On
May 24, he was diagnosed as "crushed wound on his left thumb" with the
prospect of one-month hospital visit.
Others
- At 1:30 pm on April 26, we started spraying the dust inhibitor inside
the site.
- Since 10:08 am on April 19, we had been transferring high level
radioactive wastewater from the vertical shaft near the turbine
building of Unit 2 to the Centralized Radiation Waste Treatment
Facility. At 9:05am on May 25, a transferring operation was suspended
due to the changes in power source composition but was resumed at 3:30
pm.
- 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.
- Since 6:04 pm on May 17, we had been transferring high level radioactive
waste water from the underground level of the turbine building of Unit 3
to the Centralized Radiation Waste Treatment Facility, but the transfer
was suspended due to an inspection on transmission lines and buildings
at 9:10 am, on May 25.
- We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.