*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.
- At 11:33 am on May 29th, as a part of activities to switch injection line
from fire extinction line to feed water line, we started water injection
through feed water line in addition to fire extinction line.
Currently water is being injected at approximately 7 m3/h through the
fire extinction line and approximately 5 m3/h through the reactor feed
water 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.
- 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.
- At 8:54 pm on May 28th, we changed the rate of water injection to the
reactor of unit 3 through the fire extinction system piping arrangement
from approximately 1 m3/h to 0 m3/h.
The current rate of water injection is approximately 0 m3/h through the
fire extinction system piping arrangement and approximately 13.5 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 9:14 pm on May 28, we confirmed temporary RHRS pumps were out of
service, we started replacement of these pumps with spares at 8:12 am on
May 29th and at 12:49 pm we restarted cooling reactor by RHRS system.
- 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 1:28 pm to 3:08 pm on May 28th, we started freshwater injection to
the spent fuel pool of Unit 3 by a temporary motor driven pump (we also
injected hydrazine from 1:42 pm to 2:40 pm).
- From 4:47 pm to 5:00 pm on May 28th, we conducted leakage test for
coolant purification system of Unit 1 spent fuel pool.
- From 5:56 pm to 7:45 pm on May 28th, we sprayed water to the spent fuel
pool of Unit 4 by the concrete pumping vehicle (We added hydrazine from
5:24pm to 6:53pm).
- At 11:10 am on May 29th, we started water injection by using temporary
electrical pumps to Unit 1.
- 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.
Since May 27th, we have started spraying dust inhibitor to Unit 1's
turbine building. We will implement spraying the dust inhibitor to other
buildings including Unit 1 to 4's turbine buildings as well as reactor
buildings one by one.
- 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 4:01
pm on May 26, a transferring operation was stopped.
- 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.
