*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.
- 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 6, in order to make nuclear reactor flooded to the
top of Fuel range, we have increased the amount of injecting freshwater
from approximately 6m3/h to approximately 8m3/h.
- At 1:28 pm on May 15, we have increased the amount of freshwater
injected into the reactor from approximately 8m3/h to approximately
10m3/h so that we can monitor the trend shift of parameters of the
Reactor Pressure Vessel as well as the Primary Containment Vessel, the
shift which would be resulted from the increase of the amount of
injected freshwater.
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.
- At 4:53 pm on May 12, as a part of work to switch the water injection
line to the nuclear 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.
The current rate of water injection is approximately 6 m3/h through the
fire extinction system piping arrangement and approximately 9 m3/h
through the reactor feed water system piping arrangement .
- At 2:33 pm on May 15, we started injecting boric acid through the fire
extinction system.
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
- At 3:07 pm on May 14, we started spraying water into the spent fuel pool
of Unit 1 with the concrete pumping vehicle. We stopped it at 3:18 pm on
the same day due to strong winds.
- We will continuously conduct further water spray depending on the
conditions of spent fuel pools, if needed.
Injured etc
- At about 6:50 am on May14, a worker of a sub-contractor became a bad
health during a carrying work for drainage treatment system in the
Centralized Environment Facility. He was carried to hospital. We
received a notice from the hospital on phone that the worker died at
9:33 am on May 14.
Others
- At 1:30 pm on April 26, we have started spraying the dust inhibitor
inside the building.
- 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 have started transferring the accumulated water
in turbine building of Unit 6 to temporary tanks.
- At 11:00 am on May 10, we have started transferring the accumulated
groundwater inside the reactor building to the radiation waste treatment
facility in Unit 6.
- We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.