*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 reactor 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.
The current rate of water injection is approx. 5 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.
- The current rate of water injection is approx. 5 m3/h through the reactor
feed water system piping arrangement.
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.
- The current rate of water injection is approx. 11.5 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 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
- At 5:21 pm on May 31, we started cyclic cooling of the spent fuel pool in
Unit 2 using alternative cooling system for fuel pool cooling and
filtering system.
- From 2:34 pm to 3:54 pm on June 1, we injected water to the spent fuel
pool of Unit 3 by a temporary motor driven pump (from 2:41 pm to 3:26 pm,
we added hydrazine (antioxidant).
- 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 27, 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.
- At 8:00 am on May 31, 2011, we confirmed oil leakage to the sea around
the curtain wall of the water intake canal of Unit 5 and 6, Fukushima
Daiichi Nuclear Power Station. As a result of our investigation, we
confirmed that oil leaked from pipes around seawall to the port through
holes of steel sheet piles and that the leakage already stopped. Since
the diffused area was just around the curtain wall and the surface of the
sea around Shallow Draft Quay and the oil film was very thin, we
confirmed that there is no spread to the outer sea. We completed
installing oil-absorbing mat around seawall at approximately 2:00 pm and
also installed oil fences at 4:50 pm. We plan to protect pipes around
seawall and collect the oil.
- At 12:50 pm on June 2, 2011, we commenced the transfer of contaminated
water from Unit 3 turbine building condenser to Unit 3 condensate storage
tank.
- We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.