*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 by a motor
driven pump which is now powered by the off-site transmission line.
Water is currently injected at approx. 3.7m3/h through reactor feed water
system piping arrangement.
- We commenced injection of nitrogen gas into Primary Containment Vessel
at 1:31am on 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 fresh water by a motor driven pump powered by the
off-site transmission line. From 2:25pm on July 17, the motor driven pump
of Unit 2 is injecting the freshwater to the Unit 1 and 2 reactors.
Water is currently injected at approx. 3.8m3/h through reactor feed water
system piping arrangement.
- At 8:06 pm on June 28, we started injecting nitrogen gas into the Primary
Containment Vessel.
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.
Water is currently injected at approx. 9.0m3/h through reactor feed water
system piping arrangement.
- At 8:01 pm on July 14, injection of nitrogen gas into the Primary
Containment Vessel started.
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 has occurred.
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 2:45 pm on July 15, we started the operation of the original Residual
Heat Removal System Pump (B).
- At this moment, we do not consider any reactor coolant leakage inside the
primary containment vessel has occurred.
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 has occurred.
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.
- At 7:47 pm on June 30, we started cyclic cooling of the spent fuel pool
in Unit 3 using alternative cooling system for fuel pool cooling and
filtering system.
- We will continuously conduct further water spray depending on the
conditions of spent fuel pools, if needed.
Injury accident
- Around 10:06 am on July 18, a worker of the partner company fell from
the distribution pole during the connection work of the optical cable
near the observatory entrance of the station. He was transported to the
Iwaki Kyouritsu Hospital by the helicopter emergency medical service
(called "Doctor Heli").
Others
- At 11:00 am on May 10, we started transferring accumulated water from
the underground level of reactor building to the radiation waste treatment
facility of Unit 6.
- At approximately 10:00 am on June 13, we started the operation of the
circulating seawater purification facility installed at the screen area
of Unit 2 and 3.
- From 8:00 pm on June 17, we started operation of water treatment of
accumulated water at accumulated water treatment facility.
- At 6:00 pm on July 2, we started the circulating injection cooling to
inject the water, which was treated by the accumulated water treatment
system, to the reactors through the buffer tank.
- At 10:50 am on July 16, we started transfer of the accumulated water from
the Turbine Building of Unit 3 to the Process Main Building of the
Centralized Radiation Waste Treatment Facility.
- At 10:56 am on July 16, we started transfer of the accumulated water from
the Turbine Building of Unit 2 to the Process Main Building of the
Centralized Radiation Waste Treatment Facility.
- From 8:30 am on July 18, we started an installation work of a temporary
roof for the Unit 3 turbine building in order to cover the roof's opening
as a measure for rainwater.
- On July 21, in order to conduct a restoration work for double circuit of
Yonomori line which is power source for Unit 5 and Unit 6, we started
a power switching work to stop the operation of Okuma Line No.3 which
was connected to Yonomori Line No.1. According to this work, we stopped
the alternative cooling system for the fuel pool cooling and filtering
system of Unit 3 at 8:02 am, the water treatment system at 8:38 am, and
the cooling system for the common pool at 8:40 am. After that, upon
starting of power receiving from Okuma Line No.2, we started the cooling
system for the common pool at 2:41 pm, and the alternative cooling system
for the fuel pool cooling and filtering system of Unit 3 at 2:52 pm.
- At 11:00 am on July 21, we started transferring accumulated water from
the Turbine Building of Unit 6 to temporary tanks.
- We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.
