*Updates from previous press release 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.
At 10:06 am on July 17, as we confirmed that the rate of water injected
into the reactor decreased to approx 3.0 m3/h, we adjusted the water
injection rate at approx 3.8 m3/h. After that, at 2:25 pm, we adjusted
the water injection rate at approximately 4.0 m3/h as we changed the
water injection line.
Water is currently injected at approx. 4.0m3/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. At 6:27 pm on June 23, we changed the water injection line so
that we could inject water to Unit 1 and 2 by a motor driven pump by
which we had been injecting water into Unit 1 (the motor driven pump for
Unit1) and suspended a motor driven pump by which we had been injecting
water into Unit 2 (the motor pump for Unit 2).
At 2:25 pm July 17, we stopped the motor pump for Unit 1 and started the
motor pump for Unit 2 so that we would change the power source of the
suspended water injection line to the motor pump for Unit 2. We also
adjusted the water injection rate at approximately 4.0 m3/h.
Water is currently injected at approx. 4.0m3/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 m3/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.
-Regarding the Residual Heat Removal System, we had been utilizing
temporary sea water cooling pump, however, at 10:16 am on July 15, we
recovered the original Residual Heat Removal System Pump (B) and started
it at 2:45 pm.
-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.
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 June17, 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 11:22 am to 3:52 pm on July 16, we injected fresh water into the
Reactor Well and the Drier Separator Pit of Unit 4, in order to reduce
the radiation dose at the 5th floor of the Unit 4 Reactor Building.
-At 4:24 am on July 17, in accordance with the work for transmission
rerouting of the offsite power for Unit 5 and 6 (enhancement of offsite
power), we switched the on-site power for Unit 5 and 6 to power receiving
from two diesel generators. At 1:20 pm, after completing the work, we
restored receiving offsite power as on-site power for Unit 5 and 6.
-We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.