*New items 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 injection was arranged at approx. 3.9 ㎥/h at 9:02 am on August 5
since we observed reduction of the water injection into the reactor.
Water is currently injected at approx. 3.9 ㎥/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.
-Water injection was arranged at approx. 3.9 ㎥/h at 5:50 pm on August 4
since we observed reduction of the water injection into the reactor.
Water is currently injected at approx. 3.9 ㎥/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. 9.1 ㎥/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 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 don't think there is any reactor coolant leakage
inside the primary containment vessel.
Unit 5 (Outage due to regular inspection)
-Sufficient level of reactor coolant to ensure safety is maintained.
-At 5 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 time, we don't think there is any reactor coolant leakage inside
the primary containment vessel.
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
of Unit 6 to cool down Spent Fuel Pool.
-At 7:27 pm on March 20, the reactor achieved cold shutdown.
-At this time, we don't think there is any reactor coolant leakage inside
the primary containment vessel.
Operation for cooling the Spent Fuel Pools
-At 5:21 pm on May 31, we started cyclic cooling of Spent Fuel Pool of
Unit 2 by using alternative cooling system of the Pool's cooling and
filtering system.
-At 7:47 pm on June 30, we started cyclic cooling of Spent Fuel Pool of
Unit 3 by using alternative cooling system of the Pool's cooling and
filtering system.
-At 0:44 am on July 31, we started cyclic cooking of Spent Fuel Pool of
Unit 4 by using alternative cooling system of the Pool's cooling and
filtering system.
Others
-At 11 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 around 10 am on June 13, we started the operation of the circulating
seawater purification facility installed at the screen area of Unit 2
and 3.
-At 8 pm on June 17, we started operation of Water Treatment Facility
against the accumulated water.
-At 6 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.
-From 4:13 pm on July 30 to 7:17 am on August 4, we transferred
accumulated water at Unit 3 turbine building to Centralized Radiation
Waste Treatment Facility.
-At 7:09 am on August 4, we started transferring accumulated water at Unit
2 turbine building to Centralized Radiation Waste Treatment Facility.
-At 8:42 am on August 4, we started transferring accumulated water at Unit
3 turbine building to Centralized Radiation Waste Treatment Facility.
-At 5:32 am on August 4, we stopped Water Treatment Facility to improve
the flow rate.
After the work, we activated the facility at 3:30 pm and restarted
operation of the water treatment system at 4:13 pm. When we adjusted the
flow rate of the system at 6:55 pm, a pump of the decontamination
instruments was stopped and the whole water treatment system was shut
down. We confirmed soundness of the pump and reactivated the system at
8:30 pm, and operation of the water treatment system was restarted at
8:50 pm.
-At 2:12 am on August 5, a process alarm was activated and the water
treatment system was shut down. At 4:03 am, the system was reactivated
and the operation was restated at 4:21 am.
-Around 7 pm on 8:04, we discovered water leakage from a flange of
transfer hose of filtered water which is used to clean up salt in a
vessel of the cesium adsorption instruments in the site bunker building.
-At 10:00 am on August 5, we started water transfer of low level
radioactive water from the outside temporary tank to the Mega-float.