*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 is currently injected at approx. 3.9 m3/h through reactor feed
water system piping arrangement.
-We commenced injection of nitrogen gas into Primary Containment Vessel at
1:31am on April 7.
-At 9:00 am on August 10, we started to assemble steel frame for the
Reactor Building Cover.
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.
-At 8:30 pm on August 12, we adjusted the rate of water injection from
reactor feed water system piping arrangement to approx. 3.8 m3/h since
decrease of the water injection rate was confirmed.
Water is currently injected at approx. 3.9 m3/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. However at 4:22 pm on August 10, we adjusted
the flow rate of injection water to the reactor.
-At 7:30 pm on August 12, we adjusted the rate of water injection from
reactor feed water system piping arrangement to approx. 9.0 m3/h since
increase of the water injection rate was confirmed.
Water is currently injected at approx. 9.1 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 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 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.
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 cooling of Spent Fuel Pool of
Unit 4 by using alternative cooling system of the Pool's cooling and
filtering system.
-At 11:22 am on Aug 10, we started cyclic cooling of Spent Fuel Pool of
Unit 1 by using alternative cooling system of the Pool's cooling and
filtering system.
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 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 8:00 pm on June 17, we started operation of Water Treatment Facility
against the accumulated water.
-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 8:42 am on August 5, we started transferring accumulated water at Unit
3 turbine building to Centralized Radiation Waste Treatment Facility.
-From 1:35 pm on August 9 to 5:00 pm on August 12, we transferred low
level accumulated water from outdoor temporary tanks to Mega Float.
-At 4:47 pm on August 10, we started transferring of accumulated water
from turbine building of unit 2 to Centralized Radiation Waste Treatment
Facility.
-From 10:00 am to 4:00 pm on August 12, we transferred accumulated water
from Unit 6 turbine building to temporary tank.
-At 6:17 pm on August 12, the water treatment facility stopped due to a
process error alarm. However, since nothing abnormal was confirmed, we
started the water treatment facility at 10:59 pm and resumed the
treatment of accumulated water at 11:33 pm.