*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. 3.8 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.
From 5:52 am to 8:33 am on August 3, the nitrogen gas supply was stopped
due to switching work of nitrogen gas injection equipment to spare one.
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 is currently injected at approx. 3.7 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.
From 5:52 am to 8:29 am on August 3, the nitrogen gas supply was stopped
due to switching work of nitrogen gas injection equipment to spare one.
(However, from 5:38 am to 8:27 am, the nitrogen gas injection was
continued by using alternative gas supply line.)
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 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.
From 5:52 am to 8:29 am on August 3, the nitrogen gas supply was stopped
due to switching work of nitrogen gas injection equipment to spare one.
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 4:10 pm on July 30 to 6:49 pm on August 2, we transferred
accumulated water at Unit 2 turbine building to Centralized Radiation
Waste Treatment Facility.
- From 4:13 pm on July 30, we started transferring accumulated water at
Unit 3 turbine building to Centralized Radiation Waste Treatment Facility.
- From 10 am to 5 pm on August 2, we transferred low level accumulated
water from temporary outside tank to mega-float.
- At 10 am on August 3, we started transferring of low level accumulated
water from temporary outside tank to mega-float.
- From 11 am to 4 pm on August 2, we transferred accumulated water from
Unit 6Turbine Building to the temporary tank.
- At 11 am on August 3, we started transferring accumulated water from
Unit 6 Turbine Building to the temporary tank.