*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. 3.7 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.
Water is currently injected at approx. 3.8 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.
Water is currently injected at approx. 7 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 (System 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. (From 10:35 am to 0:29 pm on Aug 24, we injected
hydrazine (corrosion inhibitor) as well.)
- 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 12:44 pm 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 Units 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 7:41 pm on August 19, we started treatment of accumulated water by
parallel operation of one line from the cesium adsorption instrument to
the decontamination instrument and the other treatment line of the 2nd
cesium adsorption instrument.
- At approximately 4:00 pm August 23, we confirmed that Water Desalination
1B (Type of Reverse Osmosis Membrane) had stopped. We adjusted a water
flow rate control device and at 6:20 pm on the same day, we restarted the
facility.
- At 4:19 pm on August 18, we transferred accumulated water from the
turbine building of Unit 2 to Central Radioactive Waste Treatment
Facility.
- At 11:34 am on August 20, we started operation of the desalting facility
for the spent fuel pool of Unit 4
- At 9:39 am on August 21, we started transfer of accumulated water from
the turbine building of Unit 3 to Miscellaneous Solid Waste Volume
Reduction Treatment Building (High Temperature Incinerator Building), but
temporarily suspended the transfer and confirmed the system structure. On
August 23, we started two transfer pumps and started transferring to
Solid Waste Volume Reduction Treatment Building (High Temperature
Incinerator Building) and Process Main Building in Centralized Radiation
Waste Treatment Facility.
Then at 9:30 am on August 24, we stopped transferring to Solid Waste
Volume Reduction Treatment Building (High Temperature Incinerator
Building) and changed the transfer to Process Main Building in
Centralized Radiation Waste Treatment Facility by two transfer pumps.
- At 10:00 am on August 23, we started transfer of accumulated water from
the turbine building of Unit 6 to temporary tanks.
