*Updates 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 3:37 pm on March 25, 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. 3.6 m3/h through reactor feed
water system piping arrangement.
- We commenced injection of nitrogen gas into Primary Containment Vessel
at 1:31 am on April 7.
- At 11:22 am on August 10, we started cyclic cooling for the water in the
spent fuel pool by an alternative cooling equipment of the Fuel Pool
Cooling and Filtering System.
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.
- At 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 2:59 pm on September 14, we started injecting water to the reactor
through core spray system water injection piping arrangement in addition
to the water injection through reactor feed water system piping
arrangement.
Water is currently injected at approx. 3.5m3/h through reactor feed
water system piping arrangement, and at approx. 7.1 m3/h through core
spray system water injection piping arrangement.
- At 5:21 pm on May 31, we started cyclic cooling for the water in the
spent fuel pool by an alternative cooling equipment of the Fuel Pool
Cooling and Filtering System.
- At 8:06 pm on June 28, we started injecting nitrogen gas into the
Primary Containment Vessel.
- At 5:55 pm on October 18, since we confirmed reduction of injection
volume of nitrogen gas to the primary containment vessel of Unit 2, we
adjusted the injection volume to approx.14 m3/h.
Unit 3 (Shut down)
- Explosive sound and white smoke were confirmed at approximately 11:01 am
on March 14. It was assumed to be hydrogen explosion.
- At 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.
- At 2:58 pm on September 1, we started water injection by core spray
system in addition to water injection by the reactor feed water system
piping arrangement.
Water is currently injected at approx. 2.2m3/h through reactor feed
water system piping arrangement, and at approx. 8.0 m3/h through core
spray system water injection piping arrangement.
- At 7:47 pm on June 30, we started cyclic cooling for the water in the
spent fuel pool by an alternative cooling equipment of the Fuel Pool
Cooling and Filtering System.
- 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 around 6 am on March 15, we confirmed the explosive sound and the
sustained damage around the 5th floor rooftop area of Reactor Building.
- At 12:44 pm on July 31, we started cyclic cooling for the water in the
spent fuel pool by an alternative cooling equipment of the Fuel Pool
Cooling and Filtering System. From 1:01 pm to 2:41pm on October 20, we
injected hydrazine [Anti-corrosion chemicals] to spent fuel pool.
- At 11:34 am on August 20, we started an operation of desalination
equipment in the spent fuel pool.
- 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 5:00 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 (System B) by its original seawater pump.
- At 9:05 am on October 20, we suspended the Auxiliaries Cooling System
Seawater Pump due to the intake canal inspection. At 9:13 am, we
suspended cooling the reactor by stop of the Residual Heat Removal
System Pump (D). At 9:18 am, we suspended the Residual Heat Removal
System Seawater Pump (D).
- Due to the completion of the inspection, we started the Auxiliaries
Cooling System Seawater Pump at 2:32 pm and the Residual Heat Removal
System Seawater Pump (D) at 2:47 pm on October 20. At 3:02 pm on the
same day, we restarted cooling the reactor by the Residual Heat Removal
System Pump (D). Due to the interruption, the temperature of water in
the reactor has risen by around 9°C from 22.2°C, and temperature of the
water in the spent fuel pool has raised by around 1°C from 25.5°C.
- 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 2:33 pm on September 15, we started separately cooling the reactor
through the Residual Heat Removal System and the spent fuel pool through
Equipment Cooling Water System and Fuel Pool Cooling System.
- At this time, we don't think there is any reactor coolant leakage inside
the primary containment vessel.
Others
- 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 6:00 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
cesium adsorption instrument No.2.
- At 2:06 pm on October 7, we started to spray purified accumulated water
brought from Unit 5 and 6 continually in order to prevent dust
scattering and potential fire outbreaks from the cut down trees.
- At 6:09 am on October 18, we suspended the Cesium adsorption apparatus
unit No.1 due to power reinforcement works of the water desalinations.
At 9:04 am we suspended Unit No, 2. At approximately 11:00 am, while we
were replacing the motor of the pumps (H2-2) in the skid of the
suspended Cesium absorption apparatus, a puddle of water was found in
the skid (depth approx. 15 cm, volume approx. 3 m3). We also found that
the leakage already stopped when we found the puddle of water. After
that, we interrupted the work of change of the motor and conducted
draining the water by underwater pump. The cause is currently under
investigation.
- At 1:29 pm on October 19, since we completed the reinforce work for
power source for water treatment facilities, we restarted the second
cesium adsorption apparatus.
- At 9:06 pm on October 19, in the water treatment facilities under
operation, a SMZ pump of the 4th process line of cesium adsorption
apparatus automatically stopped. A pump of the 3rd process line is
continuously operated. Water treatment by the cesium adsorption
apparatus is also continuously operated at the flow rate approx. 17m3/h
(the flow rate before the automatic stop was approx. 20m3/h).
- From 2:00 pm to 3:00 pm on October 20, we transferred the accumulated
water from the temporary tank to the mega float.
- At 10:00 am on October 20, we started transferring the accumulated water
from the basement of turbine building of Unit 3 to the High Temperature
Incinerator Building of Central Radioactive Waste Treatment Facility.
- At 10:12 am on October 20, we started transferring the accumulated water
from the basement of turbine building of Unit 2 to the Process Main
Building of Central Radioactive Waste Treatment Facility.
