*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.
At 7:03 am on November 24, the injection amount by the feed water system
decreased from 5.5 m3/h to 5.0 m3/h to lower the hydrogen density of RPV
by increasing the temperature and the steam ratio thereby.
The current water injection volume is approx 5 m3/h from the reactor
feed water system.
- 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.
- On October 28, we completed installation of the cover for the Reactor
Building in order to contain dispersion of radioactive substances.
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.
At 7:11 am on November 24, in order to lower the hydrogen density of RPV
by increasing the temperature and the steam ratio thereby, the water
injection amount by the reactor core system decreased from 7.2 m3/h to
5.6 m3/h (the injection of feed water system is continuing at 2.9 m3/h)
Water is currently injected at approx. 2.8 m3/h through reactor feed
water system piping arrangement, and at approx. 5.5 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.
- From 6:00 pm on October 28, we put the gas management system of the
reactor containment vessel in operation.
- At 11:04 am on November 6, we started operation of radioactive material
decontamination instrument of spent fuel pool.
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.
At 7:19 am on November 24, in order to lower the hydrogen density of RPV
by increasing the temperature and the steam ratio thereby, the water
injection amount by the reactor core system decreased from 8.5 m3/h to
6.7 m3/h. (the injection of feed water system is continuing at 2.3 m3/h).
At 7:09, as the amount of nitrogen included was smaller than that of
Units 1 and 2, the amount increased from 14 m3/h to 28.5 m3/h.
Water is currently injected at approx. 2.1 m3/h through reactor feed
water system piping arrangement, and at approx. 6.8 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. (Hydrazine was also injected from 1:31 pm
to 3:05 pm on November 24)
- 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 this moment, 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 moment, we do not think there is any reactor coolant leakage
inside PCV.
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.
- On October 28, we started installation of the water proof wall at the
sea side, in front of the existing shore protection, Units 1-4, in order
to contain marine pollution by underground water.
- At 9:10 am on November 10, we started transfer of accumulated water from
the basement of Unit 2 turbine building to Centralized Radiation Waste
Treatment Facility High Temperature Incinerator Building.
- At 9:25 am on November 15, we started transfer of accumulated water from
basement of Unit 3 turbine building to Centralized Radiation Waste
Treatment Facility Building.
- Water treatment facilities suspended at 6:30 am on November 25 to switch
the power source of Ookuma 2 line movable transformer. The cesium
adoption apparatus resumed after switching power source to Ookuma 3 line
at 12:37pm. (1st Cesium adoption apparatus at 3:00 pm, 2nd Cesium
adoption apparatus at 5:00 pm )
- At 10:20 am on November 25, a water leak was detected at the pipe
arrangement between desalination facility and buffer tanks due to the
vent valve open. It is assumed that the valve was opened in the
construction work of attaching lagging material to the pipe.
- At 10:30 am on November 25, a water leakage was detected at the piping
arrangement between water treatment facility and buffer tanks. At 10:57
am, after the water transfer pump was shutdown, the leakage stopped by
conducting a recovery work. At 11:43 am, the pump resumed. After that,
we did a check-up and at 12:45 pm a small amount of water leakage was
detected at other two points. After the recovery work was done and the
leakage stopped at 1:12 pm, the water transfer pump resumed at 2:10 pm.
During that time, we don't think there was any impact on the water
injection into reactor because there was plenty of treated water.
Since the water that run and leaked out from the venting pipe was
already treated in the radioactive and fresh-water terms, we confirmed
the radioactive density of the leaked water was not detectible (below
the measurable limit).
- At 2:54 pm on November 24, we started transferring accumulated water
from Unit 1 T/B to Unit 2 T/B.
