*The 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, 2011. It was assumed to be hydrogen
explosion.
- At 3:37 pm on March 25, 2011, 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 10:11 am on December 10, 2011, in addition to water injection from
water feeding system, we started water injection from piping of core
spray system to the reactor.
The current water injection amount from the reactor feed water system is
approx.4.6 m3/h and that from the core spray system is approx. 2 m3/h.
- At 1:31 am on April 7, 2011, we commenced injection of nitrogen gas into
Primary Containment Vessel.
- At 11:22 am on August 10, 2011, 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, 2011, we completed installation of the cover for the
Reactor Building in order to contain dispersion of radioactive
substances.
- At 4:04 pm on November 30, 2011, we started operation to inject nitrogen
into the reactor pressure vessel.
- At 6:00 pm on December 19, 2011, a full-scale operation of the PCV gas
management system started.
Unit 2 (Shut down)
- At approximately 6:00 am on March 15, 2011, an abnormal noise began
emanating from nearby Pressure Suppression Chamber and the pressure
within the chamber decreased.
- At 10:10 am on March 26, 2011, 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, 2011, in addition to water injection from
feed water system, we started water injection from piping of core spray
system to the reactor.
To improve reliability of water injection to the reactors, the injection
line connecting to the reactor injection pump on the hill was replaced
with polyethylene pipes and we have been changing the route for reactor
injection from feed water system to reactor core spray system in a
stepwise manner. After completion of adjusting water flow amount as
planned on February 2, tendency of temperature rise at the bottom of PCV
was observed. Thus, at 7:20 pm on February 3, 2012, we changed the
injection amount into Unit 2 reactor through feed water system from
approx. 2.9 m3/h to approx. 4.9 m3/h and changed that though reactor
core spray system from approx. 5.8 m3/h to approx. 3.8 m3/h (which means
setting them at those of before flow adjustment on February 1, 2012).
After that, we have observed the tendency of temperature at the upper
head of the bottom of PCV. Because we found the temperature has risen
again (approximate 66.1 °C at 11:00 pm on February 4), at 12:52 am on
February 5, we changed the water injection volume to Unit 2 reactor
through the feed water system from approx. 4.8 m3/h to approx. 5.8 m3/h
(the water injection through the reactor core spray system remains
approx. 3.8 m3/h). At this moment, the temperature indicates 67.4 °C (as
of 5:00 am on February 5). we will monitor it continuously.
The current water injection amount from the reactor feed water system is
approx.5.8 m3/h and that from the core spray system is approx. 3.8 m3/h.
- At 5:21 pm on May 31, 2011, 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, 2011, we started injecting nitrogen gas into the
Primary Containment Vessel.
- At 6:00 pm on October 28, 2011, a full-scale operation of the PCV gas
management system started.
- At 10:46 am on December 1, 2011, we started the nitrogen injection to
the Reactor Pressure Vessel.
- At 11:50 am on January 19, 2012, we started the operation of the spent
fuel pool desalting facility.
At 10:56 pm on February 4, "Abnormal state (low pressures) in suction
pressure of RO high pressure pump" triggered the alarm in the desalting
facility for spent fuel pool of Unit 2, and the facility automatically
stopped. Because all isolation valves of the system have been closed due
to the interlock and the alternative cooling system for spent fuel pool
is continuously operated, it does not affect the cooling for the spent
fuel pool. In addition, as a result of site check, it was confirmed that
any leakage from the facility was not found. The cause is now under
investigation.
Unit 3 (Shut down)
- Explosive sound and white smoke were confirmed at approximately 11:01 am
on March 14, 2011. It was assumed to be hydrogen explosion.
- At 6:02 pm on March 25, 2011, 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, 2011, we started water injection by core
spray system in addition to water injection by the reactor feed water
system piping arrangement.
The current water injection amount from the reactor feed water system is
approx. 3m3/h and that from the core spray system is approx. 6m3/h.
- At 7:47 pm on June 30, 2011, 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 1:24 pm to 3:07 pm on February 3,
2012, we injected hydrazine [corrosion inhibitor].)
- At 8:01 pm on July 14, 2011, injection of nitrogen gas into the Primary
Containment Vessel started.
- At 4:26 pm on November 30, 2011, we started operation to inject nitrogen
into the reactor pressure vessel.
- At 3:18 pm on January 14, we started operation of the radioactive
material removal instrument for the spent fuel pool in Unit 3
Unit 4 (Outage due to regular inspection)
- At around 6 am on March 15, 2011, 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, 2011, 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 10:58 am on November 29, 2011, in order to decrease more salinity, we
installed Ion exchange equipment and started the operation of such
equipment.
- 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, 2011, we started the Residual Heat Removal
System Pump in order to cool the spent fuel pool.
- At 2:45 pm on July 15, 2011, we started the operation of the original
Residual Heat Removal System (System B) by its original seawater pump.
- At 10:11 am on December 22, 2011, since we finished the recovery work of
seawater pump (System B) of equipment water cooling system, we made a
trial run. At 11:25 am on the same day, we confirmed no abnormalities
and restarted the operation.
- 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, 2011, we started the Residual Heat Removal
System Pump of Unit 6 to cool down Spent Fuel Pool.
- At 2:33 pm on September 15, 2011, 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 10:00 am on June 13, 2011, 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, 2011, 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, 2011, 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, 2011, 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, 2011, 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 12:25 pm on December 13, 2011, we started the re-circulating
operation of desalination facility (reverse osmosis membrane type) for
the purpose of suppression of condensed water after desalination
treatment.
- As finding of accumulated water containing radioactive materials at the
trench between the Process Main Building and the Miscellaneous Solid
Waste Volume Reduction Treatment Building [High Temperature Incinerator
Building] (December 18, 2011), we started the inspection of other
trenches at the site on January 11.
- At 4:07 pm on February 3, 2012, we started to transfer accumulated water
from the basement of T/B, Unit 2 to the Centralized Waste Treatment
Facility (Miscellaneous Solid Waste Volume Reduction Treatment Building
[High Temperature Incinerator Building] and Process Main Building).
- At 9:18 am on January 31, we started transfer of Sub-drain Water of Unit
6 to the temporary tank. We will conduct transferring to the temporary
tank appropriately.
- At about 7:10 pm on February 4, a worker of a partner company which
operated the water desalinations said he was in bad shape. He was
examined and treated at the emergency medical clinic of Unit 5&6 and
judged that he required an emergency transfer. Then he was transferred
to the J Village at 9:06 pm. After that, at 9:50 pm, he was transferred
to Iwaki Kyouritsu Hospital from the J Village. At this moment, the
doctors examine and treat. The patient does not have any radiation
materials.
- At 9:49 am on February 5, we started water transfer from the basement of
turbine building of Unit 3 to Centralized Radiation Waste Treatment
Facility (Miscellaneous Solid Waste Volume Reduction Treatment Building
[High Temperature Incinerator Building]).
