*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 10:11 am on December 10, 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 volume is approx. 4.4 m3/h from the reactor
feed water system and approx. 2 m3/h from the core spray 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.
- At 4:04 pm on November 30, we started operation to inject nitrogen into
the reactor pressure vessel.
- At 6:00 pm on December 19, a full-scale operation of the PCV gas
management system started.
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, in addition to water injection from water
feeding system, we started water injection from piping of core spray
system to the reactor.
At 11:00 am on December 27, regarding the water injection into the
reactor core of unit 2, for the purpose of preparation of commissioning
of water injection pumps for diversification, water injection rate from
feed water system was adjusted from approx. 2.8 m3/h to 2.0 m3/h, from
core spraying system was adjusted from approx. 6.0 m3/h to 7.0 m3/h.
The current water injection volume is approx. 2.0 m3/h from the reactor
feed water system and approx. 7.0 m3/h from the core spray system.
- 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 1:36 pm to 3:12 pm on December 26, we
also started to inject hydrazine [corrosion inhibitor]).
At 1:58 pm on December 27, in the alternative cooling system of the spent
fuel pool of Unit 2, as the inhale pressure of the primary circulating
pump showed the tendency of decrease, we stopped the pump in order to
conduct flushing of the strainer on its entry side and suspended cooling
of the spent fuel pool (the temperature of the pool at the time of the
suspension was approx. 14.2°C). Expected temperature increase will be
approx. 0.3°C/h (suspension period will be approx. 1 hour) and there is
no concern to the water temperature of the spent fuel pool.
- At 8:06 pm on June 28, we started injecting nitrogen gas into the Primary
Containment Vessel.
- At 6:00 pm on October 28, we put the gas management system of the reactor
containment vessel in operation.
- At 10:46 am on December 1, we started the nitrogen injection to the
Reactor Pressure Vessel.
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.
The current water injection volume is approx 3 m3/h from the reactor feed
water system and approx. 6 m3/h from the core spray system.
- 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 2:00 pm on December 26, in the alternative cooling system of the spent
fuel pool, as the inhale pressure of the primary circulating pump showed
the tendency of decrease, we stopped the pump in order to conduct
flushing of the strainer on its entry side and suspended cooling the
spent fuel pool (the temperature of the pool at the time of the
suspension was approx. 13°C). After flashing, as inhale pressure of the
pump has recovered, at 4:32 pm on the same day, the pump was restarted
and cooling of spent fuel pool was restarted (the temperature of the pool
at the time of restart was approx. 13°C).
- At 8:01 pm on July 14, injection of nitrogen gas into the Primary
Containment Vessel started.
- At 4:26 pm on November 30, we started operation to inject nitrogen into
the reactor pressure vessel.
Unit 4 (Outage due to regular inspection)
- At around 6:00 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.
- At 10:58 am on November 29, 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, we started the Residual Heat Removal System Pump
in order to cool the spent fuel pool.
- 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 10:11 am on December 22, 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, we started the Residual Heat Removal System Pump
of Unit 6 to cool down Spent Fuel Pool.
- 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.
- Due to the completion of restoration of residual heat recovery (RHR) sea
water pump (A) of unit 6, which was not be able to use by the affect of
tsunami, at 10:19 am on December 27, commissioning was started, at 11:30
am as no incident was observed, it returned to usual operation. As a
result, two RHR pumps, (A) and (C), had been returned to service. During
the commissioning, while RHR pump (A) of unit 6 was temporary stopped
from 10:01 am to 11:09 am and cooling of reactor core was suspended, as
the increase of core water was approx. 0.7°C and there were no concerns
to the safety.
- 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.
The second Cesium adsorption apparatus, which has been shut down since
8:44 am on December 12, restarted at 10:37 am on December 27. Treatment
of accumulated water restarted which has been suspended since December 20.
- 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 12:25 pm on December 13, we started the re-circulating operation of
desalination facility (reverse osmosis membrane type) for the purpose of
suppression of condensed water after desalination treatment.
- From 10 am to 4 pm on December 26, we transferred accumulated water from
the Turbine Building of Unit 6 to the temporary tank.
- From 10:10 am on December 26 to 9:54 am on December 27, we transferred
accumulated water from the basement of turbine building of Unit 2 to the
Centralized Radiation Waste Treatment Facility (Miscellaneous Solid Waste
Volume Reduction Treatment Building [High Temperature Incinerator
Building] and the Process Main Building).
- On December 26, two of TEPCO's employee who were engaged in recovery
work at Fukushima Daiichi Nuclear Power Station was diagnosed as
influenza. On December 27, one TEPCO's employee who was also engaged in
recovery work at Fukushima Daiichi Stabilization Center was newly
diagnosed as influenza. We will take countermeasure for infection and
escalation prevention by promoting hand washing, gargle, finger
disinfecting and cough etiquette and will endeavor to set and use
thermometer, finger disinfecting alcohol, mask.
- At 10:14 am on December 27, we started transfer of accumulated water from
site banker to process main building in the centralized radiation waste
treatment facility.
