*Updates from previous press release 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.1.7 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.
The current water injection amount from the reactor feed water system is
approx.2.8 m3/h and that from the core spray system is approx.5.8 m3/h.
-With regard to the water injection volume for Unit 2 reactor, which was
increased with temperature figure raising, we have gradually adjusted it
to the original volume before temperature increasing (Feed water system:
approx. 3.0m3/h, core spray system: approx. 6.0m3/h). During our
observing the plant parameter after decreasing the flow rate of feed
water system on February 22, we found that one thermometer in the lower
part of the RPV (top of the lower head 135°) indicated the different
movement from others. From 12:21 pm to 2:48 pm on February 23, we
investigated the concerned device. As the result of the measurement of DC
resistance, we found no breaking wire and availability of the thermometer.
But we confirmed that the DC resistance of it became higher than the
previous measurement test data. We will evaluate the soundness of the
concerned device and examine correspondence in future. We make sure no
re-criticality state because there were no significant changes at the
monitoring post and as the result of the sampling for the Gas Control
System of the Unit 2; we confirmed that the concentration of Xe-135 was
below the detectible limit.
·At 5:00 am on March 2, the temperature of the lower part of the RPV
(top of the lower head 135°) : approximate 44.7 °C
(Reference)
·At 5:00 am on March 2, the temperature of the lower part of the RPV
(top of the lower head 270°) : approximate 41.4 °C
-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 operation of the PCV gas control
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.
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.1.7 m3/h and that from the core spray system is approx.5.2m3/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.
-At 8:01 pm on July 14, 2011, injection of nitrogen gas into the Primary
Containment Vessel started.
-As installation works of the PCV gas control system was completed, we
started a test operation at 11:38 am on February 23, 2012. We confirmed
that an exhaust flow amount was stable at 33Nm3/h at 2:10 pm and started
an adjustment operation.
-At 4:26 pm on November 30, 2011, we started operation to inject nitrogen
into the reactor pressure vessel.
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.
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.
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.
-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 1:56 pm on February 28, we started transfer the accumulated water from
the basement of turbine building of Unit 3 to Miscellaneous Solid Waste
Volume Reduction Treatment Building (High Temperature Incinerator
Building).
-At 2:00 pm on February 28, we started transferring accumulated water from
basement of unit 2 turbine building to Centralized Radiation Waste
Treatment Facility Process Main building.
-From 10:00 am to 4:00 pm on March 1, we transferred the accumulated water
from the basement of T/B, Unit 6 to the temporary tanks.
-From 8:26 am to 3:18 pm on March 1, as we confirmed that high
radioactivity contaminated water is accumulating in the pit of the water
circulating pump discharge valve of unit 3 pump chamber at the inspection
of trench etc. conducted on January 19, 2012, we transferred the
accumulated water from the pit to the basement of unit 2 turbine building.
-In order to conduct the work to improve the reliability of water
treatment facilities, we are planning to stop water treatment facilities
one after another. At 8:45 am on March 1, we stopped the cesium
adsorption apparatus. It will be out of service until March 15. We
calculated the estimated water level increase at each building due to the
stop o the facilities, and confirmed that the water levels in each
building will be maintained within the limits. We also have sufficient
volume of treated water, therefore there will be no impact on the water
injection to the reactors. At 8:07 am on March 2, we stopped the 2nd
Cesium Adsorption Apparatus.
-At 9:44 am on March 2, in order to conduct the work to switch the control
circuits of on-site power source for operation of southern switching
station, we cut the power of on-site power source. The evaporation
apparatuses of water desalination facilities and desalination facilities
(reverse osmosis membrane type) are out of service due to the work to
switch the control circuits. We also have sufficient volume of treated
water, therefore there will be no impact on the water injection to the
reactors.
