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. 4.7 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.
-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. 6 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. Through the investigation, we confirmed the
concerned device is soundness. We submitted the report on the soundness
of concerned device and the alternative method for monitoring temperature
inside the Reactor of Unit 2 at Fukushima Daiichi Nuclear Power Station
to NISA on March 1. We continue the observation of the concerned device.
·At 11:00 am on March 12, the temperature of the lower part of the RPV
(top of the lower head 135°) : approximately 42.3 °C
·At 11:00 am on March 12, the temperature of the lower part of the RPV
(top of the lower head 270°) : approximately 40.1 °C (Reference)
-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. In the display for the noble gas monitoring system for
PCV of Unit 2, both A and B system had not worked due to the failure of
the transmission system which connected the site and the Central
Monitoring Station in the Main Anti-Earthquake Building. Because we could
not conduct the monitoring from the monitoring station, we have conducted
remote monitoring by a camera installed at the site since February 20,
2012 for B system and February 21, 2012 for A system. After we revised
software for the transmission system for B system on March 9, 2012 and A
system on March 12, 2012, the monitoring from the Main Anti-Earthquake
Building became available. Since 2:00 pm on the same day, we restarted
data sampling at the Central Monitoring Station in the Main
Anti-Earthquake Building.
-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. 1.8 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 8:47 am on March 11, we started transferring the 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]).
-At 10:10 am of March 10, 2012, we started transferring the accumulated
water from the basement floor of the turbine building of Unit 3 to the
centralized radiation waste treatment facility (Miscellaneous Solid Waste
Volume Reduction Treatment Building [High Temperature Incinerator
Building]).
-At 8:37 am on March 12, 2012, we started transferring the water
accumulated in the site banker building to the process main building in
the centralized waste treatment facilities. At 1:31 pm on the same day,
we stopped transferring.
-At 10:00 am on March 12, 2012, we started transferring the water
accumulated in the basement of Unit 6 Turbine Building to temporary
tanks.
-At around 11:47 am on March 12, 2012, our staff confirmed by over current
alarm of fan motor of compressor at the site, that the nitrogen supply
equipment (nitrogen gas separator A), which supplied nitrogen to the PCVs
and the RPVs of Unit 1-Unit 3, stopped. At 12:09 pm on the same day, we
started the waiting nitrogen supply equipment (nitrogen gas separator B)
and at 12:19 pm, nitrogen injection started again. Regarding the pressure
of PCVs of Unit 1 ? Unit 3 and hydrogen density, we did not confirm any
significant fluctuation (hydrogen density of Unit 3 is monitored as
reference data because the PCV gas control system is now under test
operation).