* 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. 4.8 m3/h and that from the core spray system is approx.
1.8 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. 2.9 m3/h and that from the core spray system is approx.
6.1 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. 3.0 m3/h, core spray system: approx. 6.0 m3/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 5:00 am on March 8, the temperature of the lower part of the RPV
(top of the lower head 135°) : approximate 42.4 °C
· At 5:00 am on March 8, the temperature of the lower part of the RPV
(top of the lower head 270°) : approximate 40.3 °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.
- 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 1:25 pm on March 6, 2012, the spent fuel pool desalting facility was
stopped automatically because of an alert caused by increase of water
level of waste water treatment tank. All Isolation valves of desalting
facilities were closed by the interlock, and the alternative cooling
system continues operation. Therefore, there is no influence on cooling.
In addition, as a result of the on-site confirmation, no leakage of
liquid was confirmed. According to our investigation, we confirmed that
the increase of the water level had occurred because of the water
supply to the waste water treatment tank exceeded the drainage volume,
after the treated water by the reverse osmosis membrane unit of the
facility continued to increase because of the purification of the water
supplied to the facility had proceeded. At 4:04 pm on March 7, we
restarted the facility and conducted a test operation, and as there was
no problem, we started regular operation at 5:06 pm on the same day.
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 m3/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 1:55 pm on March 7, 2012, we started the transfer of accumulated
water from the underground of Unit 2 turbine building to the
centralized radiation waste treatment facility process main building.
- At 1:48 pm on March 7, 2012, we started the transfer of accumulated
water from the underground of Unit 3 turbine building to the
centralized radiation waste treatment facility process main building.
