*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. 1.9 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.
At 10:20 pm on December 11, we stopped the alternative cooling equipment
for spent fuel pool, in order to conduct power source changeover work for
improving power supply reliability. It is scheduled to resume cooling
operation in the afternoon on December 12. The temperature of the pool
was 14 degrees at the time of suspension, and is estimated to rise for
approx. 3 degrees due to the suspension.
-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.
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, we started injecting water to the reactor
through core spray system water injection piping arrangement in addition
to the water injection through reactor feed water system piping
arrangement.
The current water injection volume is approx 2.7 m3/h from the reactor
feed water system and approx. 6.1 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 8:06 pm on June 28, we started injecting nitrogen gas into the Primary
Containment Vessel.
-From 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 2.9 m3/h from the reactor
feed water system and approx. 5.9 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 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 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 2:30 pm on March 20, the reactor achieved cold shutdown.
-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 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 7:27 pm on March 20, the reactor achieved cold shutdown.
-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.
-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.
-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 6:03 pm on November 30, we started transfer of the accumulated water
from the basement of Unit 2 turbine building to Centralized Radiation
Waste Treatment Facility High Temperature Incinerator Building.
-At 3:48 pm on December 11, we confirmed that the water was accumulated
inside the gate in the house where the water desalination equipment
(evaporative concentration equipment) 2 was installed. The amount of the
leaked water is approx. 5 litters, and the water was kept within the gate.
We also confirmed that the leakage has been stopped, and that it was
leaked from a ventilation pipe at the tank storing the seal water for the
evaporative concentration equipment 2B. The source of the water is the
filtered water (fresh water), and the radiation doses of the surface near
the leaked water are 0.12 mSv/h (gamma ray), and less than 1 mSv/h (beta
ray), which are the same level as the airborne radiation doses nearby. We
will investigate the cause. Since water desalination equipment (reverse
osmosis membrane equipment) 2-1 and 2-2 are continuously working, which
generate the sufficient amount of desalinated water, there is no impact
on the water injection to the reactors. At approx. 11:00 am on December
12, we confirmed that the remaining water in the hose was oozing from the
leakage point (the leakage amount is about 1 drop in 3 seconds). Later we
removed the water from the tank for the seal water and from the hose. At
approx. 3:00 pm on the same day, we confirmed that the water ceased to
ooze.
-At 10:00 am on December 12, we started transferring of accumulated water
from the Turbine Building of Unit 6 to the temporary tank.
-When we cut the power of the PCV gas control system (Line A: under
suspension) of Unit 1 to switch the power source for the improvement work
of the on-site power source at approx. 10:38 am on December 12, the
monitoring system in the main anti-earthquake building for the same
system (Line B: under commissioning) was stopped. At approx. 11:30 am, we
confirmed on site that the system (Line B) was stopped. Later, it was
revealed that the power for controlling Line B comes from Line A,
therefore we switched the power for the control, then at 12:00 pm we
resumed Line B. Since Line B is normally operating after the re-start, we
estimate that the reason Line B went down is that the power for Line A
was cut.
