*The 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, 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 volume is approx. 4.5 m3/h from the reactor
feed water system and approx. 2 m3/h from the core spray system.
- 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
water feeding system, we started water injection from piping of core
spray system to the reactor.
- At 5:10 pm on January 25, regarding the reactor injection from the feed
water system at the Unit 2, we changed the injection line from the pump
located uphill to the T/B reactor injecting pump.
The current water injection amount from the reactor feed water system
is approx. 7 m3/h and that from the core spray system is approx. 1.8 m3/h.
- 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-scale operation of the PCV gas
management 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.
- At 3:01 pm on January 27, the water injection to the reactor from the
feed water injection system was switched from the reactor water
injection pump in the turbine building to the reactor water injection
pump on the hill.
At 2:02 pm on January 28, the volume from the feed water system
decreased from approx. 8 m3/h to approx. 7 m3/h, and the volume from
reactor core spray system increased from approx. 0.5 m3/h to approx.
2 m3/h.
The current water injection amount from the reactor feed water system
is approx. 7 m3/h and that from the core spray system is approx. 2 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.
- At 4:26 pm on November 30, 2011, we started operation to inject
nitrogen into the reactor pressure vessel.
- At 3:18 pm on January 14, we started operation of the radioactive
material removal instrument for the spent fuel pool in Unit 3
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.
- 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, 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.
- At this moment, we do not think there is any reactor coolant leakage
inside PCV.
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.
- As finding of accumulated water containing radioactive materials at the
trench between the Process Main Building and the Miscellaneous Solid
Waste Volume Reduction Treatment Building [High Temperature Incinerator
Building] (December 18, 2011), we started the inspection of other
trenches at the site on January 11.
- At 10 :00 am on January 28, we started to transfer the accumulated
water from the basement of T/B, Unit 6 to the temporary tank.
- At 10:29 am on January 28, when a TEPCO worker checked the reactor
water injection system, he found water leakage from the Vent Valve
around the Normal Reactor Injection Pump (B) on the Hill which was on
standby. At around 10:36 am, we closed the anterior and posterior valve
of the pump and at around 11:19 am, we checked that the leakage was
stopped. (We estimated the amount of leakage was approx. 9 liters.) The
water did not flow out to the sea because there was no drain there. We
also checked that the surface dose rate around the leakage point was
the same level of the atmosphere dose rate. Currently, we are checking
the similar places. We will conduct a detail inspection to find the
reason of the leakage and take countermeasures. We continue to inject
water to the reactor from the Normal Reactor Injection Pump on the Hill
(A) and (C).
- At 12:00 pm on January 28, when a TEPCO worker checked the water
treatment facility, he found water was leaked around a drop per second
from the Valve Flange around the Demineralizer of the Evaporation
Concentration Apparatus. (We estimated the amount of leakage was approx.
8 liters.) The water did not flow out to the sea because it was in the
weir tank. We also checked that the surface dose rate around the
leakage point was the same level of the atmosphere dose rate. Currently,
we took countermeasure to receive leaked water by pan. This facility is
now suspended. As there is sufficient desalinated water, we continue
the operation of the water treatment facility and the injection to the
reactor.
- At 12:00 pm on January 28, when a TEPCO worker checked the water
treatment facility, he found water was leaked around a drop per 5
seconds from the Valve Flange of Mini Flow Piping of the Waste RO*
Supply Pump where the treated water is sent from the suppression pool
water surge-tank to the water desalinations. (The amount of leakage was
approx. 0.5 liters.) The water did not flow out to the sea because it
was in the weir tank. We also checked that the surface dose rate around
the leakage point was the same level of the atmosphere dose rate.
Currently, we took countermeasure to receive leaked water by pan. The 2
RO Supply Pumps are now on stand-by and we continue the operation of
the water treatment facility and the injection to the reactor.
* RO: Reverse Osmosis Membrane
