*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.
The current water injection volume is approx 4.3m3/h from the reactor
feed water system.
- We commenced injection of nitrogen gas into Primary Containment Vessel
at 1:31 am on April 7.
- In order to construct the nitrogen injection line direct to the reactor
branched by the nitrogen injection line into the primary containment
vessel of Unit 1, at 11:40 am on November 30, we temporarily stopped
Nitrogen injection into the primary containment vessel. Then, we
restarted Nitrogen injection into the primary containment vessel. At
12:23 pm on the same day, we confirmed the nitrogen injection amount
(28m3/h) into the primary containment vessel was stable.
- 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.
- On October 28, we completed installation of the cover for the Reactor
Building in order to contain dispersion of radioactive substances.
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.
Water is currently injected at approx. 3.1m3/h through reactor feed water
system piping arrangement, and at approx. 4.4 m3/h through core spray
system water injection piping arrangement.
- 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 1:26 pm on November 30, we started
injection of hydrazine).
- 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 11:04 am on November 6, we started operation of radioactive material
decontamination instrument of spent fuel pool.
- On November 29, sampling survey of gas at the gas management system of
Unit 2 primary containment vessel was implemented. As a result of the
analysis, we regarded the situation was not erratically because the
radioactive density at the gas management system of Unit 2 primary
containment vessel was under ND (1.1x10-1Bq/cm3), the criteria of
erratically is 1 Bq/cc. Regarding Xe-135, its radioactive density was
detected by charcoal filter* (we regarded spontaneous fission). According
to the Report with regard to "Policy on the mid term security" for the
Units 1 to 4 of Fukushima Daiichi Nuclear Power Station to Nuclear and
Industrial Safety Agency at the Ministry of Economy, Trade and Industry
(1) (revision) (for public on November 9), the situation of erratically
therefore should be regarded by the sampling survey of gas at the gas
management system of Unit 2 primary containment vessel by vial.
* Detection Limit Charcoal filter: 10-6 level, Vial: 10-1 level
- At 1:45 pm on November 30, we started nitrogen injection to the Reactor
Pressure Vessel. At 2:47 on the same day, as we confirmed nitrogen
injection had not increased, we temporally stopped the operation. The
cause is under investigation. We are continuing nitrogen injection into
the primary containment 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.
Water is currently injected at approx. 2.1 m3/h through reactor feed
water system piping arrangement, and at approx. 6.0 m3/h through core
spray system water injection piping arrangement.
- 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.
- In order to construct the nitrogen injection line direct to the reactor
branched by the nitrogen injection line into the primary containment
vessel of Unit 3, at 11:33 am on November 30, we temporarily stopped
Nitrogen injection into the primary containment vessel. Then, we
restarted Nitrogen injection into the primary containment vessel. At
1:20 pm on the same day, we confirmed the nitrogen injection amount
(28m3/h) into the primary containment vessel was stable.
- At 9:00 am on November 30, we started dust sampling above the reactor
building of Unit 3 with a large crane. At 12:30 pm on the same day, we
finished the sampling.
- At 10:00 am on November 30, we started dust sampling by a robot near the
equipment hatch of ground floor, reactor building unit 3. At 10:30 am on
the same day, we finished sampling.
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.
- Regarding spent fuel pool for unit 4, from August 20 to November 8, we
had decreased salinity by using the desalting facility. In order to
decrease more salinity, we installed Ion exchange equipment and started
the equipment at 10:58 am on November 29.
- 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.
- From November 28, we started cleaning to avoid the performance
deterioration of pumps by sucking up sands etc. accumulated at the
bottom of the inlet canal pump room.
- 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 9:25 am on November 15, we started transfer of accumulated water from
basement of Unit 3 turbine building to Centralized Radiation Waste
Treatment Facility Building.
