*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.
Water is currently injected at approx. 3.8 m3/h through reactor feed
water system piping arrangement.
-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 1:17 pm on October 26, we started cutting off the designated piping
after confirming that the hydrogen density inside the piping for cooling
in case of reactor shutdown was less than 0.1 %, as one of the
construction work to install gas monitoring system inside the Primary
Containment Vessel. At 3:15 pm on the same day, we finished cutting
pipes. After that, we conducted welding of blind plates of cut pipes and
covering holes of the pipes. At 7:00 pm on the same day, we finished all
operations.
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. 2.9m3/h through reactor feed water
system piping arrangement, and at approx. 7.0 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 8:06 pm on June 28, we started injecting nitrogen gas into the Primary
Containment Vessel.
-At 10:30 am on October 27, we conducted leak test of the system as a part
of construction to settle the gas control system of Primary Containment
Vessel at the reactor building of Unit 2. As a result, we confirmed
in-leak volume to the system had no problem. In addition, we conducted
tentative operation test. As a result, we confirmed operational aspect of
electric heater and exhaust fun had no problem.
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. 2.9 m3/h through reactor feed
water system piping arrangement, and at approx. 8.0 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. (hydrazine injected from 1:30 pm to 3:08 pm)
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 11:34 am on August 20, we started an operation of desalination
equipment in the spent fuel pool.
-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 time, 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 time, we don't think there is any reactor coolant leakage inside
the primary containment vessel.
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.
-At 10:00 am on October 20, we started transferring the accumulated water
from the basement of turbine building of Unit 3 to the High Temperature
Incinerator Building of Central Radioactive Waste Treatment Facility.
-At 10:12 am on October 20, we started transferring the accumulated water
from the basement of turbine building of Unit 2 to the Process Main
Building of Central Radioactive Waste Treatment Facility.
-From 5:31 pm on October 25 to 2:01 pm on October 26, we transferred the
accumulated water brought from the basement of turbine building of Unit 1
to the basement of turbine building of Unit 2.
-From 10:00 am to 4:00 pm on October 26, we transferred the accumulated
water from the basement of turbine building of Unit 6 to the temporary
tanks.
-On October 26, we replaced the hose for transferring reverse osmosis
membrane concentrated water in Water Desalinations (reverse osmosis
membrane) that liquid spoil was found on October 8,
-At 9:47 am on October 26, for the water injection to the reactors of
Units 1 to 3, we switched from normal water injection line to emergency
water injection line, due to the shutoff of facilities for power source
reinforcement work. After that, we switched from emergency water
injection line to normal water injection line due to completion of power
source reinforcement work. (At 4:10 pm on the same day, we confirmed flow
rate stability of Unit 1 and 2. At 3:33 pm on the same day, we confirmed
flow rate stability of Unit 3) Along with the switching work, we adjusted
the amount of water injection from water feeding system to approximately
3.8 m3/h for Unit 1's reactor. For Unit 2, we adjusted the amount of
water injection to the reactor to approximately 3 m3/h from water feeding
system and to approximately 7 m3/h from Core Spray System. Likewise, for
unit 3, we adjusted the amount of water injection to the reactor to
approximately 3 m3/h from water feeding system and to approximately
8 m3/h from Core Spray System.
-At 10:00 am on October 27, we started transferring accumulated water from
the temporary tank to the Mega Float.
-At 9:55 am on October 27, we switched water injection line of unit 1 and
2 from normal water injection line to emergency water injection line to
add the vane to adjust flow amount of water injection line to the Unit
2's reactor in order to improve the ability to control the water
injection amount. At 2:35 pm on the same day, we switched from emergency
water injection line to normal water injection line due to completion of
the work. Injection amount is stable after the work.