* 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.
- On 10:30 am on December 23, the changes of injection water flow to
Reactors of Unit 1 was found so we adjusted the water injection from
approx. 1.9 m3/h to 2 m3/h of Core Spray System. (water injection from
feed water system was remained unchanged as approx. 4.5 m3/h).
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.
- 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.
- 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.
- At 6:00 pm on December 19, a full-scale operation of the PCV gas control
system started.
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, in addition to water injection from water
feeding system, we started water injection from piping of core spray
system to the reactor.
On 10:30 am on December 23, the changes of injection water flow to
Reactors of Unit 2 was found so we adjusted the water injection from
approx. 2.5 m3/h to 3 m3/h of Feed Water System Core Spray System.
(water injection from Core Spray System was remained unchanged as approx.
6 m3/h).
The current water injection volume is approx. 3 m3/h from the reactor
feed water system and approx. 6 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 3:03 pm on December 20, we stopped this system due to inspections in
the flow rate detector of the alternative cooling equipment of the Fuel
Pool. This is scheduled to last until around 2:00 pm of December 23 and
during this time we are expecting that the temperature of the spent fuel
pool will rise by 21 °C ( temperature at the time the we stopped the
system: 15.4 °C).
After that, deposits were piled up inside the inlet and outlet pipes of
flow meter when we cut those pipes for inspection. Therefore, we cleaned
up the pipes to remove the deposits. After the completion of the
inspection of the flow meter, at 2:18 pm on December 23, we started the
water injection system and confirmed that there was no fluctuations in
water flow difference (water temperature of spent fuel pool at the time
of system start: 26.6 °C).
- At 8:06 pm on June 28, we started injecting nitrogen gas into the
Primary Containment Vessel.
- At 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.
On 10:30 am on December 23, the changes of injection water flow to
Reactors of Unit 3 was found so we adjusted the water injection from
approx. 6.5 m3/h to 6 m3/h of Core Spray System. (water injection from
feed water system was remained unchanged as approx. 3 m3/h).
The current water injection volume is approx 3 m3/h from the reactor
feed water system and approx. 6 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.
- At around 1 pm on December 22, it was found that the hose of Unit 3
Reactor Water Injection Line was swollen to the extent of 2 meter long.
Although there was no leakage from the swollen hose, it was decided that
the pump for Reactor water injection should be switched from the reactor
injection pump on the hill to the emergency motor pump and the hose
should be replaced with new one.(+) At 7:12 pm on the same day, the
emergency motor pump was started to operate. From 7:44 pm, the valve to
the normal water injection line was closed in order to weep drain from
the line. After the replacement of the hose, at 8:47 pm, the valve to
the normal water injection line was opened to fill water in the line. At
10 pm, it was confirmed that there was no water leakage from the new
hose, so that water injection to the Reactor was adjusted to about
3 m3/hour from Reactor Feed Water System and about 6 m3/hour from
Reactor Core Spray System at about 10:30 pm. At 10:38 pm, the emergency
motor pump was stopped. After that, it was checked that there was no
leakage from the hose and its connection. During the hose replacement
work, the water injection was continued and there was no remarkable
change in temperature of the Reactor Pressure Vessel.
+ Article 12 of Safety Regulation at Nuclear Facilities stipulates
"operational limit" and "required measures if the operational limit is
not satisfied" according to the facility management based on "the
mid-term view point for securing safety". It also stipulates to
respond based on the required measures if the operational limits is
not satisfied. In the case of today's hose swollen, it was regarded to
be sifted off the operational limit as planned (from 6:35 pm on
December 22 to 10:43 pm on the same day) from the proactive
maintenance point of view, so that the hose replacement work was
implemented accordingly.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 2:45 pm on July 15, 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, 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, we started the Residual Heat Removal System
Pump of Unit 6 to cool down Spent Fuel Pool.
- 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 12:25 pm on December 13, we started the re-circulating operation of
desalination facility (reverse osmosis membrane type) for the purpose of
suppression of condensed water after desalination treatment.
- From 1:57 pm on December 21 to 9:42 am on December 23, transfer of a
ccumulated water was implemented from Unit 2 turbine building to the
Centralized Radiation Waste Treatment Facility (Miscellaneous Solid
Waste Volume Reduction Treatment Building [High Temperature Incinerator
Building] and Process Main Building).
- At 10:00 am on December 18, during the patrol activity, a TEPCO employee
found an accumulated water in the trench located between the process
main building of Centralized Radiation Waste Treatment Facility and
Miscellaneous Solid Waste Volume Reduction Treatment Building (High
Temperature Incinerator Building). The depth of the water was estimated
to be 50 cm and the amount was to be 125 m3. The radiation dose at the
water surface was 3 mSv/h (provisional value). As no radioactive
materials have been detected during the last sampling survey of sub
drain water near the trench, the source of the accumulated water is
estimated to be the ground water or dew condensation water.
After that we found water inflow from cable duct near the ceiling of the
trench by detailed survey at site, and we recalculated the amount of the
accumulated water and it was estimated to be approx. 230 m3. And as a
result of the sampling, Cesium-134 was approx. 4.2*103 Bq/cm3,
Cesium-137 was approx. 5.4*103 Bq/cm3 and Iodine-131 was below detection
limit regarding the radioactivity density of the accumulated water in
the trench, and Cesium-134 was approx. 1.3*10-1 Bq/cm3, Cesium-137 was
approx. 1.2*10-1 Bq/cm3 and Iodine-131 was below detection limit
regarding the inflowing water from cable duct. We have conducted water
shut-off treatment of the trench and the groundwater level is higher
than the water level in the trench, therefore we assumed that there is
no possibility of inflow of the accumulated water in the trench to the
groundwater.
Accumulated water in the trench located between the process main
building of Centralized Radiation Waste Treatment Facility and
Miscellaneous Solid Waste Volume Reduction Treatment Building (High
Temperature Incinerator Building) found on December 18 was started to
transfer to Miscellaneous Solid Waste Volume Reduction Treatment
Building (High Temperature Incinerator Building) from 10:19 am on
December 23.
