*New items 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 approximately 2:30 am on March 23, seawater injection to the reactor
through the reactor feed water system was initiated.
- From 3:37 pm on March 25, we started injecting freshwater by a motor
driven pump which is now powered by the off-site transmission line.
- At 3:52 am on August 12, as we observed decline in the volume of water
injected into the reactor through reactor feed water system piping
arrangement.
Water is currently injected at approx. 3.9 m3/h through reactor feed
water system piping arrangement.
- We commenced injection of nitrogen gas into Primary Containment Vessel
at 1:31am on April 7.
- At 9:00 am on August 10, we started to assemble steel frame for the
Reactor Building Cover.
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.
- From 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.
Water is currently injected at approx. 3.8 m3/h through reactor feed
water system piping arrangement.
- At 8:06 pm on June 28, we started injecting nitrogen gas into the Primary
Containment Vessel.
Unit 3 (Shut down)
- Explosive sound and white smoke were confirmed at approximately 11:01am
on March 14. It was assumed to be hydrogen explosion.
- From 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. However at 4:22 pm on August 10, we adjusted
the flow rate of injection water to the reactor.
Water is currently injected at approx. 9.1 m3/h through reactor feed water
system piping arrangement.
- At 8:01 pm on July 14, injection of nitrogen gas into the Primary
Containment Vessel started.
Unit 4 (Outage due to regular inspection)
- At approximately 6 am on March 15, we confirmed the explosive sound and
the sustained damage around the 5th floor rooftop area of Reactor Building.
- 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 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 Pump (B).
- 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 this time, we don't think there is any reactor coolant leakage inside
the primary containment vessel.
- From 9:30 am to 1:40 pm on August 9, we conducted plumbing between
temporary pump and residual heat removal system pump (A) to enforce the
connection method. We stopped the power source of residual heat removal
system pump (B) during this work. Even though cooling of a reactor and a
spent fuel pool were temporarily suspended, there are no safety issues
regarding this.
Operation for cooling the Spent Fuel Pools
- At 5:21 pm on May 31, we started cyclic cooling of Spent Fuel Pool of
Unit 2 by using alternative cooling system of the Pool's cooling and
filtering system.
- At 7:47 pm on June 30, we started cyclic cooling of Spent Fuel Pool of
Unit 3 by using alternative cooling system of the Pool's cooling and
filtering system.
- At 0:44 am on July 31, we started cyclic cooling of Spent Fuel Pool of
Unit 4 by using alternative cooling system of the Pool's cooling and
filtering system.
- At 11:22 am on Aug 10, we started cyclic cooling of Spent Fuel Pool of
Unit 1 by using alternative cooling system of the Pool's cooling and
filtering system.
Injured
- Around 12:05 pm on August 10, one partner company worker who was mowing
for curing of water treatment hose at west side of Centralized Radiation
Waste Treatment Facility (outside) was injured his right leg by sickle
and was transferred to the Fukushima Rosai Hospital by the ambulance.
Diagnose was given as contusion of right leg.
Others
- At 11:00 am on May 10, we started transferring accumulated water from
the underground level of reactor building to the radiation waste treatment
facility of Unit 6.
- 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 8:00 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 8:42 am on August 5, we started transferring accumulated water at
Unit 3 turbine building to Centralized Radiation Waste Treatment Facility.
- At 10:00 am on August 9, we started transferring low level accumulated
water from outdoor temporary tanks to Mega Float. However, at 10:12 am,
since leakage was confirmed from the transferring pipes cabled at outside,
we stopped transferring. Thereafter, such pipes were replaced and at 1:35
pm, we resumed transferring.
- At 11:00 am on August 9, we started transferring of accumulated water
from inside the Unit 6 turbine building to temporary tanks and finished
on 5:00 pm on August 10.
- At 4:47 pm on August 10, we started transferring of accumulated water
from turbine building of unit 2 to Centralized Radiation Waste Treatment
Facility.
- From 10:00 am to 4:00 pm on August 11, we transferred accumulated water
from inside the Unit 6 turbine building to temporary tanks. At 10:00 am
on August 12, we restarted transferring accumulated water.
- At around 3:00 pm on August 11, we confirmed opening the breaker which
supply power to the battery charger of the power source for controlling
the temporary metal clad of Units 1 and 2. At 4:00 pm, we observed decline
in the voltage of the back-up battery of the power source for controlling,
at 1:21 pm on August 12, we replaced the battery and the battery charger
and restarted receiving power.
- At around 3:22 on August 12, a 6-magnitude earthquake centered in off the
coast of Fukushima prefecture occurred. There were no abnormalities
observed in the status of water injection into the reactors of Units 1 to
3, nitrogen gas injection into the primary containment vessels of Units
1 to 3, operation of water treatment facilities, circulating cooling of
pool water by the substitute pool cooling and filtering system, etc.
There was no influence on the operation of water treatment system,
however, the boiler of concentrating device of the desalination instrument
stopped and we reset it at 3:42 pm. Later during a patrol, there was no
influence found on the important facilities, however, at 5:06 am, we found
one of the two temporary air compressors for instrumentation stopped. As
we could not restart it, we started a back-up diesel-powered compressor
at 6:44 am. At 5:27 am, we observed a slight amount of bleeding at the
surface of a hose of a spent fuel pool circulating cooling facility in the
waste treatment building of Unit 4. We are planning to replace it later.
There is neither abnormality in the major parameters of each unit, nor
injuries to the staff. The readings of the monitoring posts stay in the
normal fluctuation range.
