*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.
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 1:31am 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.
- At 3:46 pm on August 17, as we confirmed the decrease in the rate of
water injection to the reactor, we adjusted the rate of water injection
from feed water system piping arrangement at approx. 3.8 m3/h.
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.
Water is currently injected at approx. 9.1 m3/h through reactor feed
water system piping arrangement.
- At 7:38 am on August 18, we switched water injection line to the reactor
from the line which is using a motor driven pump powered by the off-site
transmission line to the line which is using a motor driven pump powered
by emergency diesel generator. At 12:20 pm on the same day, we installed
flow regulating valve to the pipes of water injection line and we switched
water injection line to original line. At 12:27 pm on the same day, we
adjusted the rate of injecting water to the reactor at approx. 8 m3/h.
- Water is currently injected at approx. 8 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.
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. And from 11:06 am to 1:00 pm on August 18, we also
injected hydrazine (corrosion inhibitor).
- At 12:44 pm 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.
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 12:04 pm on August 16, we stopped the operation of water treatment
facility for the combined test of existing facilities and the second
cesium adsorption equipment which was additionally installed. At 2:43 pm
on August 18, we started the operation of the water treatment system.
After that, 3:50 pm on the same day, we stopped the test and resumed
water treatment.
- At 10:00 am, we started transferring accumulated water from the turbine
building of Unit 6 to a temporary tank.
- From approx 2:30 pm on August 18, the instrument reading of transportable
monitoring post became unreadable. After that, on approx 4:00 pm on the
same day, we confirmed the monitoring post indicated normal instrument
reading. We will continue monitoring carefully.
