*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 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
10:02 am on June 22, we changed the rate of water injection to the
reactor from approx. 4.0 m3/h to approx. 3.5m3/h through reactor feed
water system piping arrangement. Water is currently injected at approx.
3.5m3/h through reactor feed water system piping arrangement.
- As it was suspected that hydrogen gas had been accumulated inside Primary
Containment Vessel, in order to prevent increase in density of oxygen,
we commenced the valve opening operation concerning injection of nitrogen
gas into the primary containment vessel at 10:30 pm on April 6 and
commenced injection at 1:31am April 7.
From 11:55 am to 6:05 pm on June 21, we temporarily stopped operating
the nitrogen supply equipment to Unit 1 Primary Containment Vessel due
to work of power supply for alternative cooling equipment of Unit 1
spent fuel pool cooling and filtering system.
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 freshwater by a motor driven pump powered by the
off-site transmission line.
- At 10:04 am on June 22, we changed the rate of water injection to the
reactor from approx. 4.5 m3/h to approx. 4.5m3/h through reactor feed
water system piping arrangement. Afterwards, the rate of water infection
was changed and now became stable at the figure of approx. 3.5m3/h. Water
is currently injected at approx. 3.5m3/h through reactor feed water
system piping arrangement.
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.
At 10:06 am on June 21 we changed the rate of water injection to Unit 3
Reactor from approx. 11 m3/h to approx. 10m3/h through reactor feed water
system piping arrangement. Water is currently injected at approx. 10 m3/h
through reactor feed water system piping arrangement.
Unit 4 (Outage due to regular inspection)
- At approximately 6:00 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 do not consider any reactor coolant leakage inside
the primary containment vessel has occurred.
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
(C) in order to cool the spent fuel pool.
- At 2:30 pm on March 20, the reactor achieved cold shutdown.
- At this moment, we do not consider any reactor coolant leakage inside the
primary containment vessel has occurred.
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
(B) of Unit 6 in order to cool the spent fuel pool.
- At 7:27 pm on March 20, the reactor achieved cold shutdown.
- At this moment, we do not consider any reactor coolant leakage inside the
primary containment vessel has occurred.
Operation for cooling the spent fuel pools
- At 5:21 pm on May 31, we started cyclic cooling of the spent fuel pool
in Unit 2 using alternative cooling system for fuel pool cooling and
filtering system.
- From 2:31 pm to 4:28 pm on June 22, we injected water to Unit 4 through
temporary spraying equipment.
- We will continuously conduct further water spray depending on the
conditions of spent fuel pools, if needed.
Others
- At 1:30 pm on April 26, we started spraying the dust inhibitor inside
the site.
- From 2:00 pm on May 1 to 4:00 pm on June 22, we transferred accumulated
water in the turbine building of Unit 6 to temporary tanks.
- 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 approximately 10:00 am on June 13, we started the operation of the
circulating seawater purification facility installed at the screen area
of Unit 2 and 3.
- From 8:00 pm on June17, we started operation of water treatment of
accumulated water at accumulated water treatment facility. At 12:54 am
on June18, we stopped operation of the facility temporarily due to the
radiation dose at surface level measured up to the basis of exchange
filter of Cesium adsorption Instruments. Afterwards, we exchanged filter
of Cesium absorption Instruments, experimented water flowing and
conducted flashing the facility. From 12:43 am on June 23, the operation
of accumulated water treatment system.
- At 3:32 pm on June 21, we started transferring accumulated water in
turbine building of Unit 3 to central waste treatment facility building.
- At 9:56 am on June 22, we started transferring accumulated water in
turbine building of Unit 2 to central waste treatment facility building.
- From 9:32 am on June 23, we injected fresh water to reactor well and dry
separator pit of Unit 4 for the purpose of environmental improvement
(decreasing dose) at 5th floor of reactor building of Unit 4.
- We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.
