*Updates from previous press release 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. 3.4m3/h through reactor feed water
system piping arrangement.
- We commenced injection of nitrogen gas into Primary Containment Vessel
at 1:31am April 7.
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.
At 6:27 pm on June 23, we changed the water injection line so that we can
inject water to Unit 1 and 2 by the motor driven pump for Unit 1 and
stopped the motor driven pump for Unit 2.
Water is currently injected at approx. 3.5m3/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. 9m3/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.
- At 7:47 pm on June 30, we started cyclic cooling of the spent fuel pool
in Unit 3 using alternative cooling system for fuel pool cooling and
filtering system.
- 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.
- 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 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 3:15 pm on July 10, we started transferring the accumulated water from
the turbine building of Unit 3 to Centralized Radiation Waste Treatment
Facility Process Main Building.
- At 8:51 am on July 12, we found some leakage around the connection part
at the liquid chemical injection line of coagulation setting devices in
accumulated water treatment facilities and therefore stopped the
operation of the facilities. Afterward, we repaired the leakage part at
4:19 pm, started operation of the accumulated water treatment facilities
at 4:28 pm and resumed the accumulated water treatment at 4:58 pm. Also
water injection to the reactor has been carried on during this time.
- From 11:00 am to 4:00 pm on July 12, we transferred low radioactive
accumulate water in the outside temporary tanks to the Mega Float.
- At 11:22 on July 12, in order to reduce radiation level on the 5th floor
of the reactor building of Unit 4, we started fresh water injection to
the reactor well and the pool to put equipment temporarily. However we
found water leakage from injection water line and stopped the injection
on 12:03 on the same day. As a result of survey, we found water leakage
from a connection part with water hose. Today we will restart the water
injection after changing the hose.
- As a countermeasure against seawater leakage from the piping of the
outside temporary residual heat removal seawater system of the residual
heat removal system of the Unit 5 occurred on July 3, we bound the piping
tightly. However we found the similar part after reconfirmation of the
site, in terms of preventive maintenance, we stopped the residual heat
removal system at 6:30 am on July 13, stopped outside temporary seawater
cooling pump at 6:44 am, and then started the piping replacement.
- At 10:00 am on July 13, we started transferring low radioactive
accumulate water in the outside temporary tanks to the Mega Float.
- We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.