*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.
- Since the amount of water injected into the reactor was decreased at
1:49 pm on June 29, we adjust water injection at approx. 3.5 m3/h
through reactor feed water system piping arrangement. Water is currently
injected at approx. 3.5 m3/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 and are now injecting freshwater by a motor driven pump powered
by the off-site transmission line.
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. 3.5 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 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.
- At 2:45 pm on June 29, we started injecting water into Unit 3 using a
temporary motor driven pump.
- 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 9:56 am on June 22, we started transferring accumulated water in
turbine building of Unit 2 to central waste treatment facility building.
- At 4:20 pm on June 27, the operation of circulation injection cooling
was initiated by injecting water from the filter water tank as well as
usage of the treated water regarding water injection to the reactor. At
5:55 pm, since we confirmed a leakage from the pipe which supplies water
from treated water tank to injection pump of reactor, we stopped
supplying treated water. Subsequently, we have implemented measures
against the leakage at pipe joint. At 2:36 pm on June 28, we started
operation of supply pump for treated water, and resumed the operation of
circulation injection cooling at 3:55 pm.
- At around 3:00 pm on June 28, water blot was confirmed at the outlet
flange of the processing transfer pump of the accumulated water
treatment system, and a saucer was installed at 3:45 pm. After that, no
increase of the blot has been confirmed.
- At 8:10 am on June 29, (two) minute holes were confirmed at the hose for
the injection cooling system of the accumulated water treatment system,
and we temporally repaired them. At 10:59 am, we replaced the pipe with
a new one while operation of the processing transfer pump was suspended.
We started to operate circulating injection cooling at 1:33 pm.
- At around 9:30 am on June 29, water leakage was confirmed at the drain
of lower part of the primary storage tank for water desalinations
reverse osmosis membrane concentrated water in the accumulated water
treatment system. We stopped the leakage by installing a drain cap at
10:30 am.
- Since an alarm showing water leakage was sounded in the On-site Bunker
Building at 2:49 pm, the accumulated water treatment system was stopped
at 2:53 pm.
- From 9:40 am to 3:29 pm on June 28, we injected fresh water to the
reactor well (unit 4) and temporally dry separation pool for environment
improvement (reduce radio active dose) on 5th floor reactor building of
unit 4.
- At 12:00 pm on June 28, we found the water level gauge (manometer) of
temporary tank where accumulated water from turbine building in Unit 6
will be transferred lying on the floor. Since accumulated water was
leaking from the gauge, we stopped it by closing main valve. For safety,
we measured surface dose rate around and confirmed the result to be
equivalent to that of surrounding area.
- At around 11:45 am on June 29, while going to the accumulated water
treatment system for inspection, a worker of a partner company was out
of the Main Anti-Earthquake Building, wearing his mask without a filter
for one minute. He returned to the Main Anti-Earthquake Building
immediately after he noticed it. The result of Whole Body Counter
examination suggests that the level of internal radioactivity was
extremely low enough not to affect his body.
- We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.