*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 12th. It was assumed to be hydrogen
explosion.
-At approximately 2:30 am on March 23rd, seawater injection to the nuclear
reactor through the feed water system was initiated.
-From 3:37 pm on March 25th, we started injecting freshwater and are now
injecting fresh water by a motor driven pump powered by the
off-site transmission line.
-As it is suspected that hydrogen gas is accumulated inside reactor
containment vessel, we commenced the valve opening operation concerning
injection of nitrogen gas into the reactor container vessel at 10:30 pm
April 6th and commenced injection at 1:31am April 7th.
Unit 2(Shut down)
-At approximately 6:00 am on March 15th, an abnormal noise began emanating
from nearby Pressure Suppression Chamber and the pressure within the
chamber decreased.
-From 10:10 am on March 26th, 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.
Unit 3(Shut down)
-Explosive sound and white smoke were confirmed at approximately 11:01am
on March 14th. It was assumed to be hydrogen explosion.
-From 6:02 pm on March 25th, 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.
Unit 4(outage due to regular inspection)
-At approximately 6:00 am on March 15th, we confirmed the explosive sound
and the sustained damage around the 5th floor rooftop area of the Nuclear
Reactor Building.
-At this moment, we do not consider any reactor coolant leakage inside the
reactor happened.
Unit 5(outage due to regular inspection)
-Sufficient level of reactor coolant to ensure safety is maintained.
-At 5:00 am on March 19th, we started the Residual Heat Removal System
Pump (C) in order to cool the spent fuel pool.
-At 2:30 pm on March 20th, the reactor achieved reactor cold shutdown.
-At this moment, we do not consider any reactor coolant leakage inside the
reactor happened.
Unit 6(outage due to regular inspection)
-Sufficient level of reactor coolant to ensure safety is maintained.
-At 10:14 pm on March 19th, 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 20th, the reactor achieved reactor cold shutdown.
-At this moment, we do not consider any reactor coolant leakage inside the
reactor happened.
Operation for cooling the spent fuel pools
-From 3:55 pm to 5:40 pm, April 22nd, fresh water was injected into Unit 2
by the temporary motor driven pump.
-From 5:52 pm to 11:53 pm, April 22nd, water was sprayed to the spent fuel
pool of Unit 4 by the concrete pumping vehicle.
-We will conduct further water spray depending on the conditions of spent
fuel pools, if needed.
Others
-The national government has instructed evacuation for those local
residents within 20km radius of the periphery and shelter in place for
those residents from 20km to 30km radius of the periphery, because it is
possible that radioactive materials are discharged.
-At 10:08 am on April 19th we started transferring high level radioactive
wastewater to the Centralized Radiation Waste Treatment Facility.
-From 11:30am to 2:00pm, we opened and closed the double doors and
conducted surveys of the situation of the inside of the nuclear reactor
building of Unit 3 and measured a dose of radiation, etc. by a remote
control robot. Also, from 4:00pm to 5:30pm, we did the same kind of work
on Unit 1. From 1:42pm to 2:33pm on April 18th, we opened and closed the
double doors, measured a dose of radiation and so on, and conducted
surveys of the situation of the inside of the nuclear reactor building of
Unit 2, by a remote control robot.
-We will continue to take all measures to ensure the safety and to
continue monitoring the surrounding environment around the power station.
