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Press Release (Apr 23,2011)
Plant Status of Fukushima Daiichi Nuclear Power Station (as of 4:00 pm, April 23)
*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 0:30 pm, April 23rd, we started water spay to Unit 4 by the 
 concrete pumping vehicle. 
-We will conduct further water spray depending on the conditions of spent 
 fuel pools, if needed.
Others
-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. 
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