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Press Release (May 31,2011)
Plant Status of Fukushima Daiichi Nuclear Power Station (as of 3:00 pm, May 31)
*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 feed water system was initiated.
-From 3:37 pm on March 25, we started injecting freshwater. We are now 
 injecting freshwater by a motor driven pump powered by the off-site 
 transmission line at 6 m3/h.
-As it is suspected that hydrogen gas is accumulated inside Primary 
 Containment Vessel, we commenced the valve opening operation concerning 
 injection of nitrogen gas into the primary containment vessel at 10:30 pm 
 April 6 and commenced injection 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.
-From 11:33 am on May 29, as a part of work to switch the water injection 
 line to the reactor from the fire extinction system to the reactor feed 
 water system, we started water injection through the reactor feed water 
 system in addition to through the fire extinction system. 
 At 11:33 am on May 29, we started the water injection to the reactor 
 through the feed water system piping arrangement at the flow rate of 
 approximately 5 m3/h, and changed the flow rate of the fire extinction 
 system from approximately 7 m3/h to 2 m3/h at 12:01 am, from 
 approximately 2 m3/h to approximately 1 m3/h at 10:38 am and then, from 
 approximately 1 m3/h to 0 m3/h at 6:05 pm on May 30.
 The current rate of water injection is approximately 5 m3/h through the 
 reactor feed water system. 
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 10:19 am on May 31, we changed rate of water injection through the 
 reactor feed water system piping arrangement from approximately 13.5 m3/h 
 to approximately 12.5 m3/h. 
 The current rate of water injection is approximately 12.5 m3/h through the 
 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 happened. 
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 happened. 
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 happened. 
Operation for cooling the spent fuel pools 
-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.
 Since May 27, we have started spraying dust inhibitor to Unit 1's turbine 
 building. We will implement spraying the dust inhibitor to other buildings 
 including Unit 1 to 4's turbine buildings as well as reactor buildings one 
 by one.
-Since 10:08 am on April 19, we had been transferring high level 
 radioactive wastewater from the vertical shaft near the turbine building 
 of Unit 2 to the Centralized Radiation Waste Treatment Facility. At 4:01 
 pm on May 26, a transferring operation was stopped.
-At 2:00 pm on May 1, we started transferring the accumulated water in 
 turbine building of Unit 6 to temporary tanks.
-At 11:00 am on May 10, we started transferring the accumulated water from 
 the underground level of reactor building to the radiation waste treatment 
 facility of Unit 6.
-Since 6:04 pm on May 17, we had been transferring high level radioactive 
 waste water from the underground level of the turbine building of Unit 3 
 to the Centralized Radiation Waste Treatment Facility, but the transfer 
 was suspended due to an inspection on transmission lines and buildings at 
 9:10 am, on May 25.
-At 8:00 am on May 31, 2011, we confirmed oil leakage to the sea around the 
 curtain wall of the water intake canal of Unit 5 and 6, Fukushima Daiichi 
 Nuclear Power Station. We are now valuating the amount of oil leakage and 
 diffused area. While the amount of the oil and the area are still being 
 confirmed, we are preparing oil fence in order to prevent the wide-spread 
 of the oil to the outer sea. We are conducting the investigation on the 
 cause in detail.
-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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