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Press Release (May 12,2011)
Plant Status of Fukushima Daiichi Nuclear Power Station (as of 3:00 pm, May 12)
 
*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 nuclear 
  reactor through the feed water system was initiated.
- From 3:37 pm on March 25, 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 7.
- At 10:01 am on May 6th, in order to make nuclear reactor flooded to the 
  top of Fuel range, we have increased the amount of injecting freshwater 
  from approximately 6 m 3/h to approximately 8m 3/h.
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 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 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.
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 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 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 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 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 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 4:07pm to 7:38pm on May 11th, we have conducted water spraying by
  concrete pumping vehicle. (Hydrazine was additionally injected for the 
  period from 4:14pm to 7:36pm)
- We will continuously conduct further water spray depending on the
  conditions of spent fuel pools, if needed.
Others 
- At 1:30 on April 26th, we have started spraying the dust inhibitor
  inside the building.
- At 9:01am on May 10th, we temporarily suspended the transfer of high
  level radioactive wastewater from the vertical shaft near the turbine
  building of Unit 2 to the Centralized Radiation Waste Treatment
  Facility, in order to lay out pipes from the turbine building of Unit 3.
- From 4:18 pm on May 8th to 5:41am on May 10th, we drained the water from
  the condenser of the turbine building in Unit 3 as a preparation for the
  water injection to the reactor through Feeding Water System.
- At 2:00pm on May 1st, we have started transferring the accumulated water
  in turbine building of Unit 6 to temporary tanks.
- At 11:00am on May 10th, we have started transferring the accumulated
  groundwater inside the reactor building to the radiation waste treatment
  facility in Unit 6.
- From May 2, we have started work relating to the set up of exhausters,
  in order to improve the working environment inside the reactor building 
  of Unit 1. At 4:36 pm on May 5th, all of exhausters (6 units) were
  started to operation. At 8:02 pm on May 8th, we stopped its operation,
  removed a duct from double doors and opened a part of the doors. Then we
  fully opened the double doors at 4:17 am on May 9th. We also opened the
  door aside of the carry-in gate for large stuff of the reactor building.
  We measured the air dose rate and confirmed no radiation impact to the
  outside.
- At 12:20 pm, in order to reinforce the power source of Units 3 and 4, we 
  switched the 480V power incoming panel for Unit 4 and a common spent 
  fuel pool from Ohkuma Line No.3 to Tohoku Denryoku 66kV Touden 
  Genshiryoku Line. 
- 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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