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Press Release (Apr 17,2011)
Plant Status of Fukushima Daiichi Nuclear Power Station (as of 6:00 pm, April 17)
  
*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. 
- From 7:35 pm on April 12th, we started transferring the high level 
  radioactive accumulated water in the trench of the turbine building to 
  the condenser by an underwater pump. At 5:04pm on April 13th, the 
  scheduled transfer was completed. 
 
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 around 5:24 pm on March 23rd, when we switched the temporary Residual 
  Heat Removal System Seawater Pump, it has stopped automatically. At 
  around 4:14 pm on March 24th we replaced the pump, and restarted cooling 
  of reactor at around 4:35 pm. 
- 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. 
- In relation to the two seawater side pumps of the Residual Heat Removal 
  System, we switched the power source from temporary to permanent at 3:38 
  pm and 3:42 pm, Mar 25 respectively. 
- At this moment, we do not consider any reactor coolant leakage inside 
  the reactor happened. 
 
Operation for cooling the spent fuel pools 
- From 5:39pm on April 17th, we began to spray water to Unit 4 by a 
  concrete pump 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 evacuation to inside 
  for those residents from 20km to 30km radius of the periphery, because 
  it is possible that radioactive materials are discharged. 
- From 7:03 pm on April 4th to 5:40 pm, April 10th, we discharged to the 
  sea approximately 9,070 tons of the accumulated low level radioactive 
  water stored in the Centralized Radiation Waste Disposal Facility. Also 
  from 9:00 pm on April 4th to 6:52 pm, April 9th, we discharged to the 
  ocean approximately 1,323 tons of the low level radioactive subsurface 
  water stored in the sub drain pits of Unit 5 and 6. 
  Regarding radioactive concentrations at measuring points including those 
  adjacent to the power station due to the discharge of the low level 
  radioactive stored water to the ocean, no significant change has been 
  found, though we compared them with the transition of concentrations for 
  a week before the discharge. 
  The total amount of emitted radioactivity is approximately 1.5 x 1011 
  Becquerel. We evaluate approximately 0.6 mSv of effective radioactive 
  doses per year per an adult as the impact on the discharge of the low 
  radioactive stored water to the ocean if an adult eats adjacent fish 
  and seaweeds every day. The amount (0.6 mSv of effective radioactive 
  doses per year) is one-forth of annual radioactive dose (2.4 mSv) to 
  which the general public is exposed from nature and equivalent to that 
  when we evaluated before discharging the water to the ocean. 
- From 2:30 pm to 3:45 pm on April 15th, we installed 3 sandbags 
  containing zeolite (as an absorbent material) between the screen pump 
  rooms of the Unit 3 and Unit 4. 
  Also, from 9:00am to 11:15am, we threw in two sandbags between the 
  screen pump rooms of Unit 1 and 2, and five sandbags between the screen 
  pump rooms of Unit 2 and 3. 
- From 10:19 am to 5:00 pm on April 15th, we transferred distribution 
  panels of the pumps to inject water to the reactors of Units 1 to 3 as 
  a countermeasure against tsunami. 
- At 2:34pm on April 17th, power supplies to a common spent fuel pool was 
  temporarily stopped because a breaker at the upstream side was released 
  due to an electrical short circuit which was caused by an insufficient 
  treatment of the end of the unused cable which was connected to the 
  power source of the common spent fuel in parallel. However, after 
  removal of the cable and checkups, at 5:30pm, the power supplies to the 
  common spent fuel pool was restored. 
- 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. 
- 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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