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Press Release (Apr 09,2011)
Results of the investigation regarding tsunami arrived in Fukushima Daiichi Nuclear Power Station and Fukushima Daini Nuclear Power Station
Summary of the results of the investigation regarding tsunami generated by
Tohoku-Chihou-Taiheiyo-Oki Earthquake which arrived in Fukushima Daiichi 
Nuclear Power Station and Fukushima Daini Nuclear Power Station are as 
follows.

At Fukushima Daiichi Nuclear Power Station, on the ocean-side of the main 
building area, inundation with inundation height of approximately 
O.P. + 14 to 15 meters (inundation depth approximately 4 to 5 meters) 
occurred in most of the area. At Fukushima Daini Nuclear Power Station, 
inundation with inundation height of approximately O.P. + 6.5 to 7 meters
occurred in the ocean-side areas, however, only surrounding areas of Unit 
1 and 2 buildings and the south side of Unit 3 building was inundated 
within the main building area.
Accordingly, we have confirmed that the impact of tsunami was relatively 
larger in Fukushima Daiichi Nuclear Power Station than Fukushima Daini 
Nuclear Power Station.

We will try to comprehend further details such as inundation height within
the site and the surrounding areas, together with details regarding inflow
of seawater to buildings and impact on the facilities.
 
The current understanding of inundation height and inundation area of 
Fukushima Daiichi Nuclear Power Station and Fukushima Daini Nuclear Power
Station are as follows.

[Inundation height]
<Fukushima Daiichi Nuclear Power Station>
Approximately O.P. + 14 to 15 meters (inundation depth approximately 4 to
5 meters) across the ocean-side of main building area where reactor 
buildings and turbine buildings are placed. 

<Fukushima Daini Nuclear Power Station>
Approximately O.P. + 6.5 to 7 meters (inundation depth approximately 2.5 
to 3 meters) in most of the ocean-side areas where seawater pumps are 
placed.
Approximately O.P. + 14 to 15 meters (inundation depth approximately 2 to 
3 meters) only on the south side of Unit 1 building within the main 
building area where reactor buildings and turbine buildings are placed.

[Inundation area]
<Fukushima Daiichi Nuclear Power Station>
Across the ocean-side areas where seawater pumps are placed.
Most of the main building area where reactor buildings and turbine 
buildings are placed.

<Fukushima Daini Nuclear Power Station>
Across the ocean-side areas where seawater pumps are placed.
In the main building area where reactor buildings and turbine buildings 
are placed, only surrounding areas of Unit 1 and 2 buildings and south of 
Unit 3 building.
(No un-up over the slope from the ocean-side area to the main building 
area was found.)
 
[Glossary]
-Inundation height
 Height of vestige such as discolored area and remains left on buildings 
 and facilities, measured from the base level. (See drawing below.)

-Inundation depth
 Height of vestige such as discolored area and remains left on buildings 
 and facilities, measured from the ground level. (See drawing below.)

-Inundation area
 Area inundated with tsunami. (See drawing below.)

-O.P. (Base level of Onahama Port construction)
 Base level which is 0.727 meters below T.P. (Tokyo Bay mean sea height). 
Drawing, glossary
Appendix: Result of the investigation on Tsunami at Fukushima Daiichi 
          Nuclear Power Station (PDF 386KB) 
Appendix: Result of the investigation on Tsunami at Fukushima Daini 
          Nuclear Power Station (PDF 459KB) 
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