Corporate Information

Press Release (Oct 07,2011)
Usage of the accumulated water in Unit 5 and 6 after the treatment
TEPCO plans to conduct water spraying at Fukushima Daiichi Nuclear Power 
Plant in order to prevent dust scattering and potential fire outbreaks 
from the cut down trees on the site. 

The water accumulated inside the buildings of Units 5 and 6 hardly contain 
any radioactive materials as they consist of the sea water from the tsunami 
and rain water. It is currently stored in the temporary tank and mega-float 
following the removal of radioactive materials via the circulating 
purification facilities.
After the installation of the reverse osmosis system(*1) in September, 
desalination and further removal of radioactive materials have been 

While we have been utilizing the fresh water taken from the reservoir to 
meet the fresh water demand on the site, we will utilize the treated 
accumulated water of Units 5 and 6 for water spraying in order to realize 
the effective usage of water. Such utilization is also effective to 
increase the available space of temporary tanks and the mega-float, which 
are expected to become full in the near future.

The measurement of the radioactivity concentration of treated water 
confirms that the measured level is below the threshold specified in the 
"guideline regarding radioactive materials in the bathing area"(*2).

*1: reverse osmosis system
Facility to desalinate seawater through a reverse osmosis membrane.

*2: Guidelines regarding radioactive materials in the bathing area
Guideline released from the Ministry of the Environment which set the 
threshold of the water quality at 0.03 Bq/cm3 for iodine 131 and 0.05 
Bq/cm3 for Cesium 134 and 137 in total. 
Appendix: Usage of the accumulated water in Unit 5 and 6 after the treatment 
                                                                 (PDF 197KB) 
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