Corporate Information

Press Release (Apr 13,2011)
Detection of trace amount of radioactive materials by the regular monitoring at Kashiwazaki-Kariwa Nuclear Power Station (continued report)
We have been measuring radioactive materials by the dust radiation monitor*1 
at three of the monitoring posts installed at the station boundary, 
collecting the dust in the atmosphere as environmental sample with a 
filter. On April 13th, we detected trace amounts of Cesium that slightly 
exceeded the detectable lower limit from filters installed at three 
locations when we conducted the regular monitoring for March 2011. 
Detected nuclides are Cesium-134 and Cesium-137. (please refer to the 
attachment for more information).

Therefore, TEPCO checked operating conditions and works of all units, 
readouts of the exhaust stack monitors and the sampling result of water in 
the reactor. As no abnormality was detected, it is presumed that 
Cesium-134 and Cesium-137 released into the atmosphere from Fukushima 
Daiichi Nuclear Power Station were collected and detected in 
Kashiwazaki-Kariwa Nuclear Power Station.

The monitored figures of Cesium-134 were the two millionth part of the 
density limit in the air, 2 x 10-5 Bq/cm3 (Announcement density*2), 
meanwhile, Cesium-137 were the four  millionth part of 3 x 10-5 Bq/cm3. 
(Announcement density), these figures indicated extremely low level.
In addition, the aggregate monitored figure of radiation dose from Cesium 
was approximately 7 x 10-7mSv per year. That was the three millionth part 
of radiation a person receives from nature annually (2.4 mSv). Furthermore, 
it is far lower than radiation dose from one time chest X-ray examination 
(0.05 mSv).

As part of the regular sampling analysis*3, we will continue monitoring 
the radiation of environmental samples such as seawater close to the plant, 
soil, pine needle and etc.

Readouts of Monitoring Posts located at boundary of the station and dust 
radiation monitors attached to Monitoring Posts are within the normal 
range. There is no impact to the surrounding environment.

Attachment-1: Monitoring result of radioactive materials by regular 
              monitoring in Kashiwazaki-Kariwa Nuclear Power Station
Attachment-2: Detected location of trace amounts of radioactive materials 
              by regular monitoring

*1: Dust radiation monitor
    Measurement equipment to monitor the radiation of the dust in the 
    atmosphere is collected consecutive every 6 hours with a filter. 
    We have been implementing detailed analysis of used filter periodically.
    Three dust radiation monitors are installed out of nine points of the 
    monitoring posts near the station boundary.

*2: Announcement density
    This density is established as the equivalent radioactive dose of 1 mSv 
    per year if a person continues breathing the same through the year.

*3: Environmental sampling analysis
    We are monitoring the radiation of seawater close to the plant, soil, 
    pine needle, milk and etc periodically.

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