Another overflow (2)

Info from TEPCO :

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http://www.tepco.co.jp/en/nu-news/2013/1227436_5484.html

On May 16, sampling was performed in the drain holes of the underground reservoirs No.1-7 (14 locations), the leakage detection holes of the underground reservoirs No.1-4 and 6 (sample could not be collected at 2 out of 10 locations) and the observation holes of the underground reservoirs (22 locations). As a result, no significant change was found with the results compared to the previous analysis results (May 15). Though the all β density in the leakage detection hole (northeast) of the underground reservoir No.1 had slightly increased (to 2.1x10³Bq/cm³) on May 15, the density has decreased to 9.2x10²Bq/cm³ on May 16 which is equivalent to the concentration on May 14 (7.2x10²Bq/cm³).

- At around 8:55 AM on May 17, a TEPCO employee preparing for yard watering found water overflowing from the upper part of Units 5-6 RO treated water tank. The leakage stopped after closing the valve at 9:00 AM on the same day. As a result of site inspection, the leakage area was found to be about 3m x about 20m. The leakage amount is estimated to be 27.5m³ based on the water levels of the D7 tank up to May 16 and the transfer amount of treated water. The water leaked from D7 tank is usually scattered within the power station site and the γdensity and all βdensity of the water were below the detection limits (based on the sampling results obtained on May 16) (Cesium 137 detection limit: 1.5x10^-3Bq/cm³, All β detection limit: 2.3x10^-2Bq/cm³). As a result of sampling performed on May 17 to ensure safety, the γ density and all β density of the water were below the detection limits (Cesium 137 detection limit: 1.5x10^-3Bq/cm³, All β detection limit: 2.4x10^-2Bq/cm³). The leaked treated water has been absorbed into the ground. We consider that the leaked water will not flow into the sea because there are no side ditches near the location of the leakage, and because the source of the leakage is more than 100 m away from the sea. The treated water leakage was caused by overflow from the D7 tank, which is attributed to a failure to perform an operation to switch tanks from the D7 tank to the D8 tank, among eight treated water tanks (D1-D8) in total, while this operation was to be performed on May 16.