Fukushima Daiichi NPS Prompt Report 2013

This is follow-up information on influence of rainfall from the approaching typhoon on Fukushima Daiichi NPS.

Due to rainfall from the approaching typhoon, large amounts of rainwater have been accumulated, and water levels have been increasing very quickly, inside the dikes of the C area (east side) and C area (west side) for contaminated water storage tanks. Therefore, it is likely that waters inside the dikes will outflow.

The radioactivity densities (all-β) in accumulated water inside the dikes in these areas are below the density limit by the announcement of reactor regulation for strontium-90 (30Bq/L) as shown below. Further, water accumulated inside the dikes is rainwater. For these reasons, we decided to release rainwater accumulated inside the dikes to the outside of the dikes through dike drain valves as an emergency measure as soon as we are ready.

·C area (east side): 2Bq/L
·C area (west side): 8Bq/L

In cases when a large amount of rainwater has been accumulated inside the dike of any contaminated water storage tank area, we will release rainwater accumulated inside the dike to the outside through a dike drain valve likewise, as an emergency measure to avoid overflow, on conditions that the radioactivity density (all-β) in accumulated water inside the dike is below the density limit by the announcement of reactor regulation for strontium-90 (30Bq/L) and that the thus accumulated water is determined to be rainwater.