Countermeasures for Water Leakage

August 21, 2013

On August 19, a TEPCO employee on patrol found water leaking from the drain valve of a tank dike in the H4 area of Fukushima Daiichi NPS. The drain valve was closed at the spot.

By measuring the radiation density of the water inside the dike, we confirmed that it came from inside the tank, which contains processed, concentrated water from which Cesium has been removed.

<Leaked water from the H4 area tank (sampling performed at 4:00 PM on August 19)>
Cesium-134: 4.6 x 10¹ Bq/cm³
Cesium-137: 1.0 x 10² Bq/cm³
Iodine-131: Below the detection limit value (3.1 Bq/cm³)
Cobalt-60: 1.2 Bq/cm³
Manganese-54: 1.9 Bq/cm³
Antimony-125: 7.1 x 10¹ Bq/cm³
All β: 8.0 x 10⁴ Bq/cm³
Chloride density: 5,200ppm

The next day, we confirmed that the water level inside the tank near where the water was found had declined by about 3 meters, which we assume that approximately 300 tons had leaked out in total.

We are currently pumping out all the water from inside the tank in question, removing the leaked water from inside the dike and from the soil outside the dike into which it has seeped, and building temporary dams to prevent further spreading of the leak.

We assume that the leak has not reached the ocean, through water sampling of the side ditch, and the monitoring of seawater etc.

We will continue to investigate the cause and promptly take any measures that may be necessary.