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Countermeasures for Water Leakage

Contaminated Water Leakage from the Tank in the H4 Area (follow-up info)

September 12, 2013

This is follow-up information about the leakage that occurred at a tank in the H4 area of Fukushima Daiichi NPS.
We are currently planning to install water level observation apparatus in all tanks of the same type as that in which the leakage occurred by November, 2013, and start 24 hour observation from December.

Regarding the cause of the leak, we are assuming that it has come from the bottom part of the tank, since we could not confirm leakage on the side of tank No.5. However, we were unable to identify the leakage location by bubbling tests (a test in which the tank is filled with water and air is sent up from the bottom of the tank).

To investigate the bottom part of the tank directly, tank No.5, from which the contaminated water has leaked, will be taken apart. Prior to this, the adjacent tank No.10 will be taken apart (period: approx. 2 weeks) to make space for the work at No.5. The top lid and the side panels will first be taken off, and then the bottom panels will be decontaminated and checked. The work will be conducted in wet conditions to prevent the dispersal of radioactive materials.

The impact on the surrounding area is also being investigated. Even though we have removed contaminated soil from the surrounding area where the leak had spread, high levels of all beta and tritium are still present from the groundwater near the area. We will continue to investigate the impact.

The past sampling results are posted on the below page.