Fukushima Daiichi NPS Prompt Report 2013

This is follow-up information regarding the water leak from the underground reservoirs at Fukushima Daiichi NPS.

[Progress of preparation for water transfer]
Regarding the water leakage from the connection part (flange) of the transfer pump outlet pipe which occurred during water transfer from the underground reservoir No.3 to No.6, the cause was identified to be an inhomogeneous amount of gap on the flange surfaces. Thus, the flange was recovered by replacing the gasket on the flange.

Since no problem was found as a result of measuring the gaps on other flanges and checking the tightening condition of the flange bolts, the water transfer from the underground reservoir No.3 to No.6 will be started as soon as the preparation is complete.

At the beginning of water transfer, the pump will operate for a short period of time with a small amount of water passing through the transfer line in order to check for leakage from the flanges. Upon confirming no leakage, the continuous operation will be started.

Furthermore, the flanges installed on the transfer line will be protected by vinyl and staff will be allocated for leakage check.

As for the removal of the soil covering the upper part of the reservoir (embankment) where the leaked water is assumed to have been absorbed, further drilling was performed (a total of the drilling depth: 30-60cm) and the radioactivity density on the ground surface has been reduced down to 0.05mSv/h (β＋γ) (max.).

[Measures to prevent the further leakage of the leaked water in the leakage detection holes]
The following is the progress status of the measures to prevent the further leakage of the leaked water in the leakage detection holes as of today.

- Underground reservoir No.1
The temporary pump was put in operation twice to return the leaked water accumulated in the leakage detection hole (northeast/southwest) to the underground reservoir.

- Underground reservoir No.2
The temporary pump was put in operation once to return the leaked water accumulated in the leakage detection hole (northeast/southwest) to the underground reservoir.

- Underground reservoir No.3
The installation of the temporary pump was completed. The work to return the leaked water accumulated in the leakage detection hole (northeast/southwest) to the underground reservoir will be implemented tomorrow or on a later date as necessary depending on the water transfer from the underground reservoir No.3 to No.6.