At around 9:30 am on April 2nd, we detected water containing radiation
dose over 1,000 mSv/h in the pit* where power supply cables are stored
near the intake channel of Unit 2. Furthermore, there was a crack of about
20 cm length on the concrete lateral of the pit, from where the water in
the pit was out flowing. At around 12:20 pm on April 2nd, we reaffirmed
the event at the scene.
We have implemented sampling of the water in the pit, together with the
seawater in front of the bar screen near the pit. These samples were sent
to Fukushima Daini Nuclear Power Station for analysis.
At around 5:38 am on April 6th, we have observed stoppage of spilling of
water from the crack on the concrete lateral of the pit. For the sake of
completeness, we put further reinforcement for the stoppage of leakage and
consider countermeasure including continuous injection of coagulant. We
will also note the water level of turbine building of unit 2 remain
unchanged. We will further investigate if there is any other leakage.
Since April 5th we have been conducting sampling of seawater in the pit
and in front of the bar screen near the pit. Regarding the results on
three nuclides (iodine 131, cesium 134, cesium 137), we report those as
definite result. As for other nuclides, we will revaluate in accordance
with the preventive measures formulated after being given warning from
Nuclear and Industrial Safety Agency (NISA) on April 1st.
From April 12th, with the installation of the silt fence, we changed the
sampling points from the front of the bar screen, Unit 4 to inside of the
water intake for Units 1 to 4, north side and south side.
On April 15th, 2011, we collected samples from seawater in the pit and in
front of the bar screen near the pit. As a result of the nuclide analysis,
radioactive materials were detected as described in the attachment.
Accordingly, we have reported the result of the analysis to NISA and
* pit: a vertical shaft made of concrete
Appendix: Result of Nuclide Analysis of the seawater at the shallow draft
quay, Unit 2 screen and the water intake canal of Unit 1-4
Appendix: Radioactivity density of seawater(PDF 17.6KB)