At around 9:30 am on April 2, 2011, 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 flowing out to the ocean. At around 12:20 pm on April 2, we reaffirmed
the event at the scene.
We have implemented sampling of the water in the pit of Unit 2, together
with the seawater in front of the bar screen near the pit of Unit 2. These
samples were sent to Fukushima Daini Nuclear Power Station for analyses.
At around 5:38 am on April 6, we observed stoppage of spilling of water to
the ocean from the crack on the concrete lateral of the pit.
Since April 5, we have been conducting sampling surveys of the water in the
pit of Unit 2 and the seawater in front of the bar screen near the pit.
Regarding the survey results of the detection of three nuclides (iodine
131, cesium 134, cesium 137), we report those as definite results, and for
the other nuclides, we will re-evaluate them.
On April 12, due to the installation of silt fences, we changed the
sampling points from the front of the bar screen of Unit 4 to the north and
the south of the inside of the water intake canal of Units 1 to 4. Since
April 17, we have been conducting an additional sampling survey outside the
silt fence in front of the bar screen of Unit 2, in order to assess the
effect of the installation of the silt fence.
On May 11, 2011, responding to out-flow leakage of contaminated water from
the intake canal of Unit 3, from May 12th, we additionally conducted the
sampling of the seawater inside and outside of the silt fence in front of
the bar screen near the pit of Unit 1, 3 and 4.
On October 16, 2011, we conducted sampling of the seawater near the intake
canal of Units 1 to 4 of Fukushima Daiichi Nuclear Power Station and
analyzed the samples. As a result, some radioactive materials were detected
as described in the appendix.
We reported the above results to NISA as well as to the government of
Fukushima Prefecture today.
We will continuously conduct the same sampling surveys.
*Pit: vertical shaft made of concrete
Appendix1: Nuclide Analysis Results of Radioactive Materials in Seawater
Fukushima Daiichi Nuclear Power Station; the shallow draft quay,
Unit 1-4 screen, and the water intake canal of Units 1-4
Appendix2: Radioactivity Density of Seawater (PDF 42.1KB)