Seabed Radioactivity around Fukushima

Sharing our early measurements of Cesium-134 in riverbeds and seabed
near Fukushima Nuclear Power Plant

In October 2014, a small team of volunteers sailed near the Fukushima power plant to sample seafloor sediments. The samples have been analysed, the numbers and maps are below.

Image on Flickr :

Sediment Samples Measures Dataset :
Fusion Table :

Sediment Samples taken on the seafloor : 2014/10
Reference date for radioactive decay : 2011/03/11
License : CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Samples collected by Cesar Harada |
Samples analyzed by Dr Olivier Evrard |
Map by Cesar Harada & Anant Majumdar |
Reviewed by Kalin Kozhuharov |

Device used to measure our sediment samples during 24 hours each, in France CNRS, LSCE.

I am not in the position to say if this is “safe” or “unsafe” to swim in these waters, or tell you should OR should not eat the fish from around Fukushima. The maximum “acceptable” level for Cesium in fish is 100Bq/Kg set by the Japanese Food Safety commission. We measured environmental radioactivity / seabed measurements, not fish.

We are now waiting for more measurements from the rivers, and will compare our findings with deep sea measurements in the hope of producing a more comprehensive map of riverbeds and seabed radioactivity in Fukushima Nuclear Power Plant vicinity and further out. It’s been documented that hotspots can be found often times in depressions, and potentially as far as the other side of the Japanese main island near Niigata.