Fukushima soil contamination

12 04 2011

I spent the last two nights arguing with a friend about the potential danger of radioactive fallout from Fukushima.  I contended any US fallout was negligible, he disagreed.  This led to reading a Science magazine post outlining the high soil contamination readings near Fukushima, and then to the real raw data, and comparisons to Chernobyl contamination.  We ran the numbers, and still disagree re: the US, but for Japan, they look bad.  If Chernobyl is a valid guide, which is a pretty conservative estimate of the caution of Japan’s government, there will be permanent closure of some towns that are >30km from the plant.

Here is a crude map I whipped up comparing the soil cesium-137 levels that led to restricted access to areas around Chernobyl, with that reported by the Japanese Ministry of Education, Sports, Science and Technology. Here is a directory with the compiled source data, updated daily.  The results are very disturbing.  Anything above 1500 kBq/m^2 was permanently closed near Chernobyl. Anything above 555  kBq/m^2 was permanently restricted.  If my topsoil conversion factors are correct, and they do match the expert’s assumptions in the Science mag story, then there are numerous villages above 555 kBq/m^2 level that are fairly far from the plant.  The 100 kBq/m^2 levels at a distance of 80km are also worryingly high. These aren’t cherry-picked readings to make things look dramatic, they are the rough average of many repeated samples across weeks.  No wonder the government finally upgraded the incident to a level 7. Click the picture for the big view.

Comparison to the whole of Europe is also illuminating, the numbers are the same scale as above.