Plummeting morale at Fukushima Daiichi as nuclear cleanup takes its toll

[Art_from_Ark]

6. There are various organizations taking radiation readings there

It's not just TEPCO, and it's not just the Japanese government. The Fukushima University of Medicine, for example, has also been monitoring radiation levels, as have the Fukushima prefectural government and various local governments. At any rate, a yearly dose of 20 millisieverts or less per year is considered to be the threshold for repopulating evacuated areas (for reference: Annual radiation in Denver, Colorado is approximately 13 millisieverts per year).

The radiation does not spread out in a nice, even pattern in the area; rather, the higher concentrations tend to follow the course of the prevailing winds, which tend to blow in from the ocean toward the northwest. That is why, for example, Iwaki City 25 miles to the south of the reactors has had radiation levels that have been close to normal for most of the past two years.

But even places like Iitate Village to the northwest have been showing signs of abating radiation levels. For example, the 4 diagrams on page 2 of this report produced by the Kyoto University Atomic Reactor Laboratory show that ambient radiation has been steadily decreasing since March 2011 (higher levels shown in red/orange/yellow, lower levels shown in blue/green. Unit: microsieverts per hour).

http://www.rri.kyoto-u.ac.jp/NSRG/ISP/IitateReport2013-3-17.pdf