From article:

Based on a rough estimate, a person standing on soil with 163,000 Bq/kg of cesium-137 would receive about 150 millisieverts per year of radiation, says Chen. This is well above the U.S. Environmental Protection Agency standard of 50 millisieverts per year for an evacuation.

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So, scientists have determined there are CS-137 levels 3x EPA limits within 40 km of Fukushima - why no mandatory evacuation? Is the Japanese government avoiding mandatory evacuations because they don't have any place to put Fukushima refugees , and are incapable of caring for them?

Maybe this piece is relevant:

In the event of a nuclear meltdown, well, go west?

| Al Jazeera Blogs | blogs.aljazeera.net

IWATE PREFECTURE - In the event of the unthinkable (yet horribly possible) nuclear meltdown at the Fukushima Daiichi nuclear power complex, we have to wonder: Where would the evacuees go? How will they be cared for?

After all, the half a million residents left homeless by the March 11 earthquake and tsunami are taxing the government's emergency response... if on top of all of this, there needs to be a mass evacuation around the nuclear plant in Fukushima? What will the roads look like then? Where will these folks go?

[link to blogs.aljazeera.net]