As you know there was a massive Earthquake (and there are still some going on) in Japan followed up by a massive nuclear accident at Fukushima I which has been evaluated 7 on the INES scale grade accident.
Now there are some prediction made by the University of Cologne about how the Cesium will spread around the world.
In the case it does rain
Cesium spreading Wet scenario
and it doesn’t look good.
And in the case it doesn’t rain
Cesium spreading Dry scenario
And it doesn’t look good at all.