If you are NRT bound
 

I've created Google Earth Layer showing the locations of the nuclear power plants in question. Fukushima has major problems and the other 2 are less serious.

There are radius circles at 50, 100 and 200kms around each plant and weather/surface wind links that will be useful if you are down in NRT, about 200kms away. There is also an interesting Google Earth layer put out by the USGS on the incidents page link.

Japan Nuclear Incident Layer - Google Earth required

Good luck to all if you are in the area.