I don't know anything about nuclear power or the physics of radioactive fallout. But if it can be carried long distances by upper level Stratospheric winds then these wind forecast charts showing a 'zonal' or west-east flow of the jetstream across the Pacific don't look so good. Found this German site showing what appears to be a plume forecast. Most of the plumes don't reach North America, though, at least out through a week.
We have to wonder if sites like "Helium.com" advising west coasters to eat lots of brown rice to combat radiation sickness are reasonable or just stoking fear and panic. My guess--and it's just a guess--is that there's no big cause for alarm in North America, at least right now. After all, if the Commander-in-Chief is out playing golf things can't be all that bad.