It's too early to say. Every hour the story changes. One minute the radiation levels are phenominally high. The next minute they are very low. It's unfortunate that the news is so spasmodic and inconsistent for the year 2011.
If there is a full meltdown at one of the reactors and the wind blows West or North then other parts of the World, as well as Japan, will be affected. Psychologically, all the World is now affected. So much so that there will be no new nuclear power stations built within the next decade and the older stations will be closed down. From an engineering point of view, it's not really necessary but from a political standpoint, that is the only way to avoid gross civil disruption in America, Europe and Asia.