It is pretty surprising to hear in perfect german to the energy secretary of the european union telling that the situation in Japan is "apocalyptic". When people who knows what are talking about (not like journalist) say such severe words it means you have to take them into account. Let us examine the situation in the Fukushima nuclear station.
The nuclear reactors 1, 2, 3, and 4 are not refrigerated anymore. That is a fact. And it becomes, then, possible that one or more of the reactors melt and react with the air or the steam and blow up breaking the reactor vessel expelling a huge amount of radioactive dust and gas to the atmosphere. This is what happened in Chernobil. We all remember those satellite images of the radioactive mass of air moving through the european sky towards the north pole.
If this situation, the explosion of one or more of the nuclear reactors rel, appears in the Japan islands two scenarios are possible:
1. The air pushes the radioactive particles tail to the ocean. But, this situation is not probably to hold untill the end of the situation.
2. So it will arrive a moment where the radioactive cloud will sit on the Japan territory contamination to the 250 million overcrowded population.
If they notice that living there makes health worsen i would not disregard a massive migration of people running away from the islands. The only place they can go is to China. And some regions of Japan will become completely empty for years.

This is an image of the explosion of the building of the third reactor which explotes. This explosions seem to be done with the purpose of protecting the reactor vessel.