This is really terrible. I'm currently taking a course on alternative energy systems and though nuclear power is (obviously) dangerous, it is also the cheapest. Nuclear power is something the world should be seriously considering due to how quickly we are burning through our fossil fuels. Huge disasters such as this are really big set backs as far as the public opinion on nuclear power is concerned -- holding us back even more from research to make it safer.
As flan said, as horrible as this is hopefully it will not be worst case scenario. My heart goes out to everyone in japan.