I think the fundamental thing is that it is not a rational fear--nuclear is associated with bombs that flatten cities and radiation is, to many people, a simply

I think the fundamental thing is that it is not a rational fear--nuclear is associated with bombs that flatten cities and radiation is, to many people, a simply scary unknown that they can't touch, smell, or see, but which might kill them. (Many of the people I've met who were against nuclear power didn't really emotionally understand radiation as something you get some of every day anyways--it's a bogeyman that gives you either cancer or superpowers.) Smoke/smog, in comparison, is something you can see and can expect to interact with daily if you're in a city. Despite the fact that it's much more dangerous, people don't perceive it as such.