Other than a radiologically enhanced explosive device, there really isn't much to fear from a terrorist attack at a nuclear plant. Unless you are looking at the cheap end of Soviet reactor designs, it's pretty hard to break the containment vessel. You have to drop a fairly large plane on it, and that isn't even gaurnteed.
You are worrying too much about something that isn't really as bad as it is hyped. There are other things at your typical chemical works that are much more scary than a "dirty bomb", which is just a frag device with some interesting psychwar aspects. And I'm willing to bet that if you are near a nuclear power plant, you probably have a chemical works nearby, to. And thier security sucks compaired to power plants. If you are prepped for that going boom, you are ready for fall out.
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-IronRaven
When a man dare not speak without malice for fear of giving insult, that is when truth starts to die. Truth is the truest freedom.