Fortunately (sorta) for most of us I think radiological preps are unnecessary, either you buy it right away or you evac. What we need are preps in case of a limited strike, like someone popping a nuke off in a commercial harbor or something. This would cause temporary shortages and probably a significant amount of civil unrest, especially if you live within a few hundred miles. Here is where stored food and the like will help you ride out the ensuing chaos until the government can restore a sense of stability and supply routes.
Heck, some one pops off a nuke in the panama canal, we will feel it! Stuff will get real expensive for a long while.
But trying to survive in the fallout zone of a nuclear detonation, especially the modern yield warheads, yeah, good luck.