This may not be an appropriate place to ask this, and if that is the case please chastise me and cast me out. Given that the members of this forum seem to be very educated and intelligent, especially in regards to these fields I wanted to ask a question. What would be the absolute worst case nuclear reactor meltdown? What sorts of effects could one expect and at what types of distances? And bear in mind, I really am asking about the worst it could possibly get, as in, no one there to SCRAM the control rods, no fire crews responding, that sort of disaster scenario.