The site is down, so I can't tell if it models fallout. Not an expert, but I get the impression that you can get lethal fallout a hundred kilometers from the target site. But it would require very bad luck with regards to the wind direction.
There is a very fascinating book detailing the immediate survival of such a scenario.
I have played quite a lot with it - you typically don't get much fallout with an airburst (you do get more dead people), but in the case of nuclear terroism, which would probably be delivered by truck and therefore be a ground-burst, you do.
There is a very fascinating book detailing the immediate survival of such a scenario.