titorite
Senior Member
For a 1 megaton device you'll have less than a 50% chance of survival up to 200 miles from ground zero.
http://www.nationalterroralert.com/nuclear/
1 Megaton Surface Blast: Fallout
300 Rem
Distance: 160 miles
Causes extensive internal damage, including harm to nerve cells and the cells that line the digestive tract, and results in a loss of white blood cells. Temporary hair loss is another result.
90 Rem
Distance: 250 miles
Causes a temporary decrease in white blood cells, although there are no immediate harmful effects. Two to three years will need to pass before radioactivity levels in this area drop low enough to be considered safe, by U.S. peacetime standards