I looked up some information online about Hiroshima. Now this was merely an atomic bomb, rather weak when compared to a nuclear explosion. Here is what would happen:

Within about a 1 mile radius from ground zero:
a 200 foot deep crater with a 1000 foot diameter. Highly radioactive soil all around. Nothing recognizable remains within about 3,200 feet (0.6 miles) from the center, except, perhaps, the remains of some buildings’ foundations. 100 percent of population is dead.

Between 2 and 1 mile radius from ground zero:
Some of the strongest buildings,— those made of reinforced, poured concrete, are still standing. Ninety-eight percent of the population in this area is dead.

Between 3 and 2 mile radius from ground zero:
Most walls of buildings completely blown out. Bare, structural skeletons of more and more buildings rise above the debris as you approach the 3 mile radius. Fifty percent of the population between the 12 and 5 psi rings are dead. Forty percent are injured.

Between 5 and 3 miles from ground zero:
Any single-family residences that have not been completely destroyed are heavily damaged. The windows of office buildings have been blown away, as have some of their walls. The contents of these buildingsÂ’ upper floors, including the people who were working there, are scattered on the street. A substantial amount of debris clutters the entire area. Five percent of the population is dead. Forty-five percent are injured.

Between 8 to 5 miles from ground zero:
Residences are moderately damaged. Commercial buildings have sustained minimal damage. Twenty-five percent of the population between has been injured, mainly by flying glass and debris. Many others have been injured from thermal radiation — the heat generated by the blast. The remaining seventy-five percent are unhurt.

What About a Nuke?
I live ten miles out so I’d be safe. HOWEVER, in a one megaton nuclear explosion (not an atomic bomb) there is at 100% casualty rate for every person in a 30 MILE RADIUS OF GROUND ZERO. Within 2 to 14 days, everyone in a 90 MILE RADIUS FROM GROUND ZERO WOULD BE DEAD!

That means if a nuclear bomb hit Washington, everyone from Richmond, Virginia to almost Philadelphia, PA would be be dead in two weeks, wiping out nearly the entire population of both Maryland and Delaware!