By the way ... let me throw out a useful fact.

If you go back and look at the atomic testing that was done in the USA in the 1950's (Nevada test range), you will discover that the radiation that was released across America did not fall evenly. Many people assume that the radiation blows in the air as a dust cloud. Although dust problems are possible. there is another concern. In fact, local "hot spots" of radiation in the USA were often associated with areas of rainfall. The radioactive dust from the nuclear blast gets picked up into the clouds, then comes down later in the subsequent rain.

If you are generally "downind" from a nuclear detonation, you need to ba careful about contaminated rain water in the days after the event.

Close to the bomb blast, your main concern is heat.

other Pete