Hello and thank you for coming to our website. We appreciate the opportunity to help you with your questions.
Your biggest worry will be the safety of your food and water supply. At 100 miles, you will be safe from the effects of the explosion and the gamma radiation produced by the nuclear bomb itself. Unless you are directly downwind of the explosion and there is a very strong wind blowing, you should be safe from airborne fallout. (It’s is an interesting fact that gamma radiation strong enough to kill you will activate the rods and cones in your eyes. It’s a joke in the nuclear industry that, if you see a blue flash, lie down because you’re already dead.)
If there is a strong wind blowing from the area of the explosion, then you would want to seal your home as much as possible for at least overnight. The morning dew will bring many of the airborne particles to the ground before they cover 100 miles to get to you.
You will want to avoid any food and water that could come from the affected area. If your water supply is downstream from ground zero, you need to find a separate water supply or invest in a really good water filter.
The long-term danger of a nuclear explosion (as long as you’re outside the area of immediate effects) is contaminated particles. The two types of contaminated particles are beta-radiation emitting and alpha-radiation emitting. Beta radiation emitting particles can cause radiation exposure through the skin and must be kept off of the skin or washed off as soon as possible. Alpha emitting particles can only cause damage if ingested or inhaled. However, if either beta or alpha particles are ingested, they will radiate your body until they work their way through the digestive tract and if they are inhaled, they may stay in your lungs forever, continuing to radiate your lung tissue.
There is a radioactive isotope of iodine that is formed in nuclear explosions. Your body actively takes up iodine and stores it in your thyroid. One of the preventative treatments for radioactive contamination is to take iodine supplements. By flooding your body with clean iodine, your body is less like to store any contaminated iodine that you may get from your food. You will probably want to buy iodine pills to have on hand. Also, for the same reason, if you hunt for food, don’t eat the thyroid of any animals that might have been in a contaminated area.
If you hunt for food, you would be safest to hunt local animals and avoid animals that migrate or may have traveled through a contaminated zone.
If you think there will be nuclear attack, then you would be wise to invest in radiation detectors. There are two types of radiation detectors you will need. One type detects alpha radiation, but it has to be really close to the source of the radiation because alpha radiation is really weak and won’t go through much more than a sheet of paper. The other type detects beta/gamma radiation and can work through a couple of inches of air for beta radiation. If there are any gamma-emitting particles around, you will be able to detect it at a distance and all you can do is get out of the area.
If you go into cities to scavenge, you will definitely need radiation detectors and you will want to wear overalls, boots, and gloves sealed together with tape, at least a surgical face mask, and a hat or hood. Dispose of the clothes as soon as you reach an uncontaminated area and wash thoroughly. Make sure you don’t get your hands anywhere near your mouth or nose until you have thoroughly washed. You can't really manage a clean air supply since air tanks aren't really useful, but there are masks sold with filters to remove particulates.
This should answer most of your questions. Let me know if you would like more information. I can also recommend a couple of books, both fiction and nonfiction about disaster scenarios. I’ll be happy to provide more information if you would like.