TransWorld

Old enough to remember Duck, and Cover drills in school. Or, put your head between your knees, and kiss your sweet a** goodbye.

rickair7777

Way more complicated than that. "Fallout" is not the same as "radiation". Direct radiation would primarily come from the fireball/mushroom... if you're line-of-sight, you're getting cooked, mitigated by range and shielding such as large quantities of dirt, concrete, or water. Drywall and aluminum siding, not so much, but it's better than nothing (and will save you from the third-degree sunburn).

Fallout (contamination) is material, fine particles in this case, which is radioactive in and of itself. Some of that comes from the bomb material itself (a couple hundred kg), but the vast majority would be from dirt at the impact site, which gets massively neutron irradiated and activated by detonation. And then thrown up in the mushroom cloud and distributed via prevailing winds.

The amount of fallout depends on airburst vs. groundburst. A groundburst will make a lot more. The type of soil (or other material) can make a difference, as different elements produce different isotopes with different properties when irradiated.

Typically the fallout has fairly short half-lives, so the direct radiation risk from say having fallout on your skin and being irradiated is minimal after about a month.

The longer-term danger however is from either ingesting or inhaling fallout... once it gets inside you it will deliver radiation directly to your tissue, potentially long-term for years. Potassium iodide tablets (popular and readily available during the cold war) were intended to be taken to prevent ingested radioactive iodine from making itself at home in your tissues.

Here's what you want to avoid, in order (assuming you're far enough away to not get vaporized instantly):
- Flash: Near instantaneous, very serious flashburns. If you're looking at it, you're blind (permanently). Only way to avoid is luck, or duck/cover/shelter if you have advance notice.
- Direct radiation: From detonation, the fireball/mushroom cloud will emit a lot of direct radiation for several minutes at least. While almost anything will protect you from the flash, you need heavier materials to protect against the radiation. Concrete, or lots of dirt or water. Deep end of a pool would work, especially if the side of the pool is towards the blast.
- Blast: you have a few seconds to maybe tens of seconds to hide from the blast behind or under strong structural materials. Avoid windows, they will make shrapnel.
- Fallout: Initially avoid. If roads are clear and you have a working motorized vehicle you can probably outrun it (depending on wind speed). Airplane or adventure bike would be the best ride. Otherwise shelter in place and setup air filtration. If no help has arrived, wait 5-6 weeks (or as long as possible given supplies) before evacuating. Try to get out of the fallout pattern asap, then turn towards your destination. Try to consume only sealed food and water until you get to a known safe area.

Flash: Turn away, instantly duck and cover. When flash subsides seek shelter from radiation and blast if you can get to it within a few seconds, otherwise lay flat and cover your head. After blast, wait about five minutes for direct radiation to drop (longer if upwind), then either evacuate (if you can beat the fallout based on winds and available transport) or shelter in place.