If you are exposed to particulate dust or debris, once you are inside an area that is enclosed, be mindful of everywhere you go and everything you touch, and consider them contaminated. The way radioactive contamination like dust particles are removed from people in places like nuclear power plants is with shaving cream. The way shaving cream expands on the skin lifts hair by design, but also lifts particulates so that they may be rinsed off.
The most dangerous radioactive elements have the shortest half lives. The quantity of particles is still important. Like the elephants foot at Chernobyl is still deadly to a human standing in the same room for only a few minutes due to quantity. However, just after a nuclear mass murder event by a subhuman psychopath, staying away from the earliest byproducts of the nuclear reaction is critical. These are extremely harmful even in the fine dust on the outskirts.
Nuclear technology is our most irresponsible atrocity we lack the time perspective to clearly understand. Imagine if the wars of the crusaders 1000 years ago were causing people to die directly as a result of their weapons, not because of geopolitical fallout. Nuclear is an atrocity for any use because of our incompetent governments, but it is a far greater crime on all future generations for thousands of years to come. History will make us the most despised humans in the entire lineage of the species. This is the only legacy any of us will be remembered for.