My favorite radioactive contamination story is the truck in Juarez that was unknowingly contaminated with Cobalt-60 pellets. The truck died (for unrelated reason) and was scrapped and melted down in an iron foundry. The contamination was only discovered by accident when a truckload of rebar made a wrong turn in Los Alamos National Laboratories and set off a radiation alarm. They managed to track down the truck, find the source of the radiation, and get rid of the contaminated metal. Fortunately, nobody died.