https://en.wikipedia.org/wiki/Goi%C3%A2nia_accident
Stuff of nightmares.
Stuff of nightmares.
If people are strongly affected by the radiation, then it's probably not going to be that long until the problem is tracked down and dealt with.
I suppose the worst case scenario would be if the radiation was in a place where it wasn't affecting people as acutely and lots of people were passing nearby it, such that the existence of the radiation wouldn't be as obvious or as easy to track down.