HBO’s Chernobyl-related question. There are radioactive elements in nature. They are unstable and thus constantly radiating particles. But what exactly happens when those particles hit non-radioactive object like human body or whatever else? Isn’t they supposed to interact with it somehow and then fly away instantly? Why and how, instead, objects can harvest those particles, keep them and then re-radiate them over long period of time, and, thus, become radioactive?