"I’m not so sure about the radioactivity not being contagious....And what about that spy who was poisoned with radiation? Wasn’t there a ton of concern about people he had interacted with?"
One must keep two things separate. 1) The source of the radiation and 2) the radiation. Radiation is not "contagious". Someone who is merely been exposed to radiation, as a general rule, will not be radioactive. Someone who is contaminated with radioactive material, i.e. has radioactive atoms on his person, is as radioactive as those radioactive atoms he carries. Obviously (at least I hope it is obvious), the radioactive atoms don't care if they are on a person or not: it will not change the rate which they undergo radioactive decay.
One must keep two things separate. 1) The source of the radiation and 2) the radiation. Radiation is not "contagious". Someone who is merely been exposed to radiation, as a general rule, will not be radioactive. Someone who is contaminated with radioactive material, i.e. has radioactive atoms on his person, is as radioactive as those radioactive atoms he carries.
Obviously (at least I hope it is obvious), the radioactive atoms don't care if they are on a person or not: it will not change the rate which they undergo radioactive decay.