I teach a little bit of basic nuclear chemistry as it relates to forensic chemistry. My textbook mentioned that the ratio of cesium-134 (at 605 and796 KeV) to cesium-137 (662 KeV) and the ratio of iodine-133 to iodine-131 can be used to determine whether the cause of radioactivity was a nuclear bomb or the meltdown of a nuclear reactor. It also mentioned that there was a handheld device that could be plugged into a cell phone that could be used in this regard but gave almost no specifics. I did a quick search that turned up the paper above. It deals with cesium-137 years after nuclear tests were done.
I am looking for a source of basic information that deals with how one identifies and quantitates various radioactive isotopes, especially these four; it seems plausible that the energy of emission is a characteristic property. If the reading were too advanced for my class, I might be able to summarize it for them.