See subject. Meaning: I understand that stuff is radioactive, from bananas and us and particles of plutonium and uranium. Which is why if we’re exposed we try to get every last bit of dust of radioactive material (highly radioactive, relative to us), and the micro particles we’ve inhaled, well, we’re fucked and it’s into half-life time.
But if you walk/are exposed to field energy “radiation” that will do its damage, etc, and walk away to a safe region, without any “non-you” radioactive material whatsoever, you are still radioactive, a higher emitter and people should stay away from you, etc.
How does this work? How does atomic/nuclear radiation stick around. Heat–absorbed infrared radiation–I understand, basically. (You can feel the heat coming off a sunburn, or a steak). What am I missing in this analogy?
Sunburn doesn’t work that way. You get sunburn from ultraviolet light. Your skin becomes hot because of the body’s response to the tissue injury, increasing bloodflow through the affected areas to accelerate healing.
I mean, if you’re exposed to light, does the light stick and do you start emitting visible light?
No different for light of higher frequencies (i.e., gamma radiation or x-rays).
Ionizing radiation makes other atoms unstable (e.g. by knocking away one of their ions) causing them to release energy and/or ions (protons, neutrons, electrons) until they reach a stable state*. If enough energy is released by the unstable atoms it will make other atoms unstable, and the process repeats.
*Imagine removing items from one side a balance scale. It’ll be out of balance until you remove an equal number of items from the other side. Atoms are constantly moving and spinning, and require a perfect balance between the forces pushing apart, and pulling together, their component parts.
*note: I’m probably wrong about nearly every detail of that explanation, but fairly accurate with the big picture. *
Ionizing radiation can only affect the electron-nucleus bond. By definition, ionization is an electromagnetic/electrochemical effect. Hence, the nucleus itself is unaffected.
Since radiation of the kinds OP is concerned with is a function of nuclear composition and intra-nuclear processes, ionizing radiation can’t induce those kinds of radioactive emissions.
As has already been pointed out, radioactivity may be induced by means of neutron activation, that is, certain isotopes emit neutrons upon decay, which don’t interact with the electron shell, being neutral and all, but which may be captured by a nucleus, that.in turn may become unstable and decay.
Other than that, though, radioactivity doesn’t stick to you upon exposure—if you get a dose of, say, gamma radiation, then afterwards you won’t be any more radioactive than before. In fact, this is used to preserve food, as it kills germs very efficiently, but is otherwise perfectly safe.
I find myself wondering in this regard about the mechanism that created the large radioactive area around Chernobyl. Presumably it was almost all the result of contamination from the fallout of the exploded material.
In principle, it’s possible to be rendered radioactive through exposure to radiation of any form. In practice, though, it’ll only happen from neutron radiation, and not even always then.
Yes. The Chernobyl disaster resulted in a series of explosions. IIRC the first explosion was a steam explosion. The loss of coolant then caused a prompt critical event, causing the core to basically turn into a crude nuclear bomb. The core’s explosion ejected radioactive material into the surrounding environment. I’m not sure how much radioactive material from the core actually made it out of the plant, but I have read that increased levels of Cesium 137 (a by-product of the nuclear fission reaction) have been found in many parts of Europe resulting from the event. Since the core wasn’t actually designed to be a bomb it didn’t explode very well. Only part of it went critical, blowing the rest of it apart and stopping the reaction. A lot of it just melted, resulting in the famous “elephant’s foot”. There may have been a second steam explosion as well.
What was left of the graphite moderators caught fire, sending radioactive smoke billowing out of the remains of the building. As you’d expect, that contributed quite a bit to the fallout from the disaster.
Chernobyl resulted in a lot of radioactive particulates, which is not what the OP is referring to.