I keep hearing about radioactive contamination. If I were to put my shoe in a nuclear reactor, aside from the fact that it would be rather crispy, would it be radioactive? if so, how?
Yes, it would become radioactive. Radiation from the nuclear reactions going on around it would alter the nuclei of atoms in the shoe. Many of the altered nuclei would be unstable, i.e, radioactive.
“The departure of the church-going element had induced a more humanitarian atmosphere.”
Dorothy L. Sayers
Clouds of Witness
Of course, some materials are more susceptable to radioactivation than others. I think its mostly the high-atomic-number metals that you have to worry about, although I could be wrong. I know that copper is very susceptable to radioactivation, and there’s one other one that’s really bad - cobalt maybe? I can’t remember. Anyway, your sneakers are made from mostly low-atomic-number elements - hydrocarbons and polymers - so my guess is they wouldn’t get too “hot”.
I’m sure someone will correct me if I’m wrong.
“For what a man had rather were true, he more readily believes” - Francis Bacon
Mark –
You are right, I think, that it’s the higher-numbered elements you have to worry about, but almost all elements can become radioactive to some degree or another. Carbon-14, for example, is radioactive. It’s just not very dangerous. I believe Oxygen-18 is also radioactive, and so, of course is Hydrogen-2 or -3 (deuterium and tritium).
The lower numbered elements tend to be alpha-emitters and relatively less dangerous, except in special circumstances (like ingestion). But there are oddball nucleotides that are particularly potent for one reason or another, most of which are higher numbered elements, but not all.
When I was a kid there was a scare about radioactive, um, cesium(? I’m not even sure I’m in the right column on the periodic table) created by atmospheric nuclear tests (yes, I’m that old) that would “fall out” of the atmosphere, get eaten by cows and get incorporated into milk in the place of calcium, which we kids would drink and mutate, etc. (Actually I think the concern was it would accumulate in our bones and give us leukemia.)
Predicting what isotopes will be created in a nuclear reaction takes a lot of calculation or a lot of testing (or both), but in general something is going to get hot.
Strontium-90 is probably what they were worried about getting incorporated into bones. It’s chemically very similar to calcium.
Getting back to the original post: Yes, putting something in a reactor can make it radioactive. There’s a specific kind of assay test that involves doing precisely this, and I can’t remember the name of it right now… something like “nuclear activation assay.” Isotopes have specific radiation signatures, and from measuring what kind of radiation is given off and at what energies you can tell what isotopes are present (and from back calculation what was in the original sample).
Kingsnake asks:
Yes, probably.
Now radiactive contamination is not the same as radioactivation. The former is, basically, smearing some already-radioactive stuff on a non-radioactive substrate. The latter is converting stable nuclides into unstable (i.e., radioactive) ones.
If I were to talk into a reactor core (leaving aside the obvious fact that I wouldn’t last thirty seconds in that environment), get some plutonium, and sprinkle it on your sneaker, I would have contaminated it. Contamination can be dangerous, depending on what the contamination consists of; OTOH, most LLW (low-level waste) are things that may have become contaminated (the rule is: “If in doubt, throw it out”).
(As an aside: the fuel elements may be said, stretching definitions a little, to be both contaminated and radiactivated. The difficult, although by no means impossible, element to deal with is that they contain both uranium and plutonium. Both are actinides, and thus are chemically almost indistinguishable (actinides have an electron shell structure similiar to lanthanides (a/k/a rare-earth elements)). Separating them is not a trivial exercise.)
If your sneaker were to be carefully protected from contamination, however, and if I were, dying from the radiation, to leave it in the reactor core, it would probably become radioactivated. As far as fission (and fusion; it wouldn’t be that much cleaner) goes, the gamma (electromagnetic) radiation, and the alpha (effectively, helium nuclei) and beta (electron) radiation, may all be ignored; they all help to kill me, but it’s the neutron flux (slippery little devils that they are) that are the problem. Neutrons are not subject to the electrostatic replusions that bounce alpha and beta particles off of atoms, nor are they so feeble as gamma photons, but will penetrate to and be absorbed by the nuclei. This will start by producing a nucleus that is (by definition) one neutron heavier than before; most (but not all) nuclides can handle this. However, those neutron-heavy nuclei will absorb another neutron, and so on, until they do become become unstable. Those unstable nuclei will eject beta particles; whether they will be positive betas (positrons) or negative betas (electrons), how energetic they will be, and how energetic any accompanying photons will be, can theoretically be calculated from first principles, although the math is beyond me. However, tables of these things can be found, even on the Web.
“Kings die, and leave their crowns to their sons. Shmuel HaKatan took all the treasures in the world, and went away.”
Anecdote and food for thought on the topic:
At the end of my second year physics course we did a radioactivity lab. We had Gieger counters, which were more for play, and a more serious radioactivity counter for our experiment. Our experiment revolved around disks of indium that had been exposed to a slow neutron source, making them radioactive.
However, something on the sidelines was more memorable. One of the students mentioned that they had knee surgery a few weeks prior, and had been given some x-rays at the time. I was amazed at the fact that a Gieger counter would go from a click once every few seconds to about ten clicks a second when place over his knee!
By the way, deuterium isn’t radioactive; it will fuse nicely under the proper conditions, but just sitting on a shelf it’s stable.
I think we have a small amount of natural radiation that Gieger counters pick up. I remember using one once…why the counters themselves never become radioactive? Shrug.
When passing the Geiger counter over any part of his body other than his knee, it counted no more radiation than it did in the open air. The noted jump only occured within a few inches of his knee.
Of course this was still a tiny level of radioactivity. Putting the Geiger counter close to the indium samples would make the clicks far too fast to count, and yet the indium radioactivity was still low enough to be safe for us to handle without protection.
torq –
Yes, it was Strontium-90 and you’re right about deuterium.
/b]Akatsukami** –
That’s a good point about the distinction between contamination and activation.
Now for the big question – does my approval matter? 
pluto writes:
Thanks, pluto. I probably do not do enough to acknowledge either the contributions of others, or the compliments that are thrown my way.
Alas, no. In fact, my approval doesn’t matter (I was sure that God had appointed me His junior partner, but I seem to misplaced the rescript ).
“Kings die, and leave their crowns to their sons. Shmuel HaKatan took all the treasures in the world, and went away.”
he said glowingly.