Is there any material in existence that can serve as radiation shielding and will not itself become radioactive if exposed to intense radiation indefinitely, or does everything eventually become radioactive itself, too, if exposed to radiation for long enough?
Does the lead lining in radiation shielding have to be replaced if it’s exposed to intense radiation for long enough and becomes radioactive itself?
It depends on the type of radiation. It requires neutrons to make stuff radioactive. If you have sources that don’t emit neutrons the only thing to worry about would be contamination due to source leakage. If you do have neutrons you have activation. Some materials are easier to activate than others, and those usually also decay quickly. Even if the shielding doesn’t easily activate you can have impurities or structural material holding the shielding that can contaminate the shielding.
No. After the exposure is taken, everything is fine to touch, be near, etc. Xrays are light waves with a shorter wave length that visible light. Once the “light is of” so to speak, there is no danger to anyone. They don’t cause radioactivity.
ETA: assuming you are talking about shielding used for radiographs.
Strictly speaking, in principle you could transmute with any sort of radiation at all. But for anything but neutrons, it’d have to be at ludicrously extreme energy, that you simply can’t get from most potential sources.
Technically, alpha radiation can transmute one nuclide into another radioactive nuclide without ludicrously extreme energies. For example, you could have
alpha particle + fluorine-19 -> sodium-22 + n
and the sodium-22 then decays to neon-22 via emission of a gamma, a beta, and another gamma. The half-life for the beta-emission is about 2.6 years, so if you bombarded some fluorine with intense enough radiation for long enough, it would stay radioactive for some time after you stopped the bombardment.
However, this is highly dependent on what isotope you’re bombarding with radiation, and I suspect that most isotopes don’t do this. Also, I don’t believe this can happen for beta radiation or gamma radiation (or X-rays, for that matter, which are just lower-energy gamma rays.)
I’d assume that any isotope that is the product of radioactive beta decay could be transmuted back into its source when exposed to beta radiation and thereby become radioactive again. You might have to hit it with antineutrinos at the same time I suppose though it might be able to give off a neutrino instead.
There’s something about a limit of about a mega Electron Volt worth of energy in the before and after…
even then you basically you must hit the nucleus’ neutron with an with anti-neutrino and then it can emit the positron.
Isilder, I don’t understand your reply. I thought that essentially all particle reactions were reversible. I understand there are some CPT problems, but these don’t apply here. And there aren’t any macro-entropy problems.
There’s probably a fine-tuning problem with the energies (which, ultimately, makes it an entropy problem). If, for instance, a particular isotope decays by emitting a beta particle and a neutrino at a total energy of 1.739 MeV, then the reverse reaction would start by hitting the nucleus with a beta particle and a neutrino at that energy. Too low an energy obviously won’t work… but too high of an energy might not, either.