When something non-radioactive has been exposed to radiation, and itself becomes radioactive, what happens to it?



Does it mean that some of the atoms have absorbed neutrons and are now an unstable isotope thus emitting their own neutrons? How are irradiated things dangerous?

In: Physics

This doesn’t normally happen. Radiation *almost* never makes something radioactive.

There are two situations in which it does. The first, you already seem to have a decent idea of. Things exposed to *specifically* neutron radiation can become radioactive through nuclear transmutation (a physical change in the composition of the nucleus, in this case adding a neutron). However, most of the time, they will emit a different kind of radiation, and so the process cannot be repeated.

The other situation is the more common one – absorption or adhesion. If you hang out around some radioactive stuff, odds are good that some of it will stick to your clothes or be absorbed by you through breathing. The radiation itself doesn’t make you radioactive, but the radioactive shit that sticks to you and gets inside of you does. This is why marie curie’s body is so radioactive.

They can get radioactivated, like you describe – either an alpha capture or a neutron capture can turn a stable nucleus into a radioactive nucleus.

Or, if the two materials actually touch, breakdown products can transfer from one to the other and so could the original material, if it’s soft enough or if it’s dissolved/powdered.

I was reading about this years ago after watching the Adrian Edmondson movie, where he describes the graphite moderator as “just…unbelievably radioactive”. The neutron flux in the reactor does convert some of the graphite into carbon-13 and carbon-14, but I think the bigger problem was fission products like strontium and barium sticking to, or soaking into, the graphite…? Carbon-14 just doesn’t seem that scary to me because of its long half-life.

[Edit: Iodine, too.]

If you irradiate a heavy element you can convert it to a more radioactive form, like converting uranium into plutonium.

That is a rare edge case though, it’s mostly just a myth from cartoons and comic books that radiation itself makes things radioactive. The real thing is that when people talk about cases they’d be around radiation it’s hypothetical talk about a nuclear war or powerplant explosion or something where the physical dust and material would be physically on things. if something was placed on an object that was radioactive from bomb fallout it would itself become radioactive because transferring even a tiny bit of ash or dust would be enough to be a source of radiation.

Fusion reactions like those aren’t common in practice, but that’s the general idea, yes. An irradiated object that itself becomes an emitter in this way is dangerous for the same reason any emitter is dangerous; ionizing radiation can mess up all sorts of things in otherwise tightly managed biological systems, if it can penetrate far enough or the emitter gets inside you. Specifically, knocking out atoms or adding a neutron here and there disrupts/alters the function of proteins and introduces errors in the DNA that may prove unfixable.

There is a difference between radioactive material and radioactivity. Radioactive material contains elements that are unstable and decay into stable forms by releasing energy and particles. That release of particles and energy y (called radioactivity) has various forms.

Radioactivity making some other non-radioactive element radioactive is very rare. This is becuase specific or sufficient energies are needed to transform elements into radioactive ones.

Bananas contain a naturally ocurring radioactive element. If you remove the radioactive element from bananas, Potassium-40, and put it into an apple, the apple would now be considered radioactive material because it contains potassium- 40. Nothing else in the apple would be radioactive, even when exposed to the radioactivy from the potassium-40. If you put enough potassium-40 into the apple, damage would start to occur to the molecules of the apple caused by the radioactivity of the potassium 40, but the non radioactive elements in the apple would not become radioactive.

In the circumstance when the energy of radioactivity is specific or sufficient enough to alter specific elements in a material, then a non radioactive material can become radioactive. Note that this is a reaction and it is not the result ofthe radioactivity “contaminating” the material. Radioactivity cannot contaminate anything. However something can be contaminated by radioactive material.

The creation of radioactive material by radiation always involves a reaction. For example, if you bombard a slab of bismuth metal with alpha radiation (a type of radioactivity, not radioactive material) some Bismuth atoms will absorb the ralpha particles, release 2 neutrons, and turn into astatine-211. Astatine-211 is radioactive.

The bismuth slab, which is still mostly bismuth, is radioactive material only because it contains atoms of astatine-211 which is radioactive because it releases radioactivity.