eli5 How can non-radioactive elements and materials become radioactive?


I understand how uranium is radioactive because it essentially tears itself apart but what I don’t understand is how like plastic and metal tools used to handle it becomes radioactive.

In: 1

Long story short, the plastic and metal material itself is not becoming radioactive.

What does happen is parts of the *actual* radioactive material can rub off, brush off, scrape off, etc. and cling to the plastic or metal. This is generally called *contamination*. So now you’ve got a metal tool that also has some radioactive material on it spewing out radiation. In some cases it is possible to clean that tool or material off (decontaminate).

The radioactivity detected from tools used to handle radioactive materials is just from trace amounts of the material being transferred to it so it’s still uranium atoms that are decaying, they’ve just been transferred to the tool in question

If you bombard a material with the products of radioactive decay, like neutrons, some of those neutrons might collide with the atoms in the material making them transform into a unstable version of of element which may then undergo radioactive decay. Or little bits of radioactive dust might settle into the material and cause it to become contaminated with radioactivity that way.

Metals generate dust. That dust gets everywhere. Especially when you’re machining it. That dust is radioactive, in the case of uranium. It can also physically absorb into the surface if there’s a lot of heat and close contact, such as machining.

Radiation *can* make other things radioactive, but not usually the radiation from uranium.

For the most part it is just contamination with radioactive particles. The tool used to remove the fuel rods will pick up some surface contamination. If its Uranium that’s not too bad because it decays slow, if its contaminated with some of the fission products it’ll be a lot more radioactive for a bit

That said, metals in the reactor itself can become radioactive. Both fission and fusion produce high speed neutrons which can strike an atom and join with it, this is called [Neutron activation](https://en.wikipedia.org/wiki/Neutron_activation). Basically all iron that you can find is stable, but if you start smacking it with neutrons then some of that 5% that is Fe-54 becomes Fe-55 which is radioactive with a 2 year half life so you will have taken non-radioactive steel and made radioactive steel

For it to matter you need to be hitting it with a lot of neutrons to create a lot of Fe-55 so a steel liner of a reactor may have issues after decades but an iron hammer that gets near a fission reactor won’t have any notable changes