From my understanding, nuclear fallout happens when dust or debris becomes irradiated. But does this include the air molecules even with the absence of dust?
And lastly, if you had some, say sand that was contaminated by fallout, how does the radiation emitted work? Would it be similar to heat? In the sense the closer you are to the sand you would feel more heat? I get really confused with why it’s just dust and debris, and how far they can emit radiation.
Thank you kindly in advance 🙂
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There are three main components of nuclear fallout:
* Fission products — these are the remains of the atoms that got “split” by nuclear fission. They make up the most highly-radioactive part of nuclear fallout.
* Induced radioactivity — these were atoms that weren’t radioactive before, but after getting a big blast of neutrons, transform into more radioactive versions of their original selves. These tend to be pretty short lived, but are still an issue.
* Un-fissioned bomb fuel — all nuclear weapons only split some of their bomb fuel, and so there are bits of plutonium, uranium, and heavier atoms (some created by neutron bombardment, like einsteinium). These tend to be very long-lived, so they are not as immediately radioactive, but they are part of the long-term contamination risk.
The fission products and unfissioned fuel are part of the fireball, and become part of the cloud. Here is where you dust and debris come in: if the dust and debris mixes into the fireball (e.g., from a surface or near-surface burst), then those fission products will attach to them. This makes them heavier and causes them to “fall out” of the cloud earlier. It’s not the dust that’s the problem, it’s the fission products attached to the dust.
The induced byproducts are just anything within the area of the neutrons created by the explosion. So this includes the ground, includes metals, includes whatever. It can also include the air: nitrogen, for example, becomes radioactive carbon-14 under these conditions. So to answer your question, yes, air can be part of this.
The up-shot here is that when something light like air becomes radioactive, it doesn’t tend to have a _huge_ impact, because it is circulating for a long time before it gets brought back down to Earth and enters into ecological systems (e.g., by rain), making it relatively diffuse wherever you go (and not concentrated — it’s diluted). So radioactive carbon in the air is a long-term chronic risk (it increases everyone’s radioactivity by a tiny bit), not an immediate “if you walk through here after the detonation, you will get radiation sickness and die” risk (which is what the fission products are, if they fall out of the sand). The Soviet weapons designer Andrei Sakharov estimated that every megaton of nuclear explosion in the atmosphere would create enough carbon-14 to contribute to the deaths of 10,000 people over the course of 8,000 years (so a little less than one person per year).
As for the last question, if something is very radioactive, it can be felt as heat. The solid spheres of plutonium used in the first atomic bombs, for example, were radioactive enough that they were hot to the touch.
But most radioactivity is like a type of light that you can’t see without special instruments. So you wouldn’t feel anything warm to the touch, even though it could burn you (beta burns are a type of radiation burn).
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