What were the effects of the heavy atmospheric nuclear testing done in the 40s, 50s and 60s on life on earth? The Tsar Bomba alone had to create some seriously irreversible fallout damage for most of the planet, right?
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Not really a lot. Almost all damage is reversed pretty easily by nature. There is a market for pre-nuclear steel, as almost all steel produced since the nuclear era has above baseline concentration of radioactive isotopes. If you’re building shielding for an exotic scientific instrument measuring radiation, you’ll pay extra for old steel without these traces.
As far as the rest of the world, it’s all in the past. Some permanent damage was done to some Pacific atolls, but that was physical damage – not fallout damage.
Tsar bomba actually didn’t produce all that much fallout compared to smaller nukes. For one it was an airburst, which limits the amount of fallout created and dispersed, and on top of that most of its explosive energy came from a fusion reaction which again doesn’t produce much fallout. Tsar bomba was a surprisingly clean bomb.
Tsar Bomba resulted in a very small amount of fallout compared to their yield, it is in fact the nuclear explosion with the loser fallout to yield ration.
Fallout is radioactive material that falls to the ground. It is fission produced and atoms that have been hit by neutron radiation and become radioactive elements. It is material with half lives in days or years that will have a major impact. If halflife is in second it will be gone before anyone is exposed and if is is hindered of years the intensity will be very low
Let’s first look a the neutron capture part. Tsar Bomba exploded in the air so neutrons were captured bu the atmosphere. The oxygen become radioactive nitrogen with a half-life of 7 seconds so it is quickly gone. The nitrogen primary becomes Cabon-14 with a half-life of 5700 years. The carbon will if I am not mistaken react with oxygen and you it becomes carbon dioxide so not something that falls to the ground. So air bursts do not produce elements that are especially dangerous.
If you do a gound blast then neutrons hit lots of other elements and can produce have half-life in the dangerous range. The atoms will be part of solid material so they say on the ground or fall down as dust.
The last look at the fission products. Tsar Bomba is a 3 stage design with an initial fission stage that is used to detonate a second fusion stage and it will initiate another fusion stage. 97% of the energy came from the fusion stages. The total yield is 50Mton and 1.5Mton was generated by this initial stage
Fusion produces primary light stable elements or elements with a short half-life, So the amount of fall out from they are low. The initial stage used uranium and did produce a lot of radioacvie material with half that are bad for us, but it is an air blast and the result is they spread out over a very large area.
Once again if it was a blast at ground level or with the fire ball in contact with the ground radioactive it gets worse. The radioactive element from the fission will sick to dust and other material and fall down to the ground a lot faster so you get dangerous radiation levels. You get lots of fallout if you throw up a mixture of direct and radioactive material in the air. There is a reason that even when atmospheric testing was done most were not ground detonations.
Thermonuclear weapons, that is when you have fission and fusion sages, usually have use lost of U-238 in casing pushers etc. It can’t sustain a chain reaction but is can go through fission if hit with a neutron, The fission and fusion stag do produce a lot of neutrons so by using U-238 you get extra yield and not extra weight and minimal extra cost. The yield of the initial
Tsar Bomba initially was designed that way too with a yield of 100Mton but it was changed to lead to reduce fallout and so the aircraft could get away. This reduces the yield to 50Mton. So half of the energy would have come from these diety U-238 fission. If that change was not made 26% of all fallout from nuclear resting would have be produce by this test.
The practical thermonuclear weapon uses its outer U-238 layer because you can make a smaller and lighter bomb with the same yield.
So Tsar Bomba did result in a lot less fallout than you expect because it was an air blast and not a lot of energy was released from fission.
Most nuclear bombs aren’t designed or used in a way that creates a bunch of fallout.
Fallout is dirt and rubble that has been irradiated, pulverized, and dispersed into the atmosphere by a nuclear explosion. To create a lot of it outside of the intended target area and its surrounding radius, you need to have the explosion center on the ground. Doing so expels a lot of fallout into the air. But it also limits the explosive radius of the device itself. And that fallout isn’t able to be controlled once its in the air because so much force is behind it. Instead of only falling on the surrounding area, it gets swept into air currents. Dropping a bomb in that manner, you could accidentally direct lots of fallout to an ally, or yourself.
As a result, most nuclear weapons are designed to explode a few hundred feet in the air. This creates a wider explosive radius which destroys more target structures, and reduces fallout that enters air currents and spreads.
That’s not to say nuclear weapons wouldn’t cause other devastating issues in a live war. Firestorms are a major concern – you set off enough nuclear bombs in an area, and it creates a massive, self-sustained fire. Like a wildfire on steroids. This can spread well outside of the blast radius, burning everything, and releasing so much soot and ash that it could significantly lower earth’s temperature, the proverbial nuclear winter.
Two things are useful to know about fallout, for making sense of its environmental impact.
The first is that the amount of fallout is pretty much related to the amount of fissioning that takes place in the weapon. So the 50 Mt Tsar Bomba, for example, was only 3% fission (1.5 Mt) — the rest of its energy came from fusion. So it was much less inherently contaminating than, say, the first two US H-bomb tests (10 Mt and 15 Mt respectively) that had much higher fission fractions (80% and 68%, or 8 Mt and 10 Mt, respectively).
The second is that the height of burst changes where the fallout goes. If the fallout is low-enough to the ground (or on the ground), so that its fireball mixes up dirt and debris inside of it, then the fallout comes down pretty quickly, within a few hours. This is called “local fallout” and is responsible for those [really nasty fallout plumes](https://commons.wikimedia.org/wiki/File:Bravo_fallout2.png) that deposit a lot of fallout in a large — but still limited — area.
For bursts that are higher up, you only end up with what is called “global fallout.” The fallout stays in the cloud a lot longer and radioactivity comes out only after a much longer time has passed, and over a large area. So this distributes material further, but it is less intense (because it has time for the really nasty stuff to decay), and it is diluted (less material per square mile or kilometer). You get global fallout from surface bursts as well. For a big-enough bomb, [you can track its movement over the entire planet](https://pbs.twimg.com/media/DuKeeRbWoAEF7dQ?format=jpg&name=4096×4096). But this is much less intense: it is a measurable but small up-tick in global radioactivity, essentially.
So the Tsar Bomba was mostly fusion and detonated in a way where it did not produce local fallout. It did produce global fallout, which circulated in the upper atmosphere for several years before it all came down. But the fact that it stayed up so long meant that the contribution of that detonation to the radioactivity to life on Earth was negligible.
But there certainly were other big tests that were surface bursts, and some of them did create significantly radioactive areas that are still places where people shouldn’t live today. But that is all from local fallout, so it is much more limited to the test sites. So, for example, the Trinity test site in New Mexico, where the first atomic bomb was tested, is still somewhat radioactive today. You can visit it safely, and even work there safely, but if you had large-enough groups of people living there full-time, especially people who are in stages of life that are more sensitive to mutation damage (children, pregnant women), then you would expect to see some measurable up-tick in the cancer rate. It is similar to what the Chernobyl area is like; it’s not actually a radioactive wasteland, but it is a chronic public health risk to have large groups of people living there. (With small groups, you probably would not be able to tell if there were an y additional or “excess” cancers that were higher than the baseline expectations.)
Atmospheric nuclear testing certainly left _measurable_ effects — you can see isotopic signatures (like the so-called [bomb pulse](https://en.wikipedia.org/wiki/Bomb_pulse) of C-14) in things like wood and bone and other organic structures from this period, and it is a tell-tale sign that nuclear testing happened in the past. But measurable does not mean harmful. For people who were not directly downwind of the tests when they happened, the increase to their cancer risks is small enough that we can’t measure it (that doesn’t mean it doesn’t exist, just that it is a small “signal” compared to the cancers caused by other reasons, like smoking and pollution and diet).
As for the broader environment, the effects are even more elusive.
A useful effect of atomic testing. Stopping art forgeries. Atomic tests released isotopes in to the atmosphere that don’t appear in nature. All the great masters painted with organic materials. Test the paint with a spectrometer, find an isotope and you know it was made post 1945. Little useless nugget there
Not really, for two reasons.
1. Fallout from nuclear bombs actually decays very fast. Hiroshima and Nagasaki were resettled after a few weeks and nowadays the amount of radiation can barely be told apart from the normal background radiation. Chernobyl is still not settled, because the isotopes that are generated in a reactor are different and longer lived than those created in a nuclear explosion.
2. Fallout is only a big problem in high concentrations. If the fallout of a bomb is spread over a small area, it is problematic, but if it is spread over the entire world, it is barely noticeable.
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