Usually atomic bombs are composed of Uranium-235, Uranium-238, and Plutonium (if I am wrong, please correct me), all of which have an alpha decay. However, if alpha particles have the least penetrating power, and can be stopped through something a thin as a piece of paper, how is it so dangerous?
edit: Sorry for the confusion, I meant how is the radiation from it dangerous, not the initial explosion. However it seems my question has been answered on both accounts. Thank you to everyone who answered! I have a better understanding of it now.
In: 0
Because when they’re a bomb, they aren’t doing alpha decay.
It turns out, if you can force enough neutrons into the system, you can have some of those neutrons hit your fuel. Then that fuel breaks apart into 2 much smaller atoms, usually krypton, iodine, and other things around that size, in addition to 2 more neutrons. (And also in addition, it releases 1,000,000x the energy of a conventional explosion’s base reaction)
Now we started this with one neutron, hitting your fuel, and now you have 2 neutrons, each of which can hit another atom, which doubles the number of neutrons again, and this repeats in a chain reaction, doubling the number of neutrons, and doubling the released energy. After like a quarter second of this chain reaction, you’ll have “fissioned” quite a bit of your original fuel. And each fission reaction is more potent than any chemical reaction, so it’s not hard to make it be a very big bomb.
One way U-235 can decay to smaller bits is by ejecting an alpha particle. That is, as you said, not dangerous enough to make a weapon of mass destruction.
However, if you hit U-235 with a slow-moving neutron, it can split in a different way: basically shearing off into large clumps, and spitting off 2-3 new neutrons in the process: Eg, U-235 + n –> Barium-144 + Krypton-90 + n + n + heaps of energy; or U-235 + n —> Zircon-94 + Tellurium-139 + n + n + n + heaps of energy.
If those neutrons slow down to just the right speed (which can be arranged), then they in turn trigger more fissions, which trigger still more, so you get heaps of fission events, each releasing a lot of energy, packed into a very short period of time.
The thing that makes atomic bombs dangerous is
* the sudden release of truly enormous amounts of energy, and
* the production of a wide variety of radioactive isotopes that spread throughout the environment and ecosystem.
The energy vaporises everything in the immediate vicinity, sets fire to everything slightly further away, and causes a blast that smashes and burns everything further away still; there’s also a big burst of gamma radiation that causes its own set of damage to living things, and is very hard to shield oneself from.
The radioactive material consists of alpha, beta and gamma emitters (and their decay products), and these can each be dangerous in their own way. For example, even an alpha emitter can be dangerous if it becomes part of the food chain, and ends up irradiating people from the inside.
Alpha decay is irrelevant in a bomb. It happens once in a while but that’s not relevant for their use.
If the nucleus of uranium-235 or plutonium-239 gets hit by a neutron then it is likely to split into two smaller nuclei. The process releases a lot of energy: These two small nuclei are now very fast. They’ll heat up your bomb material. It also releases 2-3 new neutrons. They can then be captured by other nuclei, splitting them as well, releasing even more neutrons. That way you can get a chain reaction, splitting a significant fraction of your uranium or plutonium before everything flies apart from the produced heat. Each single reaction doesn’t release that much energy, but you can easily get 1000000000000000000000000 of these reactions, releasing a lot of energy overall.
To store bombs, the material is arranged in such a way that each reaction is unlikely to trigger another reaction. To explode a bomb the material is compressed, making it more likely that a reaction triggers another reaction, and then a few neutrons are shot into the material to start that chain reaction at just the right time.
Most of the damage comes from that initial release of energy, superheating the bomb and the surrounding atmosphere and producing a lot of radiation and a giant shockwave through the air. As side effect you also end up with various radioactive stuff – the atoms produced from the fission reaction, other stuff that captured a neutron and became radioactive due to that, and the remaining uranium or plutonium.
You get a mixture of alpha, beta and gamma decays from all that stuff. If people inhale that, or eat stuff contaminated with it, then it can decay inside a human body where alpha decays are a problem.
The majority of the damage caused by an atomic bomb has nothing to do with the radiation, it’s the energy involved.
E=MC^2 a tiny amount of mass converted into energy is A LOT of energy
A nuclear blast releases a lot of heat and produces a shock wave that can destroy buildings, and vaporize steel let alone what it does to humans.
People who survive a nuclear blast then have to deal with severe burns, possible blindness, and radiation exposure.
1. Fission and the natural decay chain are two different processes that create different products. For example, U-235 spontaneously decays into Thorium-231 by emitting an alpha particle, but in a fission reaction it splits into Barium-141, Krypton-92, and three prompt neutrons while emitting gamma radiation.
2. A piece of paper may be able to stop an alpha particle, but that doesn’t do you much good if the material emitting the alpha particles is microscopic dust specks contaminating everything in your environment. If it gets into the water supply, or is absorbed by food crops/animals, or if enough of it slips past your air filters, the radioactive material is going to end up inside your body where it’s impossible to shield against.
The question you’re asking here is kind of like asking, “How can forest fires be so dangerous if wood just rots over time? Compost piles don’t even get that warm.”
The mechanism that powers nuclear weapons has very little to do with alpha decay. Alpha decay is basically when a tiny fragment of the radioactive atom pops off. Like a button on a stretched piece of clothing. The atoms just do this at random sitting around doing nothing. This isn’t the part anyone is concerned about and doesn’t power the bomb.
What the bomb does is make the radioactive elements straight up rip themselves in half. That’s way more violent and energy-liberating than alpha decay and is where all of the terrifying power comes from.
Nuclear bombs are not dangerous because the cores emit alpha particles…. they’re dangerous because they create **massive explosions that can kill millions of people in an instant*.* That should really be self-evident.
As far as the specific radiation danger, the nuclear fission process changes the uranium or plutonium atoms into other isotopes like cesium 137, strontium 91, iodine 131 (and dozens of others that are *much more dangerous* than the original uranium and plutonium atoms, and the wind carries this as fallout and spreads them over vast areas.
Latest Answers