I understand that an atomic bomb works by detonating fuel (uranium or plutonium) that sparks a chain reaction of fission so every atom causes the fission of more atoms until the fuel is used up. But I don’t understand 2 parts of this process:
1. Why does the fuel (uranium atoms) blow up? I see some sources saying the atoms are being split, but other sources say atoms are being smashed into each other. Which is it? And why does performing that action cause an atom to violently explode?
2. Once the fission is happening and growing exponentially through the fuel, why doesn’t it set off a chain reaction with the atmosphere? Why exactly can’t uranium spark the fission of nitrogen? Why does the chain reaction stop when the uranium is gone?
I know other atomic bomb questions have been asked, but in my research I couldn’t find these answers. Thanks so much!
In: Chemistry
Fissile fuel (uranium or plutonium) has atoms that sometimes naturally split apart by themselves, releasing energy and neutrons. Those neutrons can make other fuel atoms also split apart, leading to a chain reaction which produces heat. This only happens if there is enough fuel in one place (this is called a critical mass), so the bomb has a mechanism to transform a subcritical mass into one that blows up. All modern bombs use regular explosives to squish a ball of plutonium so hard it blows up. The immense heat from the chain reaction turns the bomb and its surroundings into a giant incandescent ball of plasma.
Modern hydrogen bombs actually use a very small plutonium core, and use the heat from that explodig to smash hydrogen atoms together. When hydrogen atoms fuse, enormous amounts of energy is released (this is what makes the sun shine, after all) making for a much bigger explosion. The hydrogen reaction also makes neutrons, which makes more of the plutonium react, further increasing the yield. In the first atomic bombs, less than 10% of the fuel had time to react before the bomb blew apart.
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