How does the metal ball used in nuclear weapons work, and how can it be handled without constant fear of exploding?
In: Technology
you’re probably thinking of the plutonium core. plutonium is a fissile material, which means when a neutron hits a plutonium atom’s nucleus it will split, releasing energy and more neutrons, some of which may hit other plutonium atoms and cause them to split as well. the core is subcritical, which means this reaction isn’t self-sustaining. not enough atoms will be hit in order to keep the reaction going.
you can increase the number of atoms that split by surrounding the core with neutron reflectors or by compressing the core and packing the atoms closer together. when the reaction is fast enough that it sustains itself at a steady rate it’s called critical, and when it begins to accelerate that’s called supercritical
a nuclear explosion requires the core to be so supercritical that most of the atoms in the core are consumed in a tiny fraction of a second, releasing all of that energy in an instant. it takes very specific conditions for that to happen. in old nuclear bombs like the ones dropped on Japan, they achieved those conditions either by pushing two pieces of fissile material together (the gun method) or by using a shell of explosives to compress the core down until it was dense enough to cause the required reaction (the implosion method) [like this](https://upload.wikimedia.org/wikipedia/commons/thumb/c/cb/Fission_bomb_assembly_methods.svg/800px-Fission_bomb_assembly_methods.svg.png)
the faster the reaction, the more heat and radiation is released, so a core can be dangerous if it’s used improperly and allowed to go supercritical, but there’s no way for it to cause a nuclear explosion outside of very specific circumstances that will never occur outside of the nuclear bomb itself. that’s why you don’t need to worry about nuclear power plants exploding like nuclear bombs
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