Doesn’t fusion release energy, while fission requires it?
In: Chemistry
Not a nuclear physicist, but here is my understanding.
For fission, you normally have a nucleus that, if hit with a neutron, can absorb it and become another, very unstable isotope that will split in two on its own, releasing more neutrons and a lot of energy.
If on average, less than one neutron hits another atom and most exit your lump of material, you have a subcritical lump that will just sorta chill there.
If on average exactly one neutron hits, you have a critical mass that will sustain its own reaction. This is the state nuclear reactors balance in.
If it’s more than one, the reaction will continuously accelerate and basically you have a nuclear bomb. The principle there is to take two subcritical lumps, and jam them together, e. g. with explosives, to make a supercritical lump.
Overall, not much energy invested in starting the reaction itself.
Fusion makes use of the fact that, at temperatures and pressures like the core of our Sun, light nuclei will fuse together and make bigger nuclei, along with an even larger ton of energy than fission. Problem is, to achieve this first you need to actually get to these huge temperatures and pressures. Thermonuclear bombs do it by detonating a nuclear bomb around the hydrogen. For power plants, we’re kinda still working on it.
Overall, a lot of energy to start the reaction, but a whole lot more released by the reaction once started.
Latest Answers