Steps of nuclear fission:
- A slow moving neutron is fired at a uranium-235 atom.
- The uranium-235 atom then absorbs the neutron due to the fact the neutron is neutral and does not repel the atom's positive charge.
- The atom becomes unstable and gives out two lighter elements (two daughter nuclei) both of which are much smaller and possess less energy than the original atom. Two more neutrons are also released
- An example of two daughter nuclei the atom could release are krypton-91 and barium-143
- This process is called fission and releases a lot of thermal (heat) energy.
- The newly released neutrons can then go onto be absorbed into another uranium-235 atom and the process of fission is repeated.
This is what happens in a nuclear bomb, however, the process is not controlled and that's what makes it so dangerous compared to a normal bomb.
The daughter nuclei produced by nuclear fission have far too many neutrons to be stable, they need to turn one neutron into a proton. This also releases a beta particle at the same time.
Nuclear Fusion is the opposite of Nuclear Fission
It can only happen at very high temperatures and releases a lot of energy.
Two light nuclei (e.g hydrogen) are used to combine and create a larger nucleus.
Fusion does not leave behind a lot of radioactive waste and using hydrogen is practical as there's lots of it about in the air.
However, no material can withstand the high temperatures so the nuclear fusion reactors are very hard to build.
You have to contain the hot hygroden in a magnetic field
Most people wish that the theory of 'cold fusion' was true because it means creating electricity, easily and cheaply at room temperature.