Question: How is nuclear energy produced?

James Smallcombe answered on 18 Jun 2020:

Nuclear energy relies on the formula E=mc^2, that is mass is equivalent to some energy. Different nuclei have very slightly different amounts of binding pulling them together from the “strong nuclear force”, which causes them to have different masses, larger than the sum of the masses of the particles that stick together to make them. The binding energy actually gives them extra mass!

In a typical nuclear fission power plant very heavy but weakly bound (not much of the mass comes from binding) uranium absorbs a neutron, the energy from catching the neutron gives the uranium just enough energy to split. It breaks into 2 smaller pieces (and a couple more neutrons that carry on the reaction). The total mass of the smaller pieces is actually higher than the original uranium, and the mass difference is released as energy to make the pieces move faster. These pieces “moving quickly” is what we usually just call heat.

So the last step is simply that this is happening lots of times inside a reactor making it very high temperature and we use that heat to boil water and run steam turbines, the same as at a gas or coal power plant, but without burning fossil fuels and making CO2.

There are other less common and experimental (fusion) ways but they all rely on the mass energy equivalence and nuclear binding energy.