Nuclear Power - Part 1

Nuclear power – we all know it's a source of incredible, almost unlimited energy. But it's kind of scary to think about, isn't it? Or is it? Let's take a moment to understand the physics and chemistry behind it before we all run for the bomb shelters.

“Nuclear” refers to the nucleus of an atom – its protons and neutrons. This nucleus is a positively charged ball of tiny particles. Now you know that opposite charges attract, and like charges repel; as in a magnet. So you'd think that magnetic force would just blow all those protons apart – and it would, if there wasn't something else holding them together. There is some energy holding it all together. Where does that energy come from? Well that's where things get a little weird.

Let's look at the nucleus of a Uranium-235 atom. It has 143 neutrons and 92 protons. A neutron has a mass of 1.0087 amu (atomic mass units), and a proton has a mass of 1.0073 amu. So the total mass should be 143x1.0087 amu + 92x1.0073 amu = 236.916 amu. But the mass of a Uranium-235 nucleus is only 235.0439 amu! There's 1.872 amu missing! That's like taking 100 blocks that weigh 1 lb each and building a castle with them, but the castle only weighs 90 lb. So where does that mass go?

Remember that E=mc². E is energy; m is mass; and c, to keep it simple, is just a number (about 300 million). What this means is that mass and energy are related. The missing mass has turned into energy, and that energy is being used to hold together the nucleus. This is what is known as strong nuclear force.

However, there are certain nuclei that are “unstable”, meaning that sometimes the strong nuclear force isn't strong enough to keep all that positive charge together. In these cases, magnetism will eventually win out and the nucleus will change to become more stable. There are different ways it can do this, but we'll focus on nuclear fission – when the nucleus breaks apart into smaller nuclei, creating smaller atoms. It turns out that since these smaller nuclei have less protons and hence less positive charge, they don't need as much energy to hold them together. When they are split apart, the energy that was holding them together is released and viola – you have nuclear power.

Now that you know the basics, stay tuned for next week when we'll discuss what it is about nuclear power that has everyone feeling so negative about protons.