Now that we have taken a look at the brutal power of fission, lets take a look at its younger sibling. Nuclear fusion is a much newer idea than fission. It is not yet done on a large-scale and we cannot harness its energy properly, but it shows potential to be more useful, safer and easier than fission, so what is it?
Well in fission, we take one heavy thing and split it in two. Fusion is the opposite. We take two very light particles and push them together to make a new one.
The two particles we push together are called deuterium and tritium. They are different isotopes of hydrogen, in other words, they both have one proton, making them hydrogen, but they have different numbers of neutrons. Deuterium has one, and tritium has two. Pushing them together is difficult. The glue of neutrons only works when the particles are touching, but the protons repel each other larger distances. But once they get very close, the neutrons grip on and energy is released.
Once the atoms have gripped onto each other, an entirely new substance is made, Helium. Helium has two protons and two neutrons, so we have an extra neutron which is released:
So how do we get the atoms to fuse? In the same way that we do a great many other things in physics, with giant lasers! The deuterium and tritium are packed together into a tiny pellet about 4mm in diameter. On the outside you have a simple containing layer and then you have different forms of the DT (deuterium and tritium) mixture, either ice or gas. Now comes the lasers.
The outside layer of the target is heated to very high temperatures using the lasers(1). Eventually the temperature becomes so high that the outside shoots off. Due to Newton’s third law, every action has an equal and opposite reaction, the rest of the target is pushed inwards with an incredible amount of force(2). It compresses to about a 16th of it’s original size, to a diameter of 1/4mm(3). This compression leads to a rapid heat increase and the reaction starts, at this point the density at the core is 20 times that of lead and is 100,000,000˚C(4). Though the initial power input is very high, the energy that we receive from the reaction is much more.
This method is much nicer than fission. It is more efficient, does not create any radioactive byproducts and if the reactions starts to get out of hand, can be shut off immediately with a flick of a switch.
So why don’t we use it? Because it isn’t as easy as fission. The supply of uranium you have in a fission core lasts a year. On the other hand, the reaction in a fusion core takes place within a few minutes and then a new target needs to be put in and the reaction initiated again. Seeing as each of these reactions don’t release very much energy on their own, we need to be doing thousands a day and currently our facilities just aren’t ready for that.
Nuclear power is an incredible thing. The fact that we have managed to harness energy we did not know existed until within the last century or two amazes me. However, right now it is not capable of being our main new source of energy. Though we can control fission quite well, events like Chernobyl mean that the public feel threatened by it, and though fusion is almost the perfect energy source, we cannot yet harness it well enough. So watch this space, as our technology improves, nuclear power will become safer and easier. The futuristic image of nuclear energy powering the world is just around the corner.
We hope you’ve enjoyed this post! Check out the first half of this post series on nuclear power.
If you did like the post then please check out our last two posts:
Matter and Antimatter: Why hasn’t the whole universe exploded? – When they come together, matter and antimatter explode, so why hasn’t that happened to the whole universe?
What is Graham’s Number? – Sometimes we need really big numbers in maths. We aren’t talking a million, a billion or even a trillion. No, this is the largest number ever used in a mathematical problem, and saying it was big would be an understatement.