The Quest for Self-Sustaining Power

"What is Nuclear Fusion? How does it work?" - Self

Extreme science has always been an interest to me, especially the grand implications that can be achieved by studying it. Nuclear fusion - or harnessing the power of the sun - has some of the grandest implications, being able to power the entirety of New York City with just 20 grams of hydrogen. (which is about as much as one 50L tank of hydrogen that research facilities use). It's such a remarkable technology, that it has been placed on the Grand Challenges for Engineering and has made much headway thanks to breakthrough research from MIT, as well as continuous research from nationwide research facilities in Japan, France and America.

So what is fusion anyways? Going off the more well known idea of Chinese-American culinary fusion, it is the idea of taking two things and pushing them together. You see, there is a lot of energy packed into the nucleus of an atom and, when two atoms are shoved together to make something new, a lot of that energy is released to make room for all of it. In nuclear fusion, we take two hydrogen atoms (specifically, a special isotope of hydrogen called deuterium and another called tritium) and mash them together to make a helium atom and a spare neutron.

Looks simple, doesn't it?

Now, this might look like an easy process, but mashing together two hydrogen isotopes isn't like baking a cake. Atoms naturally push each other away. While atoms are electrically neutral, they do still have a positive side and a negative side. Unfortunately, the positive side is the core (nucleus) and the negative side is the shell (electron cloud). If you've ever tried to push two similar poles of a magnet together, you'd see the problem here. In order to accomplish fusion, you need to push atoms together so hard that their electron clouds overlap and their nuclei crash into each other. That's a lot of energy.

On the left side of the graph, all of that energy is just overlapping the electron cloud, the nuclei aren't even close yet...

However, once we get the nuclei to crash together, fusion is a pretty quick next step. But how do we overcome all that repulsive energy? Well, the atoms just need a little motivation. If you give them the energy they need to push through the electron cloud, they will do it all by themselves. Atoms move naturally when they're heated up. The hotter they are, the faster they move. When they bump into another atom, they change directions. However, if you make them hot enough, they will hit the other atoms with such force that the nuclei will collide and they will fuse. So if you want to get some fusion, you have to put in a lot of energy. How much energy, you ask?

A lot...

In order to start a fusion reaction, several lasers are fired at a piece of deuterium (remember: hydrogen isotope), which will require about 800 Megawatts of energy (equal to about 80,000 LED lightbulbs). This is a very difficult feat, and a huge cost to start the reaction. However, the great news is that once the fusion reaction begins, it's self-sustaining. The energy released from the reaction is recycled to activate it again. Additionally, the extra neutron released is added to a deuterium to make the tritium required to start it. So you only need a pool of deuterium and the energy required to activate it, and you have an excellent source of power.

But what is deuterium? If you pull out your handy Pocket Periodic Table of Elements, you won't find it on there because it is an isotope of hydrogen, meaning that it is a hydrogen atom with an extra neutron. A normal hydrogen atom is one proton and one electron (no neutrons). But sometimes, a hydrogen atom can pick up an extra neutron, like picking up a hitchhiker on the side of the road. It doesn't happen often, but it does happen. Most deuterium in the world comes from the oceans, but it's still only 0.0156% of all the hydrogen atoms found in the ocean. That might not seem like a lot, but it's still hundreds of lifetime supplies. Additionally, through some pretty awesome science, it can be made from ordinary water.

So if we have the materials and have the technology and can produce the energy, why aren't we all running of fusion power now? The main challenge is to make a machine that can withstand the absolute onslaught of abuse. For nuclear fusion to occur, we must heat the hydrogen up to about 100 million Celsius... Materials usually can't handle that kind of heat. Additionally, the neutrons flying about from the reaction can also do some damage and leave some pretty heavy radioactivity to clean up.

Radioactivity, you say?

So is it safe? Many people hear nuclear energy and automatically jump to the worst case scenario (i.e. Chernobyl or Fukushima). To start, nuclear energy itself is not a dangerous thing and can be well contained, albeit requiring a serious amount of time to cool down. Fusion energy is even safer, as a leak would immediately cool down to temperatures that inhibit the fusion reaction, stopping it in its tracks. There is still radioactive material to deal with, but nowhere near the level that normal nuclear fallout would produce.

Every year, countries are making new advancements in sustainable nuclear power, testing new technologies and alternative theories to make it safer, cheaper and easier to maintain. It might still be on the Engineering Grand Challenges, but it won't be for long and nuclear fusion will be the be all, end all of energy production. Just make sure to send your thank you letters to the sun for giving us the idea.