Science Series about Fusion: Part 1- Introduction to Fusion

Hello fellow Steemitonians and welcome to my first installment in the Science series where I will go deep into the science of various physics-related topics. The first topic I will cover is fusion, more specifically fusion power. This topic will be split up into four parts and today I will try to introduce the basic concepts behind fusion so we have some tools at our disposal for further digging into this topic.

To understand fusion we must first understand nuclear reactions which transform one element into another. We have all heard about fission. It is a reaction where a heavy nucleus breaks apart and forms 2 smaller nuclei and possibly fragments like neutrons, protons or electrons. We harness the power of fission in nuclear reactors which are widespread across the world by capturing the heat that is produced during the fission reaction. A typical fission reaction that is used in reactors is:

Here a neutron hits a Uranium nucleus which makes it unstable and causes it to split apart into Barium and Krypton. Additionaly 3 neutrons are released which cause further fission in the reactor in a cascade. This is how fission reactors work.

In all nuclear reactions the energy that is released is equal to the difference between ALL the final masses and ALL initial masses times the speed of light squared:

This means that for any process to be efficient in producing energy, masses of the elements after the reaction must be smaller then the masses before the reaction.

Typicaly in elements with larger nuclei (heavier elements), fission will occur while in elements with lighter nuclei this process will not occur as it is inefficient to divide a small nuclei even further. In fact it is much more efficient to clump smaller nuclei further together - this is what we call fusion!

In Figure 1 we can see the binding energy per nucleon of the nucleus for all known elements. The higher the binding energy per nucleon the higher the stability of an element. To deduce if fission or fusion is efficient for a particular element we must look at the trend of the line. If the binding energy of elements heavier than the considered element is higher, fusion is efficient because a nucleus created from a given element will be more tightly bound together - more stable. And vice versa. If the binding energy of a lighter nucleus is higher then that of a given nucleus this nucleus is likely to break apart.

_{Figure 1: Binding energy per nucleus of all known elements. The process of fusion is relevent when the line is rising and fission is relevent when it is falling. The line is neither rising not falling at element Fe - iron. This is the most stable element in the universe. Taken from [1].}

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To put it more simply if the line is rising at a given element it is efficient for that element to fuse - fusion. If it is falling it is efficient to break apart - fission. The steepness of the line also indicates the efficiency of a process. The steeper the line the easier it is to trigger the process. We see that the line is steepest at the lightest elements. This means it is easiest to fuse the lightest elements which are hydrogen isotopes. In fact the first reactors will fuse tritium and deuterium, which are isotopes of hydrogen. I will be talking about how we actually fuse these elements in the next installment of this series on fusion.

Ever since the start of the last industrial revolution that saw its birth with the propagation of coal as a power source, the need for a sustainable power source has grown. The first effect of pollution on our planet, and more specifically our climate, has been scientifically documented in the 19th century [2]. But not much attention has been devoted to this subject for another century. Only in the late 20th century scientists have achieved worldwide consesus that global warming as seen in the rise in global average temperature over the years is the consequence of pollution induced by human activities.

_{Figure 2: The clear rising trend of average global temperature, that seems to be speeding up in recent decades. Taken from [3].}

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One of the main polluters in the world is the energy production sector. In Figure 3 we can see how this energy production is distributed between different energy sources in the USA. We see that eventhough renewable sources and nuclear energy are on the rise they have not been able to keep up with the exponential growth of the worlds population. This means that eventhough sources like oil and coal damage the environment we have no other option but to use them without an alternative.

_{Figure 3: The distribution of different sources of energy production in the USA. Taken from [4].}

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But you might think: "What about nuclear power? That is pretty cool!" Well unfortunatelly eventhough nuclear power produces vast amounts of power its implementation is difficult and hazardous. The nuclear fuel is hard to obtain and difficult to store. And also, more importantly, the side products of nuclear power are highly radiocative, which make them unsustainable in the long term. Here is where I present to you the energy source of the future - fusion.

As stated before the fuel for the first fusion reactors will be hydrogen or some isotopical form. We are lucky in this regard, because hydrogen is the most common element in the universe and can be easily obtainable through catalysis of water. Thats right, everyday, plain and simple water. It can be salty or not. It does not matter. This is already a big plus for fusion as a power source. A non-toxic and readily available fuel!

As I will show in my next post not only is the fuel completely benign, the final products of the fusion reaction that will take place in fusion reactors are a neutron and helium. Already air consists of a few percent of helium which clearly indicates that helium will not be an issue when it comes to fusion as a power source. The neutron will be stopped in the reactor and its energy converted to electricity through heat. This means the neutron will not escape the reactor and is as such also a non-issue.

So what does this mean. In short. Fusion reaction as a power source is completely clean and its effect on the environment is zero! Also because the fuel is so common in the universe there is enough fusion fuel to power our civilization for millions of years to come. Literally!

This is my first part of my science series on fusion. I hope I convinced you that fusion is not only important but also neccessary as a power source for our ever-growing civilization. I also hope I have intrigued you enough that you will be waiting on thenext part which I will publish sometime next week. In my next part I will be talking about the technological hurdles that prevent us from utilizing fusion power right now and I will also show how far we have come in this important field.

If you like the content please upvote and follow me for future content. For more information on me or this series you can check the announcement of this series. If you want to know morea about me you can check my introduction post.

Images are linked to their sources in their description and references are stated within the text.

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