The Basics of Fusion Energy
“Global warming isn’t a prediction. It’s happening.”
-James Hansen
We’re all aware of the implications of global warming, and we’re aware of the fact that a large contributor to this immense issue is the energy we use everyday. Yet, we aren’t changing our ways. It’s not that we don’t care. It’s not like we wouldn’t love to switch to some perfect, affordable source that would never run out or cause any harm. It’s just perhaps that we feel like we don’t have options, or rather, plausible options. Options that could power the world. If there was somehow an ideal, faultless choice at our fingertips, we would use it.
What if I told you this solution might already exist?
Here you’ll learn the basics of what fusion is by beginning with a brief foundational summary. Then we’ll look at how it works, covering the Coulomb and nuclear binding forces, and the difference between fission and fusion (what they are, and the difficulties of each). In the next section, we’ll discuss magnetic confinement reactors, exploring plasma devices such as tokamaks and stellarators, and inertial confinement reactors, where I will briefly write about an emerging alternative, fast ignition. We’ll conclude by talking about the benefits and downsides of fusion, as well as a quick outline of all the material we’ve learned.
What is Fusion?
To fully grasp the complex topic of fusion from all its angles, we first need to understand what exactly this energy is.
Simply put, fusion is the mechanism that powers the sun and stars. In the 1930s, scientist Hans Bete asked the question of if there was a way to somehow recreate this energy in a lab, which initiated the beginnings of research into fusion energy. Today, billions of dollars are being invested in the idea of generating the existing conditions within the centre of the sun on Earth.
How Fusion Works
The Coulomb force
Fusion occurs when light nuclei fuse — meaning combine or merge — together. In the sun, two hydrogen atoms must fuse together to create one atom of helium, liberating leftover subatomic particles and energy in the process.
It requires an abundance of energy to produce nuclear fusion. Atomic nuclei, comprising protons and neutrons, usually don’t want to go anywhere near each other. However, the Coulomb force (otherwise called the electrostatic force or Coulomb interaction, which states that like charges repel and opposite charges attract) is what prevents the two atomic nuclei from crashing into one another.
If these two atoms were set on a direct track to crash into each other, they would need to be put at incredibly high speeds so that when they would crash, the nuclear force (the force that binds neutrons and protons into atomic nuclei) would overcome the Coulomb force.
Strong Nuclear Binding Force
When fission or fusion happens, the strong nuclear binding energy of an atom is freed. The nuclear binding energy is the energy that is necessary to split apart an atomic nucleus into its protons and neutrons. By releasing this, fission or fusion can go towards doing things like producing electricity.
To make fusion, ionization must occur, which is done by heating the atoms of hydrogen to an exceptionally high temperature of about 100 million degrees. This way, they will have ample energy to fuse and be circumscribed so fusion can occur. The sun does this by gravity, but we usually do this on Earth by magnetic confinement, which we will talk about later on in this article. Before getting into the nitty-gritty of nuclear reactors, we first need to understand how they function.
Fission Reactors vs Fusion Reactors
Nuclear reactors broaden into nuclear fission reactors and nuclear fusion reactors, each of which will be further analyzed below.
Nuclear Fission Reactors
Unlike other energy sources, like fossil fuels and coal, nuclear plants do not burn anything to generate steam. A fission nuclear reactor is, essentially, similar to a huge kettle, if we want to take an analogy. It heats water to create electricity. These reactors split atoms (uranium atoms, specifically) to heat water into steam, which turns a turbine to create energy.
Nuclear fission reactors are designed to be composed of water surrounding solid uranium fuel. The reactor starts up, the uranium atoms split, and neutrons and heat are released. The neutrons clash with the uranium atoms, and they divide. This process repeats, causing more and more neutrons and heat to be produced. Steam is generated, which spins a turbine, which powers generators to yield electricity.
Nuclear Fusion Reactors
If you look up “nuclear reactors” on the web, you’ll find the large majority of articles are written solely about fission. That’s because fusion reactors are a lot newer and less developed. However, they’re emerging as a new technology because they are a lot more efficient and could provide many benefits. If we could get them to properly work, the impact would be monumental.
How is fusion different than fission? Fusion operates with much lighter elements than fission reactors. Two hydrogen atoms (the lightest element in the periodic table) in the sun must fuse to form helium (the second-lightest element in the periodic table).
Fusion reactors merge deuterium and tritium to create fusion fuel on Earth. This is much easier to manage than producing fusion using hydrogen because the energy is being conceived on a much smaller scale.
The deuterium-deuterium reaction is less regularly used than the deuterium-tritium reaction because its reactivity is much higher (approximately 20 times) and performs at a lower temperature. However, tritium is incredibly rare in nature due to its isotope’s short life, therefore this usage can be difficult.
Which is Better?
Although fission reactors may be simpler to run, they are more dangerous because they release gamma emissions which can cause cancer. In large amounts, the impact could be fatal.
Like the nuclear fission power plant, a fusion plant would not release greenhouse gases and would not require the burning of fossil fuels. Its fuel (isotopes of hydrogen, most of the time) would be far more abundant than the uranium generally used in nuclear plants, while also producing less radioactive waste.
Nuclear fusion may seem like the perfect option, but it is much more difficult to make function compared to fission, and again, much less developed. Despite some individuals believing fusion reactors are impractical because of this, there are feasible designs being built to change the world by companies such as Tokamak Energy, AGNI Energy, Commonwealth Fusion, General Fusion, and ITER. If you want me to write an article on any of these businesses (or all of them) let me know in the comments! We will be talking a bit about ITER in the next section.
Magnetic Confinement
As we’ve talked about earlier in this article, certain temperatures and pressures must be reached for hydrogen fusion to take place. There are two ways to achieve this goal — magnetic confinement and inertial confinement.
Let’s start with magnetic confinement.
Magnetic confinement heats and squeezes hydrogen plasma through magnetic and electric fields. A stream of hydrogen gas is heated by neutral particle beams, electricity, and microwaves, which changes the gas into plasma.
The plasma proceeds to be compressed with magnets, which is when fusion begins. The most practical shape for this plasma is a toroid, which resembles a donut shape.
Tokamaks
A donut-shaped reactor like the image above is a tokamak. Tokamaks are very powerful machines that are used to magnetically confine plasma in the shape of a torus. Inside of these devices, there is severe heat and pressure, causing gaseous hydrogen fuel to become plasma.
ITER is one of the most enormous, if not the most enormous, fusion energy project in the world. They are using the method of magnetic confinement, and they are using a tokamak. To further expand our understanding on this topic, we can take a look at how ITER’s fusion reactor functions.
The fusion reactor begins by heating a stream of deuterium and tritium fuel to produce hot plasma. It then squeezes the plasma so that fusion occurs, and this reaction causes the lithium blankets surrounding the plasma chamber to absorb neutrons, which produces more tritium fuel and heat. This heat gets transferred to a heat exchanger to create steam, which drives turbines to create electricity. The steam then gets condensed into water to repeat the process of absorbing more heat from the reactor.
Tokamaks do have downsides, though. Since a transformer can only drive currents in short pulsations, currents in the plasma fluctuate unpredictably. Some disruptions can be more harmful than others, at times even going to the extent of damaging the reactor.
Tokamaks have always been used as the powerhouse designs of fusion, as they are solid, symmetrical, and simple to engineer, but stellarators are emerging as a new and exciting fusion device.
Stellarators
Stellarators are similar to tokamaks in the objective they are trying to achieve, however they function differently. Tokamaks have always been considered the best option out of the two because they are better at trapping gas and heat — but the donut-shaped design is composed of windings of wire looped close together inside the hole of the doughnut, which makes the magnetic field strongest in the middle and weakest at the rim.
Because of this disproportion, particles tend to shift and hit the barrier. The stellarator varies in that there is a twist in the design, which pushes particles through high and low magnetic fields, hence removing the disproportion.
Stellarators are advantageous because their fields are rooted in external coils that do not require pulsing, hence they maintain a steady state instead of abruptly faltering like tokamaks. The downside here is that they are incredibly difficult to build.
How do stellarators work? Since the gas cannot be held in a normal vessel (due to the extreme heat of about 100 million degrees), it is contained within a magnetic cage. The heat robs electrons from their atoms so that a plasma of electrons and ions remains. Due to the maximal temperature and pressure, the ions speed up, overcome their forces of repulsion, and fuse.
The graphic below shows the design of a stellarator. Wendelstein 7-X is the first large-scale optimized stellarator in the world, therefore we will use this as an example.
Inertial Confinement
Inertial confinement squeezes and heats hydrogen plasma by using laser beams or ion beams. In an inertial confinement fusion reactor, there is a tiny pellet usually of deuterium-tritium fuel that is compressed at a large density and temperature. Fusion power is generated in the very minimal amount of time there is before the pellet explodes.
There are usually only a few milliseconds for this to occur. The pellet radius must reach over 3 grams per square cm in order for the pellet to burn in a lesser time than it takes for disassembly. This compression happens by focusing a laser beam or particle beam toward the pellet — there must be a high mass density and a large density to achieve a lengthened burn and a decreased disassembly time. For an inertial confinement reactor to work, there must be a pellet gain of at least 100. A pellet gain is the ratio of driver energy (the laser beam or particle beam) to the fusion generated.
Fast Ignition
Fast ignition is an emerging alternative to inertial confinement, as it is more efficient in the sense that the driver energy is drastically reduced. The energy used to heat the fuel comes from another laser (versus implosion used in inertial confinement, which takes a lot more time). The laser beam compresses the fuel, and another laser proceeds to pulsate small segments of heat from the fuel to very high temperatures until it reaches fusion temperature. If you would like me to write an article with a further description of how this works, let me know!
Pros and Cons
The Benefits
Scientists have been working relentlessly at fusion for years because of the colossal impacts it could have if it is successful. We would get an infinite and abundant energy source, one which could fuel the world for hundreds of millions of years. There are no deficits environmental-wise, either. Fossil fuels have deleterious effects on the Earth, as most people know, but a lot of clean energies (like solar, for example) give off greenhouse gases or produce combustion products, which fusion does not do.
A fusion power plant is also relatively safe — because the output of helium and neutrons is not radioactive, long-lived radioactive waste is not generated and there is no chance of a meltdown. Although building power plants will be costly, the price of fusion will actually even out to be of equal expense compared to the sources we use currently. Lastly, unlike other energies, fusion can be produced on demand, as it is not influenced by the weather.
The Downsides
The advances of fusion have been slow and difficult over the years. Many individuals have skeptical perspectives on the topic — it simply seems too good to be true, having not lived up to its potential, remaining somewhat unsolved and elusive. Are we getting our hopes up for no valid reason?
Achieving fusion is no simple task, as it requires heating, compressing, and confining hydrogen plasmas at extreme heat. A very popular fusion reaction is deuterium-tritium fusion. This uses the lowest plasma temperature to generate large amounts of fusion power out of all types of fusion.
However, the core of the reactor can still require up to 200 million degrees, which is very hot, to say the least. There’s not much we can do about this, though. High temperatures are a necessity for fusion. If we tried to perform the task at low temperatures, the fusion power produced would be substantially small, regardless of the amount of fuel used. This is a prime difficulty within fusion energy. Currently, there has been technology designed to create powerful magnetic fields, but this is not yet advanced enough to fuel the world. We’re close, though.
As mentioned previously, the initial costs for fusion are very expensive, this denoting the scientists, experts, and facilities needed, not to mention the construction of the power plants. That being said, we’ll probably save more money in the long run because of the resources and biodiversity that fusion will prevent from being destroyed.
The final big challenge concerning fusion energy is the energy input vs energy output issue. The immensely high temperatures that are crucial to fusing two nuclei of the atoms together consume a vast amount of energy, close to the amount being produced. With time, more efficient methods and strategies will most likely be discovered, but for now, this remains a problem.
A Summary of What We Learned
We’ve looked at a lot in this article! Let’s sum it up in some bullet points.
- Fusion powers the sun and the stars, which we are trying to recreate on a smaller scale in a lab
- Fusion is when two particles merge together to form one nuclei
- It requires a vast amount of energy to create fusion
- Fusion is generated in nuclear reactors
- Nuclear reactors can fall under the category of fusion reactors or fission reactors — fusion reactors operate with lighter elements than fission reactors and would be safer, but they are far more difficult to run
- To achieve high temperatures and pressures in a nuclear reactor, magnetic or inertial confinement can be used
- There are two types of plasma devices, tokamaks and stellarators
- Fast ignition is an alternative to inertial confinement because there is decreased driver energy and hence is more efficient
- Fusion would be abundant, safe, environmentally friendly, affordable, and would be able to be produced on demand
- Progress has been slow over the years, and it is difficult to produce fusion because of the high temperatures it requires, as well as the energy input vs output and the high initial cost
Fusion has the potential to change the world. This energy could be life-changing. It could give us an answer to global warming. Stay informed.
If you want to learn more about fusion, check out these resources. If you have any questions, feel free to contact me through the comments!
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