(An Introduction To Fusion Energy)
By the year 2050, the earth is projected to be in turmoil. It is estimated that global greenhouse gas emissions will increase by approximately 50%, and the accelerated polar ice melt will result in numerous cities becoming submerged. These effects and much more will all occur because of climate change. And the leading contributor to climate change is the consumption of fossil fuels.
This is why we need to change. We need a better way to power the earth. One that is healthier for the environment and one that is able to work all the time, unlike solar or wind, which rely on certain weather conditions. This is where fusion comes in.
Quick History Of Fusion
The first time it was suggested that the stars generated their energy from the fusion of hydrogen into helium was in 1920 by a man named Arthur Eddington. However, it was not until later into the 1930s that a nuclear physicist named Hans Bethe clearly documented the process that Eddington suggested. Since then, there have been numerous breakthroughs in fusion, and it is projected to be usable in the next couple of decades.
Nuclear Fusion Reactions
Nuclear fusions are the reactions that power the Sun and Stars. This happens when two or more light nuclei merge to form one or more heavier nuclei. When combining these two nuclei, the resulting single nucleus's total mass is less than the two original nuclei's mass, and this leftover mass becomes energy. Einstein's equation (E=mc²) says that in part, mass and energy can be converted into each other.
The Two Forces That Allow This To Happen
The release of energy that happens with the fusion of light elements (Nuclei smaller than iron or nickel) is because of two opposing forces; the Nuclear Force and the Coulomb Force.
The Nuclear force combines protons and neutrons (nucleons) into atomic nuclei. This force is around 10 million times stronger than the chemical binding that holds atoms together in molecules. This allows nuclear reactors to produce about a million times more energy per kilogram of fuel than chemical fuel like coal or oil. The downside is that this nuclear force's range is extremely small, only a couple of femtometers.
( 1 femtometer is equal to 10 to the power of negative 15 meters (1fm=10-¹⁵m) )
The Coulomb force, also called the electrostatic force or Coulomb interaction, states three things:
- Like charges repel each other, and unlike charges attract. Therefore two negative charges repel one another, while a positive charge attracts a negative charge.
- The attraction or repulsion acts along the line between the two charges.
- The size of the force varies inversely as the square of the distance between the two charges. Therefore if the distance between the charges is larger, the attraction or repulsion becomes weaker and vice versa.
- The size of the force is proportional to the value of each charge.
How These Forces Work In Harmony
As you can see, these two different forces are doing opposite things. The Nuclear force is binding nucleons into nuclei, and because protons are positively charged, the Coulomb force causes them to repel.
Light nuclei are sufficiently small and proton-poor such that the nuclear force will overcome the Coulomb force. This is because the nucleus is small enough that all the nucleons feel the short-range nuclear force greater than or equal to the infinite range Coulomb force and, in this case, repulsion.
A great example of this happening somewhere close to earth is the sun. The sun is a main-sequence star, meaning that it generates its energy by nuclear fusion of hydrogen atoms into helium atoms in their cores. Every second the sun fuses 620 million metric tons of hydrogen into 616 million metric tons of helium.
On earth, scientists have been trying to replicate this process. It takes a lot of energy to create fusion. This energy can be created by heating the atoms of hydrogen to an extremely high temperature of around 100 million kelvin. This gives the nuclei enough kinetic energy to get close enough and fuse. The sun has a large enough mass that the gravity created by this mass crushes the sun inward enough to ignite nuclear fusion. We do not have this on earth, so we have to find a way to create an environment with sufficient temperature and pressure. There are generally two ways this can be done: Magnetic Confinement and Inertial Confinement.
Another thing to note about artificial fusion is that on earth, fusion reactors use deuterium and tritium instead of hydrogen. This is because this fuel reaches fusion conditions at much lower temperatures compared to other possible elements, and it releases more energy than other fusion reactions.
Like just mentioned before, we have to have extreme temperatures to create fusion. The problem with this is that there is actually no known material that can confine this hot plasma.
When we are heating the nuclei to extreme temperatures, we are what is called ionizing the nuclei, and creating a soup of nuclei, ions and electrons. This “soup” is what is called plasma.
Because plasma consists of ions, the nuclei in that plasma have a net electric charge. One really promising method of confining this plasma is a container that holds the plasma and guides it using magnetic fields. A key part of this process is that the plasma must be guided and moving in a helical or circular pathway. There are many different types of structures that allow this to happen, but right now, the most promising is the Tokamak.
Tokamak a Device for Magnetic Confinement
The Tokamak was initially developed by the Russians and was later perfected at Princeton. It is a toroidal-shaped device that uses different magnetic fields to keep the plasma nuclei moving in a circular fashion.
Inside of a Tokamak, one set of magnetic coils generates a “toroidal” field along the torus's length. What is called a central solenoid (a magnet that has an electric current) creates a second magnetic field along the “poloidal” direction (short way around the torus). These two fields combine to create a twisted magnetic field that confines the particles in the plasma. Finally, a third set of field coils generate an outer poloidal field that shapes and positions the plasma.
Inertial Confinement is another technique that tries to create fusion reactions by heating and compressing different fuels. To compress and heat fuel, energy is usually delivered using high-energy beams of laser light (electrons or ions). Generally, the fuel is in the shape of a pellet with a mixture of deuterium and tritium. Typical fuel pellets are the size of a pinhead and contain around 10 milligrams of fuel, and the fusion power is produced a few nanoseconds before the pellet blows apart. For this to happen efficiently, the time allotted for the pellet to burn must be less than the time it takes to blow up. This can be achieved by making the pellet radius reach over 3 grams per square cm.
Blue arrows represent radiation, orange is blowoff, and purple is inwardly transported thermal energy
The process for inertial confinement has four main steps,
- First, laser beams rapidly heat the surface of the fusion target, forming a surrounding plasma envelope.
- Second, the fuel is compressed by the rocket-like blowoff of the hot surface material.
- Next, the fuel core reaches 20 times the density of lead and ignites at 100 million degrees.
- And finally, thermonuclear burn spreads rapidly through the compressed fuel, returning many times the amount of input energy.
Companies Working With Fusion
We have now seen the basics of how fusion works and some methods used to try and produce fusion energy. Now let's examine some of the top companies in Fusion that are leading the industry.
ITER is an international nuclear fusion research and engineering project that is trying to build the largest fusion reactor. The total construction costs for ITER are estimated to be around 65 billion dollars, making it the most expensive science experiment in history. 35 nations are coming together to try and create the world's largest Tokamak. ITER will be the first fusion device to produce net energy and is projected to have its first Plasma in 2025.
General Fusion is a Canadian-based company that is developing a fusion power device based on magnetized target fusion. Their goal is to develop the first commercially viable fusion power plant that can deliver fusion in a clean, safe, and on-demand power at an industrial scale.
Founded in 2011, out of oxford, First Light Fusion is an international company that is diving deep into research about inertial confinement. FirstLight is also considering the costs and engineering practicalities of fusion when building the reactor and implementing its technology.
Common Wealth Fusion
CFS is an American company that is aiming to build a compact fusion power plant based on the ARC tokamak concept. Spun out of MIT’s Plasma Science and Fusion Center, they are in a unique position to deliver commercial fusion energy.
How This is Different From fission
When people say nuclear energy, immediately what comes to mind is nuclear power plants. It is true that both Fusion and Fission use nuclear energy, and both processes alter atoms to create power, however, the processes are contrasting.
To put it simply, Fission is the division of one atom into two smaller atoms, whereas fusion is the mixture of two smaller atoms into one larger atom.
The definition of fission is: the action of dividing or splitting something into two or more parts
Nuclear Fission happens when a large but unstable isotope (usually uranium-235) comes in contact with accelerated neutrons which causes the isotope to break up into smaller pieces. This creates two smaller isotopes and a large amount of energy. This energy is then used to heat water inside nuclear reactors and eventually create electricity. The two smaller isotopes that are ejected also become projectiles that create more fission chain reactions.
The huge thing that makes fusion better than fission is that when producing energy, there would be no radioactive waste, and it would produce energy much more safely.
Problems With Fusion
The promise of making our own energy sounds amazing. There are so many world problems that could be fixed with the usage of fusion energy. However, there are also a lot of difficulties. As you can probably guess, things can get extremely expensive. Like mentioned before, the start-up costs for ITER were around 65 billion dollars. Another issue is that all of this stuff must be happening in extreme heat, so things can get very complicated and very hard. Scientists have been making significant progress, but it is still far from working 100%.
Why Fusion Can Change The World
You now know how the basics of how fusion energy works, some of the techniques used to create artificial fusion, how fusion differs from fission, and some companies in fusion. I hope you can now appreciate how revolutionizing this technology will be once we will be able to make our own energy, without any of the environmental effects that other types of energy have.
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