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Introduction
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From the cognitive revolution[“Cognitive revolution”, n.d] to the scientific revolution[“scientific revolution”, n.d], electricity, which exists as a form of important usable energy, was only an inconspicuous rock located at the bottom of the mountain of human history, until the 19th century[Harari, 2011, p.2]. Groups of elite theoretical scientists and experimental scientists carved this unexplored rock into modern surrealist sculpture, which pushed humans into the second industrial revolution immediately. Since then, the economic and industrial development was pushed from the country road into the highway. From commercial to military, electricity is almost omnipotent[“Use of electricity - U.S. Energy Information Administration (EIA)”, n.d], therefore the demand for electricity is limitless, and therefore we need a cheap but also environmentally friendly, high efficiency and powerful energy source, our only option in the future - Nuclear fusion energy. The reasons why I have chosen this subject for my topic are, first of all, I am personally a big fan of Physics, especially Atomic Physics(Nuclear Physics is a branch of Atomic physics). I believe I can explore more interesting information and knowledge during the writing and researching. Secondly, I already have a preliminary overview of nuclear physics. I believe it will make me feel more confident when I present my views and my thoughts to my readers.
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Principle of Nuclear Fission
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When a neutron(n 1) collides with a uranium-235(U 235) ( thorium-232(Th 232) and plutonium-239(Pu 239) are also in use, but much less) atom, it forces the uranium( thorium-232 and plutonium-239 ) atom to split into two atoms with smaller mass[Nuclear fission, n.d]:
If these reactions take place under precise conditions (heat/binding energy) with the critical mass, the nuclear chain reaction will initiate. The neutrons ejected away from the first reaction would have a possibility of colliding with another unreacted Uranium-235, triggering the second stage of the reaction. This is called the Chain reaction. The fuel will keep reacting until the remnant fuel is no longer suitable(heat/pressure/fuel condition) for reaction to maintain. All these processes which split atoms apart to get energy are called Nuclear Fission. During this reaction, a tremendous amount of energy from the nucleus is released. By splitting one atom apart by using 7~8MeV of energy on average, it produces approximately 200 MeV of thermal energy[Fission Power Explained, 2016], which we can then transform into internal kinetic energy of water(steam) to push turbines to generate electricity by using electromagnetic effects.
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Principle of Nuclear Fusion
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Nuclear Fusion combines atoms together by colliding them with high kinetic energy. Instead of using Uranium-235, Thorium-232, and Plutonium-239 as fuel for Nuclear Fission, Nuclear Fusion uses isotopes of Hydrogen or Helium atoms as fuel. They are Deuterium(D 2)(can be substituted by Helium-3(He 3)) and Tritium(T 3). When they collide with each other, they will form an atom with larger mass[“Fusion in brief”, n.d] [核聚变_百度百科, n.d]:
Energy is released during the reaction. Same as Nuclear Fission, Nuclear Fusion also initiates the chain reaction in precise (heat/density/time) conditions. Each time the atoms fuse, an amount of energy from the nucleus is released. The fuel will keep reacting until the remnant fuel is no longer suitable (heat/pressure/fuel condition) for reaction to maintain. Even though the energy released for each reaction of Nuclear Fusion is lesser than Nuclear Fission, however, Hydrogen atoms have less repulsive force to each other than Fission fuels. That means vast more hydrogen atoms can be contained in the same weight than Nuclear Fission. Therefore Fusion fuels are much more energetic than Fission fuels overall [Fusion In 30 Years?, 2019]. We can transform the thermal energy released into the internal kinetic energy of water(steam) to push turbines to generate electricity by using electromagnetic effects[核聚变_百度百科, n.d].
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Advantages of Nuclear Fusion (In compare to current power generation)
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Demerits of current electricity generation:
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Currently, the methods of generating electricity are fossil fuel burning(approx. Coal38%/Natural gas 23%), hydroelectric power(approx. 16%), solar power(approx. 2%),, wind power(approx. 2%), biofuel(approx. 2%), and nuclear fission(approx. 10%)[Electricity generation, n.d]. Sadly, their future, in my opinion, is pessimistic. This is because they all have their demerits, and they are very significant. The weaknesses of fossil fuel burning are, first of all, they produce too much carbon dioxide. And now, we have eaten the bitter consequences of excessive carbon dioxide emissions: global warming, air pollution, sea level uprising, etc. Secondly, the sustainability of fossil fuel burning is concerning. According to reliable sources, our known oil deposits could utterly outrun in 53 years; our known gas reserves only give us just 52 years left, and our known coal deposits could be gone in 110 years [Puiu, T, n.d] [The end of fossil fuels, n.d]. The problem is crucial. As for solar power, hydroelectric and biofuel, their sustainability is excellent, we could be sustaining them for basically-forever, and their environmental friendliness is also perfect. However, their efficiency is their biggest issue, which excluded them immediately from being the future major electricity generation. Nuclear fission has almost perfect sustainability and also efficiency. According to reliable sources, if the Nuclear Energy Agency (NEA) has accurately estimated the planet's economically accessible uranium resources, reactors could run more than 200 years at current rates of fuel consumption [Fetter, S, 2020]. On the other hand, nuclear fission power is one of the most efficient types of energy available today. An average capacity factor of 91 % beats all other energy forms by a substantial margin. Natural gas produces about 50 % whereas coal produces energy at almost 59 %[Electricity generation, n.d]. Wind power operates with a low 32 % efficiency[Electricity generation, n.d]. However, in the view of environmental friendliness, nuclear fission is improvable(but still significantly better than fossil fuel burning). As a byproduct during the nuclear fission, deadly radioactive residues, which are what we called-nuclear waste, could not be safely disposed of and extremely hard but must be contained in a specific container until it decays, and that would be millions of years. To make my point of view clear I would like to insert the data about the half-life for Uranium-235 and Plutonium-239, the fuel used in nuclear fission:
“All isotopes of uranium are unstable and radioactive, but uranium 238 and uranium 235 have half-lives which are sufficiently long to have allowed them to still be present in the Solar System and indeed on Earth. The half-life of uranium 238 is of 4.5 billion years, while uranium 235 has a half-life of ‘only’ 700 million years. [“Radioactivity: Uranium 238 and 235”, para.4]”
“Pu-239 has a half-life of 24,100 years and Pu-241's half-life is 14.4 years. Substances with shorter half-lives decay more quickly than those with longer half-lives, so they emit more energetic radioactivity. Like any radioactive isotopes, plutonium isotopes transform when they decay[“Backgrounder on Plutonium”. para 4].”
Since half-life is to decay half of its atom, theoretically they will never be completely decayed-until the last atom.
Some of the nuclear waste has a short half-life, for example, iodine-131[“Radioactivity: Iodine 131”. para.1]. But generally, the shorter the half-life, the more deadly it is(the average radiation emitted every unit of time is higher). But overall, the length of time is the biggest issue. To avoid harmful and long-life nuclear waste, and to increase sustainability and efficiency, the “upgraded version” of nuclear fission, nuclear fusion is our future.
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Advantages of Nuclear Fusion:
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As for all celestial bodies, nuclear fusion is their source of energy. It is the clean energy that feeds our Sun, and subordinately feeds all life on Earth. The same principle fits for all other stars and their civilizations(I believe aliens exist). Nuclear fusion is extremely powerful. Achieving nuclear fusion is like building a micro-version of the Sun on Earth.
Efficiency:
First of all, according to reliable resources, one kilogram of fusion fuel(deuterium, tritium,helium-3) could provide the same amount of energy as 10 million kilograms of fossil fuel [Advantages Of Fusion, n.d.]. Less than one tonne of fusion fuel will be needed for one Gigawatt fusion power station for one year.
Sustainability:
Secondly, the sustainability of nuclear fusion fuels is one of the biggest advantages in comparison to other power generation. According to reliable information from ITER, we can extract fusion fuel(isotopes of hydrogen) from seawater, and it could satisfy our need for millions of years [Advantages Of Fusion, n.d.]. Since there are so many isotopes of hydrogen in the ocean, humans will no longer be concerned about the fuel supply like fossil fuels, at least for millions of years
Cost:
Thirdly, the cost of generating electricity will significantly reduce, resulting in a decrease in the price of electricity in the market since they are no longer so scarce. When the technology is advanced enough, I believe that the electricity will eventually become worthless. Wasting power is no longer a concern [Advantages Of Fusion, n.d.].
Eco-friendliness:
Fourthly, nuclear fusion is completely “carbon-free” because the by-product of nuclear fusion is mainly helium and tritium. Helium is mostly harmless and tritium is radioactive. The good thing is that tritium decays very fast, and also much less radioactive as iodine-131, uranium, and plutonium. Their radiation is so weak that people use them to make fluorescence light bars. As long as you don’t inhale them, you are completely safe, the same goes for every other creature in the environment [Advantages Of Fusion, n.d.].
Safeties:
Fifthly, a Chernobyl-type of a nuclear accident is not possible in a tokamak fusion device. In comparison to nuclear fission, nuclear fusion is more sensitive to its fuel conditions. Once the fuel is too hot or too cold, or any other disturbance occurs, the plasma cools within seconds and the reaction stops immediately. The quantity of fuel present in the vessel at any one time is enough for a few seconds only and there is no risk of a chain reaction. Therefore, it is extremely safe [Advantages Of Fusion, n.d.].
All in all, nuclear fusion is the “ultimate energy source” for humans to develop. Its efficiency outruns any other present power generation; its sustainability outruns any of our present fuel supply; its cost will be much lower; it is eco-friendly, and its safeness is guaranteed. Under the background of rapid developments and expansion of our social, technology, industry and market. the need for electricity will quickly expand and eventually when our civilization is advanced enough, and the demand for electricity is unimaginable, nuclear fusion might be our only choice for our future power generation.
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Experiment and research progress
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Difficulties of making Nuclear Fusion reactor:
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Different methods of nuclear fusion:
The current mainstream controllable nuclear fusion methods mainly include magnetic confinement fusion [Magnetic confinement fusion, n.d], laser confinement (inertial confinement) fusion[How ICF Works, n.d], and ultrasonic nuclear fusion(bubble fusion)[Bubble fusion, n.d]. Magnetic confinement is to use a strong magnetic field to confine charged particles. We can construct a reaction chamber, then heat the fusion material to hundreds of millions of degrees Celsius to achieve a fusion reaction under magnetic confinement[Magnetic confinement fusion, n.d]. "At present, magnetic confinement fusion has been close to success under laboratory conditions and has become the mainstream research direction in the world[Magnetic confinement fusion, n.d].
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Tokamak reactor：
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The concept of magnetic confinement was proposed by Soviet scientists in the early 1950s and the first magnetic confinement was built in 1954. It was named the Tokamak reactor. The plasma is confined in this 'magnetic cage', like a hollow bagel. Through a special device, the fusion fuel of deuterium and tritium can now be heated to four to five hundred million degrees Celsius, and then a large number of fusion reactions occur at high temperatures. Therefore magnetic confinement fusion is also called the tokamak method[Machine, n.d].
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ITER(International Thermonuclear Experimental Reactor) project
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The ITER project, also known as the "artificial sun", is currently one of the world's largest and most far-reaching international scientific research cooperation projects. Its goal is to explore the fusion of science and engineering technology based on the peaceful use of fusion energy feasibility.
Today, the ITER program has involved China, Europe, India, Japan, Russia, South Korea, the United States, more than 30 countries and covers more than half of the world ’s population. It is the second-largest international science project after the International Space Station. It is also one of the largest and most far-reaching international scientific research cooperation projects in the world.
The goal of the ITER project is to jointly build a superconducting tokamak fusion test reactor in France. The project is divided into four stages: construction, operation, deactivation, and decommissioning. According to the deployment of the ITER plan, the construction phase is from 2007 to 2025; the operation phase is from 2026 to 2037, and the deactivation phase is from 2037 to 2042. As the world's first large-scale tokamak fusion test reactor, the ITER project requires a huge amount of engineering. The ITER tokamak device currently built near Cadarache in southern France will be 10 floors high, and the size of the first barrier outside the dewar that protects the extremely low-temperature components is equivalent to the Temple of Heaven[Fusion In 30 Years?, 2019]. The sensor system includes a total of 18 toroidal field coils, each one of them is about the same weight as the Boeing 747-400. An internal vacuum chamber is heavier than the Eiffel Tower in France. The whole device is still in the engineering construction stage, and it is expected to implement the commercial application of nuclear fusion energy around 2050[走近“颠覆性技术”, 2019].
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