Energy powers our world, homes, businesses, and practically everything we use on a day-to-day basis. That means that finding a cheap, safe, and high-power energy source is extremely important to advancing the world around us. As of now, coal remains the world's main source of energy. Finding a new energy resource to take coal's place - one that does not contribute carbon emissions to climate change - is also important. This is where nuclear energy comes in. About 11% of the world's power is generated from nuclear fission energy.
In simple terms, nuclear fission is when a heavy unstable nucleus splits upon impact with another particle, releasing energy. Uranium-235 is used in most fission reactions because, given that it contains 92 protons and 143 neutrons, it is an unstable atom. An unstable atom has an excess of either protons or neutrons. This causes the atom to be predisposed to reach a state where the protons and neutrons are much more balanced. When an additional neutron collides with this atom, it creates an even more unstable atom, Uranium-236. Because this atom is unstable, it almost immediately breaks into two more stable atoms - Barium-141 and Kronium-92, as well as emitting three additional neutrons. This process releases energy. Energy is released because the total mass of the products (the atoms created) is less than the mass of the reactants (original atoms). This means that the "binding energy" of the reactants is greater than the "binding energy" of the products, and that energy must be released.
Surprisingly, the three neutrons that are released during the reaction are the most important part of the reaction. This is because these three neutrons are able to collide with other Uranium-235 atoms in the reactor. This starts an entirely new fission reaction releasing energy and three more neutrons. Therefore, new nuclear fission reactions are continuously created, and energy is continuously released in a chain reaction.
The question arises - why exactly is nuclear fission energy a good power source for the world? Well, nuclear fission energy has high power output, is comparatively inexpensive, renewable, does not release air pollutants, and has a low carbon footprint. However, there are still problems with nuclear fission energy. The possibility of radioactive accidents and the long-term storage of nuclear waste often raise concern from the public. Past accidents from nuclear fission energy include the Three Mile Island accident in 1979, the Fukushima accident in 2011, and, the most damaging, the Chernobyl accident in 1986.
The Chernobyl accident occurred on April 26, 1986, when a nuclear fission reactor core in the Chernobyl Nuclear Power Plant in the Soviet Union overheated causing a steam explosion and fire. This incident and the following nuclear contamination are estimated to have killed between 4,000-90,000 people. This accident was largely caused by poor management of workers in the power plant, as well as a general absence of safety culture. These conditions led to the reactor core overheating and creating a huge steam explosion. The lack of a containment building over the reactor, as was used in reactors designed in the West, also contributed to the large scale spread of nuclear contamination.
Nuclear waste is also a major issue with nuclear fission reactions. The byproduct of fission reactions in a nuclear power plant is called spent fuel. Radioactive spent fuel from a reactor must be stored in a way that avoids any chance of people being exposed to radiation. This includes preventing contamination of water sources such as rivers or streams. Because this spent reactor fuel is very hot, thermally, it is first cooled in pools of water, then encased in casks of steel and concrete.
These past accidents and the fear of mismanagement of nuclear waste has led to changes in the safety protocols of nuclear fission reactors. Over the past years, nuclear fission power plants have been constructed to much higher standards of safety than they were at the end of the 20th Century. However, the public often still has concerns about the safety of nuclear power plants because of past accidents. As a result, in the past 20 years, only a few nuclear powerplants have been built in the United States. These public concerns are coupled with the low price of natural gas which makes the cost of constructing a new reactor a relatively more expensive source of electricity. In fact, the rate at which new nuclear power plants are being built is decreasing dramatically. For this trend to reverse, public education about nuclear energy and continually advancing safety precautions, including those related to the issue of nuclear waste, must continue to be developed.
Another possible source of nuclear energy is nuclear fusion. Nuclear fusion has been declared the "energy of the future." If we can successfully create energy from nuclear fusion, it will be extremely high-power and very safe.
So, what exactly is nuclear fusion? Nuclear fusion is a reaction in which nuclei of smaller atoms fuse together to create a bigger nucleus, releasing a large amount of energy. This process occurs naturally in stars, such as our Sun. Stars have temperatures in the thousands of degrees and this heat, combined with compression from intense gravity, fuse the nuclei together. Most reactions on stars occur with Deuterium and Tritium, the isotopes that make up Hydrogen.
When Deuterium and Tritium nuclei fuse together, the chemical reaction releases three products: Helium, a free neutron, and energy. Because the mass of the products is less than that of the reactants, energy is released. Mass cannot be created or destroyed. This means it must be converted into a new form, and that form is heat energy. Using the famous equation, e=mc^2, we can figure out exactly how much energy is released in any given fusion reaction. Over the past years, scientists have been able to recreate this process using high tech lasers.
However, the energy created by this process is less than the energy needed to start the reaction. What this means is that we are losing energy every time we accomplish a nuclear fusion reaction on Earth. For nuclear fusion to be a plausible energy source in the future, scientists must figure out a way to start a fusion reaction without losing energy in the process.
MIT and Commonwealth Fusion systems are working together right now to try to make energy efficient fusion possible and they hope to create a working fusion power plant within the next two decades. If they are able to create this fusion power plant, this type of energy is very likely to overtake other energy sources because it is safe, does not require the burning of fossil fuels, is energy efficient, and is significantly less expensive. According to researchers on the project, construction of the compact Sparc fusion nuclear reactor being developed by MIT and the school's supplemental firm, Commonwealth Fusion Systems, is expected to start in early 2021 and take three or four years to complete. The tennis court-sized reactor design uses newer high-temperature superconductor electromagnet technology and produces up to 10 times the energy it consumes.
