If you were to ask google what nuclear fusion is, you would get this result:
Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons or protons).
While the definition for all intensive purposes is correct, it is overly simplified and does not assist in building any deeper understanding. Let’s look at nuclear fusion here in more detail, and hopefully change that.
What is Nuclear Fusion?
Nuclear Fusion in the practical, real world sense is the smashing together of heavy hydrogen (Deuterium and Tritium) isotopes to form helium, as done in the sun, in an exothermic reaction where the mass lost is converted into energy, and MASSIVE amounts of energy are released. Einstein’s famous equation E = M(C^2) gives the amount of energy released from a given mass M when turned into energy as E, where C^2 is the square of the speed of light, an incomprehensibly huge number. A single D-T reaction, the fusion of one atom of deuterium and one atom of tritium as pictured below, releases 17.6 MeV for the consumption of
8.35*10^-27 kg of deuterium and tritium fuel, at a fuel efficiency 400 million times that of most fossil fuels and 4 times as efficient as the common nuclear fission used in nuclear reactors today. Fusion produces very little and very short-lived radioactive waste, is effectively 100% green, as it produces no greenhouse gasses and the fuels necessary are effectively completely renewable and very easy to obtain. Fusing just 42 kg of deuterium and tritium would be enough to power the US for an entire year, and would be almost 100% clean, if it were at all feasible. So, how do we make it feasible? There are many ways to achieve fusion, but the most promising methods demonstrated in recent science come from a trial of large scale D-T fusion in a small “artificial sun” (called a Tokamak reactor) done on January 10th, 2022 in China and a trial of small scale D-T fusion through a process called Inertial Confinement at the National Ignition Facility (NIF) on August 8th, 2021. We aren’t going to discuss Tokamak fusion here, as this article is already too long. To further a deeper understanding of Inertial Confinement Fusion, however, let's examine it in detail here. How does it work, how did its recent trial go, and what does that trial mean for the future of energy in our modern society?
How Does it Work? Inertial Confinement Fusion at the NIF
“Blast it with lasers” is what the scientists say when they attempt the process of Internal Confinement Fusion at the National Ignition Facility in Livermore, California, representing the most promising and currently most successful method of nuclear fusion within the scientific community to date. The NIF was primarily constructed at an experimental facility to examine the viability of fusion energy in a real fusion reactor using lasers to heat and compress hydrogen into extreme enough conditions for it to fuse. The facility uses a set of 3070 42-kg plates of laser glass – the strongest laser ever produced in human history – to heat and compress a tiny plastic bead (the size of a grain of rice, as pictured above) filled with frozen deuterium and tritium such that it could fuse. The bead is placed on a “target” of sorts, and then instantly hit with such a massive influx much heat and laser-energy that it instantly implodes due to massive external pressure. Imagine what would happen to a soda can if it got compressed by a sonic boom – this is like that but 100 times stronger. The laser compresses the plastic capsule around the fuel speeds of up to 350 m/s and raises its fuel's density by a factor of well over a thousand in a matter of trillionths of a second. Again, there is no human analogy which can express how extreme this process is. This radical compression and the influx of energy from the laser heats the plasma instantly raises the plasma to conditions that rival the core of the sun, heating it to hundreds millions of degrees, Fahrenheit or Celsius, while the center of the sun is only 15 million ºC, causing the plasma to instantly fuse and release massive amounts of energy. While this process only lasts for about 100 trillionths of a second before the plasma explodes, it should be enough to release massive amounts of clean, usable energy, in theory, due to the massive latent potential energy fusion is tapping into. So, what did scientists in the lab observe in practice?
How Did Its Trial Go? August 8, 2021
Unfortunately, what scientists observed in the lab was anything but “massive amounts of clean, usable energy,” a result which the researchers at the NIF actually expected due to the totally experimental nature of the project. The entire experiment generated a total amount of energy valued at just over 3 cents – only 1.3 megajoules or 0.366 kwh, enough to power an average American desktop for a couple hours or power an average American household for 1/80th of the day. This is not a large amount of energy, so what went wrong? Can fusion be something we look forward to as a clean energy source in the near future. The answer right now is no, and this article isn’t going to explain why because it's too long already, but I encourage you to do your own research – these concepts are fascinating if you get into them. In essence, the problem is that the technology isn’t there yet, and just powering up the laser that the scientists used 477 megajoules of energy, far outweigh the costs of what was produced for the sake of research in an experimental setting – again, read some articles about it, the simultaneous massive promise and total inviability of fusion energy is both interesting and a hoot. However, the achievement of fusion like this at the NIF presents a faint glimmer of hope that economically viable fusion might be viable in the future, and can motivate future scientists to study physics in order to theoretically make this alluring dream of practically viable fusion possible. Maybe someday, powering our society with the fusion of deuterium and tritium will finally be possible.
BIBLIOGRAPHY
“Fuelling the Fusion Reaction.” ITER, www.iter.org/sci/FusionFuels.
“How NIF Works.” National Ignition Facility & Photon Science, Lawrence Livermore National Laboratory. https://lasers.llnl.gov/about/how-nif-works
“Laser Glass.” National Ignition Facility & Photon Science, Lawrence Livermore National Laboratory. https://lasers.llnl.gov/about/how-nif-works/seven-wonders/laser-glass.
“Nuclear Fusion Power.” World Nuclear Association, Last Updated August 2021. https://world-nuclear.org/information-library/current-and-future-generation/nuclear-fusion-power.aspx
“U.S. Energy Information Administration - EIA - Independent Statistics and Analysis.” Use of Electricity - U.S. Energy Information Administration (EIA), www.eia.gov/energyexplained/electricity/use-of-electricity.php.
“What is a Tokamak?” ITER, https://www.iter.org/mach/Tokamak.
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