An Introduction into Nuclear Fusion

Have you always wanted to learn more about nuclear fusion, but can’t understand the complex scientific writing? Well then you’re in the right place! In our posts, you’ll find plenty of information about nuclear fusion told in a way anyone can understand. But before we talk about all the cool things nuclear fusion can do, we have to understand how it works and what it does.

Nuclear fusion is a reaction which produces large amounts of energy by combining two hydrogen or helium protons (positively charged atoms), hence the term “fusion.” Fusion is not to be confused with fission, which is the opposite process. While fusion forms larger atoms out of smaller ones, fission splits larger atoms into smaller atoms. The energy released is primarily in the form of heat. Fission creates a large amount of energy, but also releases potentially dangerous radioactive byproducts. This “nuclear waste”  has to be collected and stored in safe facilities to ensure no leaks occur, which costs money and requires resources.  However, fusion releases even more energy, and does not release radiation. Also, hydrogen, which is used in fusion reactions, is the most abundant gas in the universe (Check it out here). Because it is such a sustainable source of energy, many people hope that Fusion will be the energy source for the future.

Fusion reactions combine different isotopes (same element but with a variation in the number of neutrons) of helium and hydrogen, including the Hydrogen isotopes Protium, Deuterium, and Tritium and the Helium isotopes Helium-3 and Helium-4. If the nucleus of the newly created nuclei needs less energy to hold it together than the old ones, energy will be released and mass will be “lost.” Different combinations of the hydrogen isotopes result in an isotope of helium and the release of high-energy particles, as shown in this fusion diagram.  However, since fusion brings two protons together, their positive charges cause them to repel each other. The only way to get protons to overcome this repulsion is to put them at extremely high temperatures and pressures.  In order for the protons to have enough energy to bond with each other, they need to be in an environment that is about 100 million Kelvins (six times hotter than the sun’s core). They also need to be under a lot of pressure in order to push them close enough together to fuse (1×10-15 meters away from each other). At first glance, these temperatures seem unreachable, as no known substance can withstand them.

To compensate for this fact and achieve these conditions, scientists use magnetic or inertial confinement reactors. A magnetic confinement fusion reactor contains plasma (superheated gas) which is spun with a magnetic field around the inside of the reactor so that the plasma does not touch the walls of the reactor. At the same time, the necessary pressure and heat comes from magnetic and electric fields themselves. An inertial confinement reactor (ICR) works differently. To compress and heat the fuel, energy is delivered to the outer layer of the target ( a pellet containing a mixture of Deuterium and Tritium ) using high-energy beams of laser light, electrons, or ions. The most common practice of ICR has used lasers. The heated outer layer explodes outward, producing a reaction force against the remainder of the target, accelerating the energy inwards, compressing the target. This process is designed to create shockwaves that travel inward through the target. A sufficiently powerful set of shock waves can compress and heat the fuel at the center so much that fusion reactions occur. However, due to current technological limitations, fusion reactions have to take place on a very large scale in order to achieve an efficiency high enough that the reaction will be productive.Fusion Diagram

With all these conditions required for nuclear fusion, do you think it could occur naturally? Where in the universe might these extreme conditions be present? Check out our next post to find out! Also, watch this video for a brief recap of the process discussed in this blog post.

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