Nuclear fusion is a process that involves the joining or fusion of two atomic nuclei to form a larger nucleus. This phenomenon occurs under extremely high temperatures and pressures, typically found in the core of stars or in experimental fusion reactors. The process of nuclear fusion releases an enormous amount of energy.
To understand how nuclear fusion occurs, we need to consider the forces at play within the atomic nuclei. Nuclei are composed of positively charged protons and uncharged neutrons held together by the strong nuclear force. However, protons being positively charged experience a mutual electrostatic repulsion that tries to push them apart. This electrostatic repulsion is the reason why atomic nuclei must overcome a significant energy barrier to undergo fusion.
In stars, fusion reactions occur primarily between light atomic nuclei such as hydrogen isotopes (deuterium and tritium). The process can be described in the following steps:
Overcoming the electrostatic repulsion: The high temperatures and pressures in the stellar core provide enough kinetic energy to overcome the electrostatic repulsion between the positively charged atomic nuclei. At these extreme conditions, the atomic nuclei move with high speeds, increasing the likelihood of collision.
Approaching close enough: Due to their high kinetic energy, two atomic nuclei can approach each other closely, reaching a distance where the strong nuclear force comes into play. The strong nuclear force, which is a short-range force, can overcome the electrostatic repulsion at this close proximity.
Formation of a compound nucleus: When the atomic nuclei are close enough, the strong nuclear force can bind them together, forming a larger nucleus known as a compound nucleus. The strong nuclear force is stronger than the electrostatic repulsion within a certain range, allowing the atomic nuclei to fuse.
Energy release: During fusion, a small fraction of the mass of the reacting nuclei is converted into energy according to Einstein's famous equation, E=mc². This energy is released in the form of high-energy particles, such as photons (light), and is responsible for the immense energy output of fusion reactions.
It's important to note that achieving controlled nuclear fusion on Earth is still a significant scientific and engineering challenge. Scientists are actively working on developing fusion reactors that can sustain and control the fusion process for practical energy production. Successful fusion reactors have the potential to provide a clean, abundant, and sustainable energy source in the future.