Nuclear reactions of fission and fusion lie at the heart of modern energy generation and the understanding of the universe’s fundamental processes. Fission, the splitting of atomic nuclei, powers nuclear reactors, providing a substantial portion of the world’s electricity. On the other hand, fusion, the combining of atomic nuclei, fuels the sun and stars, offering the promise of virtually limitless clean energy on Earth.
Today we will understand why some elements undergo nuclear fission reaction while other undergo fusion reaction to form heavy element. It has to do with a curve in nuclear physics we call the binding energy curve. Where the Binding energy per Nucleon is plotted versus the Nucleon number (Mass of the element).
Binding Energy Curve
Binding energy is the energy required to break the nucleons (proton and neutron) apart. But for us it is actually the measure of stability of the nucleus. Larger the binding energy per nucleon, the more stable the nucleus is and the greater the work that must be done to remove the nucleon from the nucleus
Points to be noted from the graph
- The maximum binding energy per nucleon occurs at around mass number A = 50, and corresponds to the most stable nuclei. Iron nucleus Fe56 is located close to the peak with a binding energy per nucleon value of approximately 8.8 MeV. It`s one of the most stable nuclides that exist.
- Nuclei with very low or very high mass numbers have lesser binding energy per nucleon and are less stable because the lesser the binding energy per nucleon, the easier it is to separate the nucleus into its constituent nucleons.
The presence of a peak in the binding energy curve around the stability region near iron has significant implications. It enables the occurrence of nuclear fusion in light nuclei, where under specific conditions, these nuclei combine to form a final product with a higher binding energy per nucleon. Example of such a reaction is
2H (deuterium) + 3H (tritium) -> 4He (helium) + 1n (neutron) + 17.6 MeV of energy
Nuclear fission is the process where the nucleus of an atom splits into two or more smaller nuclei, along with the release of a large amount of energy. One of the most well-known examples of nuclear fission is the fission of uranium-235 (U-235) by absorbing a neutron, which results in the formation of two smaller nuclei, typically krypton-92 (Kr-92) and barium-141 (Ba-141), along with additional neutrons and a significant amount of energy.
U-235 + 1n (neutron) -> Kr-92 + Ba-141 + 3 1n + Energy
As we delve deeper into the mysteries of the atomic nucleus, we can anticipate even more remarkable discoveries and innovations in the future. Nuclear physics will continue to play a pivotal role in addressing our energy needs, exploring the origins of the universe, and advancing our knowledge of the fundamental forces that govern our world. So, stay tuned for exciting developments in the ever-evolving realm of nuclear physics, where the quest for knowledge and the pursuit of practical applications will lead us to new frontiers of understanding and potential.