Radioactivity Study Guide

Nuclear fission and nuclear fusion are two distinct nuclear processes that involve changes in atomic nuclei, both resulting in the release of large amounts of energy. Fission is the splitting of a heavy atomic nucleus into two or more smaller nuclei, often initiated by the absorption of a neutron. This process releases energy, additional neutrons, and gamma rays. It is the principle behind existing nuclear power plants and atomic bombs. In contrast, fusion is the joining of two light atomic nuclei to form a heavier nucleus. This process requires extremely high temperatures and pressures to overcome the electrostatic repulsion between the positively charged nuclei. Fusion releases even greater amounts of energy per unit mass than fission and is the process that powers the Sun and other stars. While fission is currently harnessed for energy production, fusion research aims to develop a clean and virtually limitless energy source, though it faces significant technological challenges.

Nuclear fusion is the process by which two light atomic nuclei combine to form a single heavier nucleus, releasing a large amount of energy. This process powers stars. For fusion to occur, the nuclei must overcome a powerful repulsive force due to their positive charges. Protons within atomic nuclei are positively charged, and like charges repel each other. This electrostatic repulsion acts as a barrier, preventing nuclei from getting close enough for the strong nuclear force to bind them together. At low temperatures, nuclei have insufficient kinetic energy to overcome this electrostatic repulsion. At low pressures, the density of nuclei is too low, meaning collisions are infrequent. Therefore, extremely high temperatures (millions of degrees Celsius) and pressures are required to give the nuclei enough kinetic energy to overcome the repulsion and to increase the probability of collisions leading to fusion.