What distinguishes nuclear fission from nuclear fusion?

Nuclear fission involves splitting a large nucleus into smaller ones, while nuclear fusion combines small nuclei to form a larger one.

Nuclear fission and nuclear fusion are two different types of reactions that release energy due to the changes in the nuclear structure of atoms. In nuclear fission, a heavy nucleus, such as uranium or plutonium, is split into two or more smaller nuclei, along with a few neutrons and a large amount of energy. This process is typically initiated by the absorption of a neutron by the heavy nucleus. The resulting fragments are usually unstable and undergo further decay, releasing more energy.

On the other hand, nuclear fusion is a process where two light nuclei, typically isotopes of hydrogen like deuterium and tritium, combine to form a larger nucleus, such as helium. This process also releases a large amount of energy, but it requires extremely high temperatures and pressures to overcome the electrostatic repulsion between the positively charged nuclei. This is why nuclear fusion is the process that powers the Sun and other stars, where such extreme conditions exist.

While both processes release energy, they do so in different ways and under different conditions. Nuclear fission is the process used in nuclear power plants and atomic bombs, while nuclear fusion is still largely in the experimental stage for power generation on Earth, due to the difficulty in creating and maintaining the necessary conditions. However, fusion has the potential to provide a nearly limitless and clean source of energy, if it can be harnessed effectively.

In terms of safety and waste, nuclear fission produces radioactive waste that needs to be managed carefully, while nuclear fusion produces less radioactive waste. However, the high-energy neutrons produced by fusion can make the surrounding materials radioactive.