Nuclear fusion is a nuclear reaction that two or more atomic nuclei collide at a high speed and join to form a new type of atomic nucleus. Matter is not conserved in this process because some of the mass of the fusing nuclei is converted to photons which are released though a cycle. Fusion is the process that powers our Sun and the stars.
The fusion of two nuclei with lower masses than iron generally releases energy, while the fusion of nuclei heavier than iron absorbed energy. This is oppositely true for nuclear fission. When heavier elements fuse in the atmosphere the process gives rise to nucleosynthesis, the creation of heavy elements during events such as supernovae.
In order for fusion to occur, a substantial energy barrier of electrostatic forces must be overcome. At far distances, two nuclei will repel each other because of the repulsive electrostatic force between their positively charged protons. If the two nuclei’s can overcome to electrostatic repulsion and be brought close together fusion can occur.
For the energy to be produced from a fusion reaction to be useful it must meet the following criteria.
- Be exothermic
- Involve low Z nuclei
- Have two reactants
- Have two or more products
- Conserve both protons and neutrons