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Overview
Nuclear fission occurs when a heavy atomic nucleus splits into smaller nuclei. The process can release energy because the final products may have greater binding energy per nucleon than the original nucleus. Fission is used in nuclear power and is also the basis of certain nuclear weapons.
Splitting Heavy Nuclei
Heavy nuclei such as uranium or plutonium can split after absorbing a neutron or through other nuclear processes.
Energy Release
Fission releases energy because some mass-energy of the initial system is converted into kinetic energy of fragments, radiation, and other forms.
Neutrons
Fission often releases additional neutrons, which can trigger more fission events if they are absorbed by other fissile nuclei.
Chain Reaction
A chain reaction occurs when neutrons from one fission event cause additional fission events. Controlled chain reactions are used in reactors.
Nuclear Reactors
A nuclear reactor controls fission using fuel, moderators, control rods, coolant, shielding, and engineered safety systems.
Waste and Safety
Fission products can be radioactive and require careful handling, shielding, cooling, and long-term management.
Weapons Context
Uncontrolled rapid fission chain reactions can release enormous energy explosively. This is distinct from controlled reactor operation.
Common Mistakes
A common mistake is confusing fission with fusion. Fission splits heavy nuclei, while fusion joins light nuclei.
Why This Matters in Physics
Fission connects nuclear structure, binding energy, mass-energy equivalence, power generation, radiation, engineering, and public policy.