Nuclear Fission
The process of splitting a heavy atomic nucleus (such as uranium-235 or plutonium-239) into two lighter nuclei, releasing a large amount of energy. This is the reaction that powers all current nuclear power plants.
Why It Matters
Fission provides about 19% of U.S. electricity — the largest single source of carbon-free power. Understanding fission vs. fusion clarifies what nuclear energy can and cannot do today.
Related Topics
Related Terms
Nuclear Fusion
The process of combining light atomic nuclei (typically hydrogen isotopes deuterium and tritium) to form heavier nuclei, releasing enormous energy. Fusion powers the sun but has not yet been achieved at commercial scale on Earth.
Uranium
A naturally occurring radioactive element used as fuel in nuclear reactors. Natural uranium is 99.3% U-238 and 0.7% U-235. Most reactors require enrichment to 3-5% U-235.
Chain Reaction
In nuclear fission, a self-sustaining series of reactions where neutrons released by splitting one atom cause additional atoms to split, releasing more neutrons and energy. Reactors control this process; bombs let it run away.