Nuclear physics
Nuclear Fission
The splitting of heavy atomic nuclei (typically uranium-235 or plutonium-239) into lighter fragments, releasing large amounts of energy.
Fission is the energy-release mechanism in atomic bombs and most nuclear power plants. Each fission event releases roughly 200 MeV of energy and 2–3 neutrons, which can sustain a chain reaction if a critical mass of fissile material is assembled.
Related terms
Nuclear Fusion
The combination of light atomic nuclei (typically deuterium and tritium) into heavier nuclei, releasing energy.
Critical Mass
The minimum amount of fissile material required to sustain a self-propagating nuclear chain reaction.
Uranium-235
A fissile isotope of uranium that constitutes the explosive material in many fission weapons.
Plutonium-239
A fissile isotope of plutonium produced from uranium-238 in nuclear reactors and used in most modern fission weapons.