In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into two or more smaller, lighter nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay.
This process is used to create electricity in nuclear power stations.
A natural nuclear fission reactor is a uranium deposit where self-sustaining nuclear chain reactions have occurred. The phenomenon was discovered in 1972 in Oklo, Gabon, and this is still the only known location for this in the world. It consists of 16 sites with patches of centimeter-sized ore layers. Here self-sustaining nuclear fission reactions are thought to have taken place approximately 1.7 billion years ago, and ran for a few hundred thousand years, averaging probably less than 100 kW of thermal power during that time.
Only 4 kilograms of uranium are required to power nuclear submarines for 30 years without refueling. The reactors used in nuclear submarines are based on highly enriched uranium (HEU), which contains 90% or more uranium-235. 4 kilograms of enriched uranium can power a nuclear submarine for several decades, as nuclear fission reactions produce a tremendous amount of energy. The energy produced by the fission of one kilogram of uranium-235 is equivalent to approximately 24,000,000 kilowatt-hours. The efficient use of fuel in nuclear reactors and the design of the reactor itself eliminate the need for frequent fuel replacements. Nuclear submarines do not require fuel replacements for 20-30 years, which is a significant technological advantage for their long-term missions. This is why nuclear submarines have greater autonomy than conventional diesel-electric submarines.
See also[]
Nuclear fusion which releases a vast amount more energy.