Fission
Summary
When a heavy nucleus (Uranium, for example) fissions, it splits into two smaller nuclei. Two or three neutrons are also emitted.
The sum of the masses of these fragments is less than the original mass. This 'missing' mass has been converted into a large amount of energy according to Einstein's equation E = mc². When the fissionable material is confined, the emitted neutrons bombard and split other nuclei, provoking a chain reaction, either controlled (as in a nuclear reactor) or uncontrolled (as in an atomic bomb).
Don't confuse fission with fusion.
Learning objectives
- To illustrate the fission process and what a chain reaction is.
Learn more
Nuclear fission is the splitting of a heavy atomic nucleus (uranium for example) into two or more lighter nuclei. This reaction results in the release of 2 or 3 neutrons and great amounts of energy. In a confined medium, the extra neutrons collide with other nuclei to cause a chain reaction which can be used in atomic weapons and in nuclear power plants.
Further Information:
Fission can occur naturally, as it does in granitic rock, or be induced in a confined medium. Only those elements with an atomic number above 88 are fissile. In accordance with Einstein’s formula expressing the equivalence between mass and energy, the sum of the atomic weights produced is less than the atomic weight of the initial element, the difference being released in the form of fission energy. By colliding with other particles, this nuclear energy is transformed into heat which can be used to produce electricity. The half-life is the period required for the initial quantity of an element to decrease by half. For example, uranium 235 can be broken down into several elements including xenon 134 and strontium 90 and has a half-life of over 700 million years.
