Nuclear Fission | Universe Today

Written by John Carl Villanueva

Nuclear fission is the term used to refer to the splitting of an atom's nucleus into smaller fragments. Some of these fragments can be neutrons, photons and other nuclei. When heavy nuclei (they're the nuclei of elements found at the lower portion of your periodic table) undergo fission, large amounts of energy can be released.

It is for this reason why nuclear fission lies at the heart of the technology that drives nuclear power plants and nuclear weapons. As of 2007, 14% of electricity produced globally came from nuclear power plants, practically all of which were driven by nuclear fission.

The high energies released come in two main forms: electromagnetic waves like gamma rays and kinetic energy of the fragments. Due to their high energies, gamma rays are capable of ionizing atoms that cross their path. If the atoms are found in cells, the cells can undergo mutation. Aha! So now you know where the idea of the Incredible Hulk originated.

Despite the risks commonly associated with nuclear power, the amount of usable energy produced by such energy sources – which are millions of times greater than conventional sources of energy (gasoline, for example) – still make it an attractive option for some countries. Australia, Brazil, Canada, China, France, Iran, Japan, and the United States are some of the countries that have nuclear reactors.

Nuclear reactions in devices built to foster them are initiated by the bombardment of subatomic particles (neutrons, for instance) on fissile atomic nuclei (we'll define 'fissile' in a short while). These processes eventually lead to the splitting of the atomic nuclei. The free neutrons released after the bombarded nuclei undergo nuclear fission end up inducing more nuclear (fission) reactions.

A sequence of nuclear reactions, known as a chain reaction, then ensues. In some instances, fission chain reactions can be sustained. The types of nuclei, or isotopes, that are capable of sustaining them are good nuclear fuels. 'Fissile' is the term used to describe isotopes with such characteristics. Uranium-235 and Plutonium-239 are two of the most commonly used nuclear fuels.

Fission can also occur spontaneously in very massive isotopes. The products of this radioactive decay process, aptly known as spontaneous fission, are the same as those of the induced kind mentioned earlier. It is the process by which the products are obtained that differs. Here, no bombardment is needed for this type of nuclear fission to occur.

We've written several articles about nuclear fission for Universe Today. Here's an article about a mini nuclear reactor that could be used on the Moon.

Filed under: Astronomy

Tags: Gamma rays, nuclear fission, nuclear reaction