Early models of the atom considered only two types of particles; protons and electrons. We now need to realise that there is a third particle in the nucleus as this particle turns out to be the key to using nuclear processes for electricity generation.
Although natural radioactive decay happens spontaneously, it does not transfer energy at a fast enough rate to be used for generating electricity. In order to get a faster rate of energy transfer, something is required to drive a different process – and that “something” is a neutron.
For our purposes, a neutron can be thought of as a proton combined with an electron. Since protons and electrons have exactly equal but opposite charges, it follows that neutrons are neutral (they have no overall charge).
In addition, since an electron has just a tiny mass compared with a proton, it also follows that a neutron will have just very slightly more mass than a proton. That said, the exam board expects you to give a mass of “one” (1 atomic mass unit) to both protons and neutrons.
Some nuclei are less stable than others and these nuclei will break “in half” if they can be made to absorb an extra neutron. These semi-stable nuclei are said to be fissile (or fissionable) and the process of splitting is known as nuclear fission.
Nuclear fission is different from natural radioactive decay because it produces two different nuclei, rather than just one in natural decay. Another difference is that nuclear fission also releases more neutrons that can go on to cause other nuclei to break up.
Nuclear fission is self-sustaining and forms the basis of all current nuclear electricity generation.
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