Nuclear fuel refers to any fuel that is consumed or used as the driving force for nuclear energy, most often generated through a fission process where the fuel’s atomic elements are forcibly divided in order to produce energy. This fuel typically has to have highly fissionable elements that can absorb neutrons that bombard them in order to be easily split and allow for the harnessing the energy that is produced. Nuclear fuel can also either refer directly to the material that is directly used for the nuclear fission process or the physical objects that are developed from the base fuel and are compositions of both the base material and other elements (such as fuel rods that are a mixture of the raw fissionable fuel and either either structural, neutron moderating or neutron reflecting materials that can aid in the process of fission). The most common base fuels that is used in nuclear reactors are either uranium 235 or plutonium 239, Both of which form the backbones of nuclear power generation in modern years.
Other derivatives of nuclear fuel are used in less common, more contained power generation ways that may not produce as ample amount of energy as the fission process however are generally more contained and safer. This includes the isotope plutonium 238 and other elements that can be used to produce nuclear power through a simple matter of radioactive decay and are very common in atomic batteries and other long-term regular output energy sources. There are a number of other fuel elements that are are also used in alternative forms of nuclear power (such as tritium) and can be found as catalysts in the fusion rather than fission process of nuclear power generation where rather than by splitting atoms for energy molecules are forcibly joined together in order to generate power. This process is most common today in hydrogen fuel cells where hydrogen and oxygen are fused to create the byproduct of water while generating electricity.
In order to be effectively used as nuclear power on an ongoing basis all nuclear fuels undergo what is referred to as the nuclear fuel cycle, also commonly known as the nuclear fuel chain. This is a progression of steps that either generate a “closed cycle” in which nuclear fuel that has been expended in one round can be reprocessed and reintroduced into a system that will allow it to continue being used in other ways or an “open cycle” in which use nuclear fuel is treated, packaged and disposed of properly once it has been initially expended. While an open fuel cycle was more common in the past as nuclear fuel was generally unable to be reprocessed and reused effectively after its initial expenditure there are a number of modern-day nuclear reactors that allow the for the more efficient and effective neutron bombardment of nuclear fuel and related materials (such as fuel rods that are common in virtually all nuclear power plants in order to increase energy productivity) in order to more efficiently utilize the fissionable material found within the previously expended fuel sources. This allows modern-day nuclear reactors have a much higher efficiency rate in processing fuel (up to 60 times as effective as older model nuclear reactors) and allows for a regular closed cycle that is much more beneficial to the environment. This diagram illustrates the nuclear fuel cycle in greater detail for both closed and open nuclear processing.