Physics

Difference between Nuclear Fusion and Nuclear Fission



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Both nuclear fission and nuclear fusion are both processes which, with the appropriate technology, can be used to produce large amounts of energy - either for power, or for destructive purposes. However, they are actually quite different chemical processes. Essentially, nuclear fission involves splitting atoms apart, while nuclear fusion involves pushing atoms together.

- Nuclear Fission -

Nuclear fission is the splitting of an atom into smaller constituent parts. All atoms are made up of a central nucleus of protons and neutrons, which is constantly orbited by electrons. When they split up, the nucleus flies apart into separate clumps of those protons and neutrons. Once this has happened, those clumps, on their own, are still atoms - but they are different atoms.

In chemical terms, the type of element (or chemical) that an atom will be is determined by the number of protons in its nucleus. When nuclear fission occurs, either only neutrons are lost from the atom (in which case it remains the same chemical), or, alternatively, the entire nucleus breaks up. In that case, the result is the creation of multiple new chemical elements. For example, when uranium undergoes nuclear fission, its atoms break up, or "decay," into radium.

Splitting up atoms takes a considerable amount of energy. However, when particularly heavy atoms (those below iron on the periodic table) break up, they release a much greater amount of energy - which is what makes nuclear fission attractive for power purposes. Because it is easiest and most efficient to break up extremely heavy atoms, all current nuclear fission applications use the atoms at the bottom of the periodic table: uranium, and sometimes plutonium.

The advantage of splitting up atoms is that as this occurs, part of the energy which used to go into holding the atom together is released. Today this energy is harnessed in nuclear power plants, and used by the military in nuclear weapons. The process of the atom disintegrating also leads to a variety of particles firing out of the atom at high velocity - what we know of, more commonly, as radiation or radioactivity. For this reason, both nuclear power plants and the decayed former fuel supplies that are removed from them are radioactive and highly dangerous. The two most important safety issues with relation to nuclear power plants are preventing dangerous explosions or meltdowns in an operating reactor, as occurred in Chernobyl in 1986; and in finding safe underground storage spaces where the spent fuel will not pose health risks.

- Nuclear Fusion -

Nuclear fusion is a similar atomic process, but works in reverse: this is the process by which atoms are pushed together, forming new, larger atoms. This is a common process in nature: all stars, including our own Sun, are hot and bright because of the energy given off by fusion reactions going on in their cores.

As was the case with nuclear fission, the type of element that emerges from fusion is determined by the number of protons in its nucleus. When nuclear fusion occurs, two atomic nuclei are fused together. In the case of the Sun, for instance, the fusion process involves forcing two hydrogen atoms together, each of which has one proton in its nucleus. This creates a new nucleus with two protons in it - a chemical we call helium.

It takes extremely large amounts of energy to create the heat and pressure necessary to begin pushing atoms together - far more so than it does to split them apart. However, once light atoms (those at the top of the periodic table) actually begin to fuse, they release a far greater amount of energy. For this reason, many scientists believe that the future of nuclear power lies with fusion rather than fission. Hydrogen is the lightest atom, and therefore the easiest to fuse, forming helium.

The difficulty, however, is in finding a way to create the heat and power efficiently. Today's thermonuclear bombs, also known as hydrogen bombs, do undergo nuclear fusion - but in order to get enough energy for fusion to occur, they actually have to set off an internal fission-based nuclear bomb first. Current technology does not actually allow us to build a nuclear fusion power plant. If nuclear fusion could be harnessed safely, however, there are a number of clear advantages. Nuclear fusion releases more energy than nuclear fission, and does so without releasing potentially hazardous radiation (because particles are being forced together rather than blown apart).

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