By Zain Waheed - Engineering Student @ St John's College, Cambridge
Ever since nuclear fusion was discovered in 1930, by the experiments of Fritz Houtermans and Robert Atkinson, engineers and physicists have been attempting to harness and implement the immense amount of energy released by fusion, but in an efficient and practical manner.
Fusion and Fission reactions are examples of nuclear processes in which energy is released due to changes in atomic nuclei. Nuclear fission occurs when a large, unstable isotope is bombarded with high-speed, and hence high-energy, neutrons. This collision of the accelerated neutrons with the nucleus of the atom result in the atom splitting up into 2 (or more) much more stable, smaller isotopes and releasing a large amount of energy in a chain reaction. Fission reactions are relatively simple to manage and moderate due to the minuscule amount of energy required in the actual splitting of the atom. The main isotope used in fission reactions is Uranium-235.
On the other hand, nuclear fusion occurs when two low-mass isotopes - typically isotopes of hydrogen - unite under conditions of extreme pressure and temperature. Like fission, this process also produced an enormous amount of energy. The atoms used most frequently in fusion reactions are those of tritium and deuterium. Nuclear fusion produces up to 4 times the energy produced in fission and also produces fewer harmful by-products. Yet, nuclear fission is still much more commonly used in nuclear power plants. This is due to the extreme temperatures and pressures which are required to enable these reactions to take place. Fusion reactions require about 100 million Kelvin of temperature which is approximately 6 times hotter than the Sun’s core. At these temperatures, hydrogen is a plasma, not a gas, which makes it much more difficult to control.
One major theory that makes fusion reactions feasible by overcoming the issues of extreme temperatures is that of “cold-fusion”. Cold fusion is a hypothetical process in which hydrogen fusion supposedly occurs at room temperature. The topic is controversial, because the notion appears to defy the laws of physics. Some scientists believe that cold fusion represents a real phenomenon and that it will someday form the basis for an abundant, cheap source of energy. Others maintain that cold fusion, like perpetual motion, is impossible. In 1989, Stanley Pons and Martin Fleischmann of the University of Utah claimed to have produced hydrogen fusion in a controlled experiment at room temperature. But these results have proven difficult to reproduce. This has meant that the idea of cold-fusion has not been fully accepted in the scientific community but, nevertheless, it has the potential of making fusion possible.
Aside from the concept of cold-fusion, there are alternate ways in which nuclear fusion could advance. A company based in the UK, called “Tokamak Energy”, which specialises in nuclear fusion technologies have proposed many practical ideas to overcome the issue of extreme heat. They achieved this once in the production of a small-scale nuclear reactor called the ST40. To reach these high temperatures, the ST40 uses a process known as merging compression. This releases energy as rings of plasma, which collide and produce magnetic fields that “snap” together, in a process known as magnetic reconnection. This shows the potential of nuclear fusion and reminds us that it is more than possible to implement it in the near future.
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