![]() Decades of overly enthusiastic predictions have led to a long-running joke that fusion is the energy source of the future-and always will be.ġ. Vastly more is understood about the physics of fusion energy than in Eddington’s day, yet commercial electricity generation from fusion still remains a goal rather than a reality. Obviously, these early predictions were more than a little off-base. It was not long before journalists and pulp fiction authors were predicting a time, surely not far away, when the world would be powered by simple fusion reactors requiring nothing more than abundant hydrogen from water. When British physicist Arthur Stanley Eddington first proposed in the 1920s that the sun and stars were powered by the fusion of hydrogen into helium, his idea sparked a rush of research and speculation into the possibility of bringing this energy source to earth. But significant recent advances in fusion science and technology could potentially put the first fusion power on the grid as soon as the 2040s. © Copyright '1995-'2004 PhysLink.The joke about fusion energy is that it’s 30 years away and always will be. Martin Archer, Physics Student, Imperial College, London, UKĪll rights reserved. However, you must remember that an enormous amount of energy is required in order for these reactions to occur at all - that is why fusion is not yet a practical source of energy. This is 0.7MeV for fission and 6.2MeV for fusion so it is obvious that fusion is the more effective nuclear reaction. However, the energy per unit mass is more relevant. So it is easy to see that fusion reactions give out more energy per reaction. Considering the mass of the four protons/hydrogen nuclei (4.029106u) and the mass of the Helium produced (4.002603u) we get a mass difference of 0.026503u or 24.69MeV. Finally two Helium-3s fuse forming a Helium nucleus and two hydron nuclei. ![]() Then the deuterium fuses with another hydrogen to form Helium-3 and a photon of energy. In a fusion reaction firstly two hydrogens fuse to form a deuterium (an isotope of hydrogen with nucleon no 2), a positron and an electron neutrino. Now looking at the graph the binding energy per nucleon for Uranium is about 7.6MeV and for Barium around 8.3 giving an increase in binding energy during fission of about 0.7MeV per nucleon, or a total of 164.5MeV in total. An example of fission is when a Uranium-235 atom is split by a neutron into a Barium-144 atom, a Krypton-89 atom and three neutrons. To answer this you need to look at the binding energy per nucleon graph as follows: Fusion releases the energy of the strong force (much stronger at short distances than the EM force) when the small pieces are captured and held into one nucleus.īill Baird, Ph.D., Postdoc, College of Charleston, SC ![]() The energy per event is greater (in these examples) in fission, but the energy per nucleon (fusion = about 7 MeV/nucleon, fission = about 1 Mev/nucleon) is much greater in fusion.įission releases the energy of the electromagnetic force when positively charged parts of the nucleus fly away from one another. The energy released when 4 Hydrogen nuclei (= protons) fuse (there are some decays involved as well) into a Helium nucleus is around 27 Million Electron Volts (MeV), or about 7 MeV per nucleon.įor fission of U or P, energies released are around 200 MeV or so. Fusion only produces more energy than it consumes in small nuclei (in stars, Hydrogen & its isotopes fusing into Helium). Why does the nuclear fusion reaction yield more energy than the nuclear fission reaction?įission only produces more energy than it consumes in large nuclei (common examples are Uranium & Plutonium, which have around 240 nucleons (nucleon = proton or neutron)).
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