Nuclear fusion From Wikipedia, the free encyclopedia Jump to: navigation, search Nuclear physics Radioactive decay Nuclear fission Nuclear fusion Classical decays[show] Alpha decay · Beta decay · Gamma radiation Advanced decays[show] Double beta decay · Double electron capture · Internal conversion · Isomeric transition · Cluster decay · Spontaneous fission Emission processes[show] Neutron emission · Positron emission · Proton emission Capturing[show] Electron capture · Neutron capture R · S · P · Rp High energy processes[show] Spallation · Cosmic ray spallation · Photodisintegration Nucleosynthesis[show] Stellar Nucleosynthesis Big Bang nucleosynthesis Supernova nucleosynthesis Scientists[show] Becquerel · Bethe · Curie · Fermi · Rutherford · Bhabha · Ahmad v · d · e Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy. Fusion is the process that powers active stars, the hydrogen bomb and experimental devices examining fusion power for electrical generation. The fusion of two nuclei with lower masses than iron (which, along with nickel, has the largest binding energy per nucleon) generally releases energy, while the fusion of nuclei heavier than iron absorbs energy. The opposite is true for the reverse process, nuclear fission. This means that fusion generally occurs for lighter elements only, and likewise, that fission normally occurs only for heavier elements. There are extreme astrophysical events that can lead to short periods of fusion with heavier nuclei. This is the process that gives rise to nucleosynthesis, the creation of the heavy elements during events like supernovas. Creating the required conditions for fusion on Earth is very difficult, to the point that it has not been accomplished at any scale for protium, the common light isotope of hydrogen that undergoes natural fusion in stars. In nuclear weapons, some of the energy released by an atomic bomb is used to compress and heat a fusion fuel containing heavier isotopes of hydrogen, and also sometimes lithium, to the point of "ignition". At this point, the energy released in the fusion reactions is enough to briefly maintain the reaction. Fusion-based nuclear power experiments attempt to create similar conditions using less dramatic means, although to date these experiments have failed to maintain conditions needed for ignition long enough for fusion to be a viable commercial power source. Building upon the nuclear transmutation experiments by Ernest Rutherford, carried out several years earlier, the laboratory fusion of heavy hydrogen isotopes was first accomplished by Mark Oliphant in 1932. During the remainder of that decade the steps of the main cycle of nuclear fusion in stars were worked out by Hans Bethe. Research into fusion for military purposes began in the early 1940s as part of the Manhattan Project, but this was not accomplished until 1951 (see the Greenhouse Item nuclear test), and nuclear fusion on a large scale in an explosion was first carried out on November 1, 1952, in the Ivy Mike hydrogen bomb test. Research into developing controlled thermonuclear fusion for civil purposes also began in earnest in the 1950s, and it continues to this day. Two projects, the National Ignition Facility and ITER are in the process of reaching breakeven after 60 years of design improvements developed from previous experiments.

Nuclear fusion

From Wikipedia, the free encyclopedia

Jump to: navigation, search

Nuclear physics
Radioactive decay Nuclear fission Nuclear fusion
Classical decays[show] Alpha decay · Beta decay · Gamma radiation
Advanced decays[show] Double beta decay · Double electron capture · Internal conversion · Isomeric transition · Cluster decay · Spontaneous fission
Emission processes[show] Neutron emission · Positron emission · Proton emission
Capturing[show] Electron capture · Neutron capture R · S · P · Rp
High energy processes[show] Spallation · Cosmic ray spallation · Photodisintegration
Nucleosynthesis[show] Stellar Nucleosynthesis Big Bang nucleosynthesis Supernova nucleosynthesis
Scientists[show] Becquerel · Bethe · Curie · Fermi · Rutherford · Bhabha · Ahmad
v · d · e

Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy. Fusion is the process that powers active stars, the hydrogen bomb and experimental devices examining fusion power for electrical generation.
The fusion of two nuclei with lower masses than iron (which, along with nickel, has the largest binding energy per nucleon) generally releases energy, while the fusion of nuclei heavier than iron absorbs energy. The opposite is true for the reverse process, nuclear fission. This means that fusion generally occurs for lighter elements only, and likewise, that fission normally occurs only for heavier elements. There are extreme astrophysical events that can lead to short periods of fusion with heavier nuclei. This is the process that gives rise to nucleosynthesis, the creation of the heavy elements during events like supernovas.
Creating the required conditions for fusion on Earth is very difficult, to the point that it has not been accomplished at any scale for protium, the common light isotope of hydrogen that undergoes natural fusion in stars. In nuclear weapons, some of the energy released by an atomic bomb is used to compress and heat a fusion fuel containing heavier isotopes of hydrogen, and also sometimes lithium, to the point of "ignition". At this point, the energy released in the fusion reactions is enough to briefly maintain the reaction. Fusion-based nuclear power experiments attempt to create similar conditions using less dramatic means, although to date these experiments have failed to maintain conditions needed for ignition long enough for fusion to be a viable commercial power source.
Building upon the nuclear transmutation experiments by Ernest Rutherford, carried out several years earlier, the laboratory fusion of heavy hydrogen isotopes was first accomplished by Mark Oliphant in 1932. During the remainder of that decade the steps of the main cycle of nuclear fusion in stars were worked out by Hans Bethe. Research into fusion for military purposes began in the early 1940s as part of the Manhattan Project, but this was not accomplished until 1951 (see the Greenhouse Item nuclear test), and nuclear fusion on a large scale in an explosion was first carried out on November 1, 1952, in the Ivy Mike hydrogen bomb test.
Research into developing controlled thermonuclear fusion for civil purposes also began in earnest in the 1950s, and it continues to this day. Two projects, the National Ignition Facility and ITER are in the process of reaching breakeven after 60 years of design improvements developed from previous experiments.