Fusion has the potential to provide practically inexhaustible energy with greatly reduced levels of radioactive waste compared with fission.
International Fusion Research: "The nuclear reactions that release energy by combining light nuclei, like hydrogen, to form heavier nuclei, such as helium, are called fusion. They are, in a sense, the opposite of the nuclear fission reactions that power present-day nuclear plants; fission breaks up the nuclei of heavy elements such as uranium. Fusion has the potential to provide practically inexhaustible energy with greatly reduced levels of radioactive waste compared with fission.
To make fusion reactions take place requires the fuel to be heated to tremendously high temperatures (over 100 million degrees), so that it enters an electrically-conducting state beyond that of a gas. This state of matter is called plasma. The plasma must also be maintained long enough for the reactions to occur.
Fusion is the energy source that powers the sun and stars. In these natural fusion reactors, it is gravity that confines the plasma in a wonderfully stable and long-lived configuration. A human-scale fusion reactor must also use a non-material container, but to make the reactor small enough, it must use a much stronger force than gravity: the force of a magnetic field. ITER is to be a magnetic confinement device of the type called a tokamak, which has a toroidal (donut-shaped) configuration and a strong, confining magnetic field. The tokamak configuration has been under study by fusion plasma scientists since the 1960s, and has proven to have the best confinement of all the configurations so far envisioned.
Even so, the achievement of sufficiently good confinement of the plasma to permit useful release of energy has turned out to be far more difficult than the first fusion researchers hoped. Many important optimizations have been discovered and developed. One unavoidable way to obtain sufficient confinement is to make the plasma large. The existing large tokamak experiments typically have plasma radii of three meters. Fueled with the most reactive isotopes of hydrogen, those tokamaks demonstrated substantial release of fusion energy. For example, the world's largest tokamak, JET (Joint European Torus), obtained up to 16 megawatts of fusion reactions for just under a second. But, to sustain the plasma in these devices required additional heating that was larger.
The next big step in fusion development is to create a plasma that keeps itself hot by the energy released in its own fusion reactions. The ITER international collaboration has developed a design to sustain such a so-called "burning plasma," generating about 500 megawatts of fusion reactions for approximately 1,000 seconds. To achieve this requires a plasma about twice as large, and also requires the use of superconducting magnets that consume negligible electric power for their operation."
To make fusion reactions take place requires the fuel to be heated to tremendously high temperatures (over 100 million degrees), so that it enters an electrically-conducting state beyond that of a gas. This state of matter is called plasma. The plasma must also be maintained long enough for the reactions to occur.
Fusion is the energy source that powers the sun and stars. In these natural fusion reactors, it is gravity that confines the plasma in a wonderfully stable and long-lived configuration. A human-scale fusion reactor must also use a non-material container, but to make the reactor small enough, it must use a much stronger force than gravity: the force of a magnetic field. ITER is to be a magnetic confinement device of the type called a tokamak, which has a toroidal (donut-shaped) configuration and a strong, confining magnetic field. The tokamak configuration has been under study by fusion plasma scientists since the 1960s, and has proven to have the best confinement of all the configurations so far envisioned.
Even so, the achievement of sufficiently good confinement of the plasma to permit useful release of energy has turned out to be far more difficult than the first fusion researchers hoped. Many important optimizations have been discovered and developed. One unavoidable way to obtain sufficient confinement is to make the plasma large. The existing large tokamak experiments typically have plasma radii of three meters. Fueled with the most reactive isotopes of hydrogen, those tokamaks demonstrated substantial release of fusion energy. For example, the world's largest tokamak, JET (Joint European Torus), obtained up to 16 megawatts of fusion reactions for just under a second. But, to sustain the plasma in these devices required additional heating that was larger.
The next big step in fusion development is to create a plasma that keeps itself hot by the energy released in its own fusion reactions. The ITER international collaboration has developed a design to sustain such a so-called "burning plasma," generating about 500 megawatts of fusion reactions for approximately 1,000 seconds. To achieve this requires a plasma about twice as large, and also requires the use of superconducting magnets that consume negligible electric power for their operation."
posted by Greta Jane at Saturday, July 09, 2005
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