Nuclear chain reaction | physics | Britannica (original) (raw)
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major reference
In chain reaction Nuclear chain reactions are series of nuclear fissions (splitting of atomic nuclei), each initiated by a neutron produced in a preceding fission. For example, 21/2 neutrons on the average are released by the fission of each uranium-235 nucleus that absorbs a low-energy neutron. Provided that… Read More
meltdown
In meltdown The chain reaction that occurs in the reactor’s core must be carefully regulated by control rods, which absorb neutrons, and a moderator, which reduces their energy. If the core becomes too hot, it can melt, releasing large amounts of radiation. See also Three Mile Island accident… Read More
nuclear fission
In nuclear fission …repeat the sequence, causing a chain reaction in which a large number of nuclei undergo fission and an enormous amount of energy is released. If controlled in a nuclear reactor, such a chain reaction can provide power for society’s benefit. If uncontrolled, as in the case of the so-called atomic… Read More
In nuclear fission: Fission chain reactions and their control …to the possibility of a chain reaction if at least one of the fission neutrons induces fission in another fissile nucleus, which in turn fissions and emits neutrons to continue the chain. If more than one neutron is effective in inducing fission in other nuclei, the chain multiplies more rapidly.… Read More
In actinoid element: Nuclear properties of the actinoids Nuclear reactors and atomic bombs depend upon the chain reaction set up by this process: the resulting neutrons react further, inducing more fission reactions, which produce more neutrons, which lead to still more fission reactions, with the result that, without control, a great deal of… Read More
nuclear reactor operation
In nuclear reactor: Chain reaction and criticality The course of a chain reaction is determined by the probability that a neutron released in fission will cause a subsequent fission. If the neutron population in a reactor decreases over a given period of time, the rate of fission will… Read More
nuclear weapons
In nuclear weapon: Producing a controlled chain reaction The possibility that an atomic bomb might first be developed by Nazi Germany alarmed many scientists and was drawn to the attention of U.S. Pres. Franklin D. Roosevelt by Albert Einstein, then living in the United States. The president appointed an Advisory Committee… Read More
production of infrared radiation
In radiation: Infrared rays …dangerous in the course of nuclear chain reactions. In the course of a nuclear detonation, a brief but very intense emission of infrared occurs, together with visible and ultraviolet light emitted from the fireball (flash burns). Of the total energy of nuclear explosion, as much as one-third may be in… Read More
