The Collaborative International Dictionary
nuclear reaction \nuclear reaction\ n. A process that alters the energy or structure or composition of an atomic nucleus.
Wiktionary
n. a process such as the fission of an atomic nucleus, or the fusion of one or more atomic nuclei and / or subatomic particles in which the number of protons and / or neutrons in a nucleus changes; the reaction products may contain a different element or a different isotope of the same element
WordNet
n. (physics) a process that alters the energy or structure or composition of atomic nuclei
Wikipedia
In nuclear physics and nuclear chemistry, a nuclear reaction is semantically considered to be the process in which two nuclei, or else a nucleus of an atom and a subatomic particle (such as a proton, neutron, or high energy electron) from outside the atom, collide to produce one or more nuclides that are different from the nuclide(s) that began the process. Thus, a nuclear reaction must cause a transformation of at least one nuclide to another. If a nucleus interacts with another nucleus or particle and they then separate without changing the nature of any nuclide, the process is simply referred to as a type of nuclear scattering, rather than a nuclear reaction.
In principle, a reaction can involve more than two particles colliding, but because the probability of three or more nuclei to meet at the same time at the same place is much less than for two nuclei, such an event is exceptionally rare (see triple alpha process for an example very close to a three-body nuclear reaction). "Nuclear reaction" is a term implying an induced change in a nuclide, and thus it does not apply to any type of radioactive decay (which by definition is a spontaneous process).
Natural nuclear reactions occur in the interaction between cosmic rays and matter, and nuclear reactions can be employed artificially to obtain nuclear energy, at an adjustable rate, on demand. Perhaps the most notable nuclear reactions are the nuclear chain reactions in fissionable materials that produce induced nuclear fission, and the various nuclear fusion reactions of light elements that power the energy production of the Sun and stars. Both of these types of reactions are employed in nuclear weapons.
Usage examples of "nuclear reaction".
As a source of power, yes, sometime in the distant future when there had been more opportunity to deal with the extremely ticklish problem of controlling the nuclear reaction.
With no reactor coolant to absorb the heat of the uranium rods, the nuclear reaction actually stopped —.
With no reactor coolant to absorb the heat of the uranium rods, the nuclear reaction actually stopped—.
We'll control the nuclear reaction with cadmium rods that capture excess neutrons before they strike uranium atoms.
It uses a controlled nuclear reaction to,create the electron-particle stream necessary for lasing.
There remains a third type of nuclear reaction to be taken into consideration.
In the last two years, the first of the nuclear reaction mass engines had hit the roads.