FIGURE D.1 Mass distributions resulting from fission of uranium-235 by thermal neutrons. SOURCE: Data from Joint Evaluated Fission and Fusion File, Incident-neutron data,, October 2, 2006; see

  • Alkali metals, for example, cesium-137.
  • Alkaline earth metals, for example, strontium-90.
  • Less commonly, hydrogen-3, more commonly referred to as tritium (T), from ternary fission of uranium atoms.

Neutron capture can also induce radioactivity through the transmutation of one chemical element into another. The transmutation process results in the emission of nuclear particles (e.g., protons) and radiation from the nucleus. Some transmutation reactions and products of significance in power reactors include the following:

  • Production of nitrogen-16 through the capture of a neutron by the nucleus of an oxygen atom: oxygen-16 + neutron —> nitrogen-16 + proton (abbreviated as 16O(n, p)16N). Nitrogen-16 has a short (7-second) half-life and is primarily a hazard to workers at nuclear plants.
  • Production of carbon-14 through the capture of neutrons by the nuclei of nitrogen, oxygen, or carbon atoms: 14N(n, p)14C; 13C(n, y)14C; 17O(n, a)14C.

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