secular equilibrium

secular equilibrium (plural secular equilibria or secular equilibriums)

1. (nuclear physics) The situation of the quantity of a radioisotope remaining constant because it is produced (by decay of a parent isotope) at the same rate that it decays.

   Synonym: radioactive equilibrium

   • 1998, Michael F. L'Annunziata, Handbook of Radioactivity Analysis, Academic Press, page 61:

     In decay schemes of this type, the following three conditions may predominate: (1) secular equilibrium, (2) transient equilibrium, and (3) the state of no equilibrium.

   • 2016, Tobias L. Ross, Frank Roesch, “Life sciences: Nuclear medicine diagnosis”, in Frank Rösch, editor, Nuclear- and Radiochemistry, Volume 2: Modern Applications, Walter de Gruyter, page 443:

     The ${\displaystyle {\ce {^{68}Ge/^{68}Ga}}}$ and the ${\displaystyle {\ce {^{82}Sr/^{82}Rb}}}$ generators represent secular equilibria.

   • 2020, David J. Burdige, Geochemistry of Marine Sediments, Princeton University Press, page 43:

     At the same time, because of differences in the chemistry of the daughter and parent elements involved in such secular equilibria, this parent:daughter ratio may not be equal to 1.

• Bateman equation on Wikipedia.Wikipedia
• Transient equilibrium on Wikipedia.Wikipedia