Secular equilibrium

The term secular equilibrium or permanent balance comes from nuclear physics and describes a relationship between the activities of radionuclides within a decay chain or in the production of artificial radionuclides. Parent is called radioactive equilibrium.

For some radionuclides, the decay product ( " daughter nuclide " ) itself is again radioactively circumstances - this may include several generations - such as in the primordial isotopes of uranium and thorium.

If the half-life of the parent, is substantially longer than that of the daughter nuclide, then the activity of the daughter approximates the time the activity of the parent nuclide. If both activities are equal, the secular equilibrium is reached, as in this state, the parent nuclide supply those from the decay always just so many atoms of the daughter nuclide as decay in the same period Tochternuklidatome.

Transient equilibrium: The half-life of Mutternuklides is still well above that of the Tochternuklides (intersection at the maximum daughter activity)

Missing balance No equilibrium is reached more when the half-lives are in the same range ( the intersection again in the subsidiary maximum activity)

• Nuclear physics