Radioactive half-life

The radioactive half-life , or period , is the time necessary so that half of the atoms of a radioactive Isotope disintegrates naturally.

It is sometimes called physical period to distinguish it from the biological half-life , which is time with the end of which half of an unspecified quantity of a radioactive isotope was eliminated from the organization.

The term Demi-vie is sometimes used as synonym of radioactive half-life.

Only one radioactive isotope

It is a property Statistique: lasted at the conclusion which the core of a radioactive Atome would have a chance on two to disintegrate. This property on an atomic nucleus scale does not depend on the environmental conditions, such as temperature, pressure, fields, but only of the Isotope considered. However, of recent work seem to show that one can largely modify this radioactive half-life to a significant degree. The first calculations of these authors show that one can make spend this period in the Ra 1600 years, in 16 month. That would make it possible to bring a solution to the problem of storage of the radioactive elements.

The number of atoms of a radioactive isotope which disintegrate naturally for a certain length of time does not depend as well as initial number of atoms. Consequently, the decrease of this number of atoms follows a decreasing exponential function.

The natural disintegration of the atoms of a given isotope can include/understand several modes of disintegration; in this case, the proportion of each one as of these modes is usually indicated expressed as a percentage. For example, the Chlorine 36, of period 301.000 years, comprises two modes of disintegration:

  • Disintegration béta in 36Ar, with emission of a radiation béta of 0,709 MeV (98% of disintegrations)
  • Orbital electron capture with transmutation into 36S, emission of a Gamma ray of 1,142  MeV (2% of disintegrations).
The period can vary considerably from one isotope to another, since a fraction of a second to million or billion years.

The Activité of a given number of atoms of a radioactive isotope is proportional to this number and inversely proportional to the radioactive half-life of the isotope.

References

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