Decay Rate/Half-Life of Radioisotopes - Illustrations
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  • Radioactive half-life is the time required for a quantity of a radioisotope to decay by half.
  • If the half-life of an isotope is relatively short, e.g. a few hours, most of the radioactivity will be gone in a few days.
  • If the half-life of an isotope is relatively long, e.g. 80 years, it will take a long time for significant decay to occur.

Decay Rate/Half-Life of Radioisotopes

Adapted from Radiological Dispersal Device (RDD) (PDF - 2.34 MB) (Argonne National Laboratory)

Graph showing number of half lives against percent of initial activity remaining

Adapted from Radiation Terminology (PDF - 290 KB) (US NRC Technical Training Center)