Guidance on Selection of Radiation Type

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Various Radiation Types Differ in Biological Effectiveness

An example is 125I, which emits four different radiation types used by IREP: photons < 30 keV, photons at 30-250 keV, electrons < 15 keV, and electrons > 15 keV (refs. [1] and [2]). Each of these radiation types contributes significantly to the dose to the thyroid, and each has a different biological effectiveness. Other examples include 58Co and 65Zn, both of which emit low-energy electrons (< 15 keV), higher-energy positrons (positively-charged electrons) from beta decay, low-energy photons (< 30 keV), and high-energy photons (> 250 keV), all with significant intensities.

References:

  1. International Commission on Radiological Protection (ICRP), Radionuclide Transformations: Energy and Intensity of Emissions, ICRP Publication 38, Ann. ICRP 11-13, Pergamon Press, Oxford, U.K. (1983).
  2. D. C. Kocher, Radioactive Decay Data Tables, DOE/TIC-11026, U.S. Department of Energy, Oak Ridge, Tennessee (available through National Technical Information Service, Springfield, Virginia) (1981).