Activity of a Material Containing One Natural Radionuclide

The activity of a mass of material m containing a mass fraction of a naturally occurring radionuclide of half-life and isotopic abundance is given by the following equation  

Tyj half-life of the radionuclide X in s Nj Avogadro s constant 6.02204532 x 10 mol dimensionless atomic isotopic abundance dimensionless mass fraction of the radionuclide in the material m mass of material in kg 

Therefore, the activity per unit mass of material, called the specific activity, denoted a, and expressed in Bq.kg , is given by the following equation  

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