Strontium unit Strontium unit The strontium unit is a unit used to measure the amount of radioactivity from strontium-90, a radionuclide found in nuclear fallout, in a subject's body. Since the human body absorbs strontium as if it were calcium, incorporating it into the skeleton, its presence is very common. One strontium unit is equal to one picocurie from strontium-90 per gram of calcium (37 becquerels per kilogram) in the subject's skeleton. The United States National Academy of Sciences holds that the maximum safe measure of strontium-90 in a person is one hundred strontium units (3700 Bq/kg). The average American is estimated
Specific activity the radionuclide is given by where "m" is mass number of the radionuclide and "N" is the Avogadro constant. Specific radioactivity "a" is defined as radioactivity per unit mass of the radionuclide: In addition, decay constant "λ" is related to the half-life "T" by the following equation: Thus, specific radioactivity can also be described by This equation is simplified by When the unit of half-life converts a year For example, specific radioactivity of radium-226 with a half-life of 1600 years is obtained by This value derived from radium 226 was defined as unit of radioactivity known as Curie (Ci). Experimentally