Realization of the unit of activity
The activity A of radioactive substance (“radionuclide”) is the quotient of the expected value for the number of spontaneous nuclear transformations and the time interval in which these transformations take place. The unit of measurement of activity is the Becquerel (Bq). (1 Bq = 1 / s)
The standard of the BEV for the realization of the unit of the activity is a well-type ionization chamber.
Area sources are the standards of the BEV for the realization of the unit Becquerel/square meter (Bq/m²), the activity of radioactive sources related to the area. The standard of the BEV for the realization of the unit Becquerel/cubic meter (Bq/m3), the concentration of the activity of ²²²Rn in air CA (²²²Rn) is an ionization chamber. All these standards are traceable to primary standards of other NMIs.
Additionally to these calibrations the BEV participates in comparison measurements with the Bureau International des Poids et Mesures (BIPM) in Paris within the framework of the international reference system for radionuclides (“SIR”).