Activity

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”).

Well-type ionization chamber
Measuring device for coincidence measurements

Verification and metrological control of activity measuring instruments

Activity measuring instruments are subject to mandatory verification in Austria. Activity measuring instruments which are based on the gamma-spectroscopic measuring principle are subject to metrological control by the BEV. Acceptable for verification are only activity measuring instruments which have been type approved by the BEV. The approval for metrological control of activity measuring instruments based on the gamma-spectroscopic measuring principle is granted by the BEV.

The verification of activity measuring instruments is carried out by the BEV. The interval for subsequent verification for activity measuring instruments is 2 years. The metrological control has to be carried out each year.

Activity measuring instruments, which are used in the sense of the radiation protection act for the physical control of the inner exposition to radiation (internal dose monitoring) of radiation exposed workers, may only be operated by approved dosimetric services and are subject to metrological control by the BEV. The approval of dosimetric services for the internal dose monitoring is granted by the BEV, an accreditation with respect to the requirements of the Metrology Act is equivalent to the approval by the BEV. The metrological control of activity measuring instruments used by approved dosimetric services has to be carried out annually.