Activity standardization of 123I by liquid scintillation counting

Abstract Primary activity standardization of the radionuclide iodine-123 using 4π(X,e)(LS)-γ coincidence counting is presented in this paper. The activity concentration of an aqueous solution was determined by the efficiency extrapolation technique using neutral density filters. The measurements were realized using a digitizer-based data acquisition system. The coincidence analysis of the collected list-mode data was performed offline using a custom-developed computer code. The results were used to participate in an international comparison under the auspices of the International Bureau of Weights and Measures (BIPM) via the International Reference System (SIR) as well as the Transfer Instrument of the International Reference System (SIRTI).