Standardization of 241Am, 124Sb and 131I by live-timed anti-coincidence counting with extending dead time

The National Metrology Laboratory for Ionizing Radiation (LNMRI)/Brazil has implemented a live-timed anti-coincidence system with extending dead time to complement the existing systems in its Radionuclide Laboratory for activity measurements of radioactive sources. In this new system, the proportional counter has been replaced by a liquid-scintillation-counter for alpha and beta detection. In order to test the performance of the new system, radioactive solutions of 131I, 124Sb and 241Am have been standardized. In this work the measurement method, the results and the associated uncertainties are described and discussed.