Improvement of software coincidence counting system for standardisation of EC-β(+) radionuclides

Since 2000 the software coincidence counting (SCC) system has been used for activity standardisation of about 15 radionuclides. Their activities were determined by the efficiency extrapolation method applied to 4π (PC)-γ coincidence. Some standardisations, mainly standardisations of EC-β(+) radionuclides, required optimal setting of coincidence parameters, for which new procedures based on "the coincidence to total PC count ratios", "a multiple gamma window combined from subwindows fractions" and "a source test for PC detection efficiency " were introduced. The paper summarises the development of SCC system related to findings from detailed analyses of recorded data. These findings are not practically achievable by a conventional approach.