Electron-capture effects in activity determination of 192Ir by a 4π β-γ coincidence counting method

Abstract

The radioactivity of 192Ir was measured by using a 4π β-γ coincidence counting system with a pressurized 4π proportional counter and two NaL(Tl) scintillation detectors. An efficiency-extrapolation method using low-energy threshold-level variation was applied to determine the activity of 192Ir. In order to investigate the influences of the electron-capture decay of 192Ir on the activity measurement, the measurement was carried out using four different gamma gates. The influences of the decay process were evaluated from the decay-scheme parameters and the count rates obtained from these gates and then used to make the necessary corrections in order to determine the activity. The final results obtained from each gamma gate showed good agreement within one standard deviation.