Analytical calculations on radioactivity measurements of 192Ir metallic sources with a calibrated ionization chamber

Abstract

The self-attenuation of photons was analytically calculated for an 192Ir metallic wire source and an aqueous standard source. The influence of the self-attenuation on the current of the calibrated ionization chamber was also evaluated. The self-attenuation did considerably affect the ionization current. It was concluded that the apparent radioactivity must be multiplied by a correction factor larger than unity (1.09±0.01 in the present case) to get the true radioactivity when the radioactivity of the 192Ir metallic wire source was measured with the ionization chamber calibrated with the aqueous standard source of 192Ir.