Estimation of self-absorption correction coefficients for gross-alpha activity measurements

Abstract

Optimizing the sample volume is an important consideration while preparing planchets for measuring gross-alpha activity in environmental water samples. A higher sample volume results in increased thickness, which has a significant impact on gross-alpha activity measurements due to self-absorption in the samples. Moreover, while evaporating water samples on planchets to dryness, necessary precautions must be taken to prevent the loss of sample mass due to excessive heating. The present study represents a preliminary effort to estimate self-absorption correction coefficients and the efficiency of the detector, corrected for self-absorption, for estimating gross-alpha activity. The self-absorption correction coefficient versus sample volume is determined by performing gross alpha counting of different volumes of IAEA reference water samples. This is achieved through planchet preparations using varying quantities of water samples (ranging from 1 ml to 5 ml in steps of 1 ml, and from 10 ml to 20 ml in steps of 5 ml). The study also examines the effect of sample volume on the detector's efficiency for gross-alpha activity measurements. Additionally, the study highlights the impact of different drying methods in planchet preparations on gross-alpha activity measurements. The study reveals that the self-absorption correction coefficient decreases with increasing sample volume, indicating that larger sample volumes require more corrections for efficiency. Furthermore, it is observed that the efficiency, corrected for self-absorption, decreases with an increase in sample volume, as expected.