TESTING OF DIFFERENT TRUE COINCIDENCE CORRECTION APPROACHES FOR GAMMA-RAY SPECTROMETRY OF VOLUMINOUS SOURCES

To achieve the highest possible sensitivity of analysis for environmen tal samples it is common practice to use both a high efficiency detect or and a close measurement geometry with a large sample size (e.g. Mar inelli beaker). Under such conditions, the typical efficiency calibrat ion procedure results in a biased activity value for many nuclides due to the true coincidence summing effect. While there are a few methods to correct for this effect with special calibration standards, such c alibrations can be both time consuming and expensive. Due to these cal ibration difficulties, the true coincidence summing effect is often si mply ignored. Recently, it has been demonstrated that the coincidence summing correction can be performed mathematically even for voluminous sources. This new method consists of an integration of the coincidenc e correction factor over the sample volume while taking into account i ts chemical composition and the container. In this paper, we will disc uss the latest approaches for establishing the peak efficiency and pea k-to-total efficiency curves, which are required for this method. Thes e approaches have been tested for HPGe detectors of two different rela tive efficiencies.