Identification and determination sources of uncertainty in measurement of activity in soil matrix

Environmental monitoring, which is an inseparable component of nuclear safety, is always important. The need for regular, accurate and qualified implementation is essential. The gamma spectrometry method is widely used for the detection and measurement of gamma emitting radionuclides in natural samples. In the gamma spectrometry method, like all methods of measurement, the determination of measurement uncertainty is evident. The aim of this study is to measure the gamma-ray radionuclide activity of the soil sample and the correct associated uncertainty. A soil sample in a cylindrical container and weighing 243 grams was used based on the 661 keV peak of cesium and a high-purity germanium detector (80% relative efficiency) for calculations. According to the counting of 72000 second of the soil sample, the amount of cesium activity was 482 Becquerel. Also, the uncertainty of the above activity measurements was calculated 33.4 Becquerels. The results of this study indicate that the measurement of activity of gamma emitting radionuclide with relative uncertainty of 6.9% indicates the high reliability of the results. Also in the total uncertainty, the counting and efficiency uncertainty make the main contribution.