عنوان مقاله [English]
A useful benchmark for the reliability of gamma spectrometry results is to provide measurement uncertainty. Due to the importance and necessity of radiation monitoring in water resources, the aim of this research is measuring the gamma emitting radionuclides along with the expression of uncertainty in these measurements. To calculate the uncertainty of activity measurements in water, a sample which its radioactive elements were prepared from the PolAtom Company was used. The calculations were performed based on the 661 keV peak of 137Cs radionuclide and a high-purity germanium detector (HPGe). The investigations show that the factors affecting the measurement uncertainty are composed of two parts, including counting with the gamma spectroscopy system and sample preparation that each of these parts comes from several sources of uncertainty such as uncertainties associating in the counting process, efficiency calibration, emission probability, the counting correction factors, and the mass measurement. The measurement results show that the relative uncertainty is about 3% (Coverage factor = 1) for a water sample with an activity of 425 Becquerel from 137Cs.