Study Matrix Densities Variation on Assay of 137Cs & 60Co using Gamma Spectrometric Analysis and Correction Equation

Abstract

Abstract There are many factors affecting the results of specific activity determination by using HPGe detection system. One of these important factors is the incompatibility and dissimilarity between the density of the certified standard source for efficiency calibration of the system and the samples to be measured. In this work, five standard samples containing 137Cs at 661.6 keV and 60Co at 1173.2and 1332.5 keV energies, with the same geometry and different densities were used to investigate and validate the percentage of error. It is scientifically known that the low energies are attenuated more than the high energies. The densities of the used standard samples are 0.7, 1, 1.2, 1.3, 1.6 g/cm3 respectively. The detection system was well calibrated before carrying out the measurements. The calculated error percentages between the measured activities (in Bq) and the certified values for 137Cs and 60Co in the standard samples were found to be in wide range from 9.8% to 19.2% for 137Cs and from 7.77% to 16.1% for 60Co respectively. A correction equation taking into consideration the densities variation was suggested and formulated to overcome and compensate these errors.