NUKLEONIKA 2006, 51(Suppl. 2):s21-s25

Of major concern are the self-absorption correction factors C_s in precise gamma-ray spectrometry of environmental samples. The overview of C_s determination methods (experimental, Monte Carlo calculations, analytical function application) is presented. Among several available methods, the author chose the one proposed by Debertin where the uncertainty level of C_s correction factor is 1-2%.
The point-like detector model is assumed whilst its efficiency is taken to be proportional to the weighted sum (integral) of the number of photons coming from sample volume elements. Computer program was developed to support the computation of C_s by the Debertin’s method for samples in cylindrical geometries and Marinelli beakers. The input data are sample dimensions, density and the mass attenuation coefficient. The C_s uncertainty due to an arbitrarily chosen position of a point-like detector would not exceed 1% for the considered photon energies and the sample density range.
Utilising this computer program, the relationships C_s(E,r) were obtained for the applied geometries and a SiO₂ matrix to support routine measurements. The SiO₂ matrix is widely encountered in environmental spectrometry. This relationship was derived by fitting the computed data with the function C_s(E,r) in the form proposed by Bolivar. It was shown that while handling this function to samples with the H₂O matrix, the error involved in estimations would not exceed 3%.