APPLICATION OF A NEW MONTE-CARLO METHOD FOR DETERMINATION OF SUMMATION AND SELF-ATTENUATION CORRECTIONS IN GAMMA-SPECTROMETRY

A new Monte Carlo method [1] has been previously described for gamma spectrometric measurement systems that calculates the total efficiency for any axially symmetric arrangement of source and detector. This method is now discussed in more detail for the complex case Marinelli beaker and detector. The logic of the technique is explained with the aid of flow charts. For two different Marinelli beakers and nuclides both the theoretical and experimental summation correction factors have been determined and found to agree very well. The degree of self-attenuation effects is determined principally by the energy of the photon, density of the sample material and the average path length of the photons in the volume source. Chemical properties have only a negligible influence. The analysis described here includes experimental and theoretical determinations of self-attenuation correction factors for defined arrangements. In the experiments a gamma standard solution containing several radionuclides covering the energy range from 88 to 1836 keV was used. The densities of the sources ranged from 0.5 to 1.6 g/cm3, corresponding to the expected densities of environmental samples. The average path length of the photons in different volume sources was calculated by the Monte Carlo code and from this value the correction factor for the self-attenuation was derived.