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 s pectrometric measurement systems that calculates the total efficiency for any axially symmetric arrangement of source and detector. This met hod is now discussed in more detail for the complex case Marinelli bea ker 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 be en determined and found to agree very well. The degree of self-attenua tion effects is determined principally by the energy of the photon, de nsity of the sample material and the average path length of the photon s in the volume source. Chemical properties have only a negligible inf luence. The analysis described here includes experimental and theoreti cal 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 wa s used. The densities of the sources ranged from 0.5 to 1.6 g/cm3, cor responding to the expected densities of environmental samples. The ave rage path length of the photons in different volume sources was calcul ated by the Monte Carlo code and from this value the correction factor for the self-attenuation was derived.