Dedicated Monte Carlo Procedures Applied in Gamma- ray Spectrometry Used in Decommissioning of Nuclear Facilities

Because the experimental efficiency calibration is limited to several measurement geometries and cannot be applied directly to all measurement configurations, the efficiency transfer method for the efficiency computation was applied using ETNA software. An approach using efficiencies measured with point sources combined with theoretical procedures was applied for obtaining the peak efficiency ε(E ) for disk sources measured with a NaI(Tl) detector. The transfer method was applied for the computa‐ tion of the efficiency of an HPGe detector using as a reference a point source placed at 10 cm height from the face of the detector. The method was applied both for point sources and volume sources with varied compositions and densities. To correct the experimen‐ tal values of the efficiencies, coincidence summing effects were evaluated using GESPECOR Monte Carlo code. The study of the response function characterization of the ISOCART and Segmented Gamma Scanner WS1100 gamma-ray spectrometry systems was related. GEANT 3.21 Monte Carlo code was used to simulate the spectra expected to be obtained for the photon energy range from 50 to 2000 keV. A big volume represent‐ ed by a 220l cylindrical source was considered to be measured with the two systems. The full energy peak efficiency and the total efficiency were evaluated.