COMPARISON OF THE BACKGROUND GAMMA-RAY SPECTRUM FROM SOIL OBTAINED BY DIRECT MEASUREMENT AND BY CALCULATION USING MCNP6 WITH NAI(TL) SCINTILLATION DETECTOR

Efficiency calibration is an essential part of any gamma-spectrometric or non-spectrometric measurement. The article describes all steps leading to the reconstruction of the gamma-ray spectrum from the soil - mathematical calibration of the NaI(Tl) detector and optimization of the model in the MCNP6 code, determination of radionuclide vector of soil around NPPs in Slovakia, calculation of the detector response matrix using the calculation code MCNP6 and finally the reconstruction of the gamma-ray spectrum. The results were compared in the energy range of 50-1620 keV for the spectrum obtained by direct measurement of the soil sample and for the spectrum obtained by calculation using the code MCNP6. The relative deviation in the whole spectrum between direct measurement and calculation is not more than 2%, which can be considered as the satisfactory result. The detector model thus created can be used to calculate the response matrix for any geometry arrangement.