STUDIES OF THE INFLUENCE OF THE LEAD SHIELDING GEOMETRY ON THE GAMMA SPECTRA MEASURED BY THE LOW BACKGROUND SPECTROMETER SYSTEM USING THE HPGE DETECTOR

Abstract

In the measurement of gamma spectra by the low background gamma spectrometer system using the HPGe detector, lead shields have been often used for preventing from gamma rays in background radiation. Rely on the laboratory facilities, lead shielding geometry can be different. Gamma rays from the measured radioactive source interact with matter as the lead shield, then enter the HPGe detector and contribute the backscattering area of the gamma spectrum. Basing on that, this work presents estimating the influence of the lead shielding geometry on the gamma spectra. The MCNP5 code was used to simulate the gamma spectra of 137Cs, 54Mn, 60Co and 22Na measured by the gamma spectrometer system with the lead shield having cylinder or square prism shape. The effectiveness of simulation modelling based on the MCNP5 code was validated by comparison of experimental and calculated gamma spectra. The results showed that using the lead shield shaped cylinder, backscattering gammas contribute from 3.68% to 5.23% more than using the lead shield shaped square prism.