Investigation of radiations penetration in aluminum used in reactor technology

Measurements have been carried out to determine the spatial and energy distributions of fast neutrons, total gamma rays and secondary gamma rays in aluminum as a reactor wide structural material. Experimental work was performed using one of the horizontal channels of the ET-RR-I reactor. For secondary gamma ray investigations, measurements were carried out for bare, cadmium filtered and boron carbide filtered reactor beams. Aluminum cylinders with a diameter of 100 mm and of different thicknesses have been used. Fast neutrons and gamma rays were measured using a neutron-gamma spectrometer with a stilbene scintillator. Discrimination against undesired pulses of neutrons and gamma rays was achieved by a pulse shape discrimination based on zero cross over technique. The measured pulse amplitude distributions of fast neutrons or gamma rays were transformed to neutron or gamma ray energy distributions using the differentiation method and the matrix correction method, respectively. The obtained data were displayed in the form of spatial fluxes and energy distributions and attenuation curves. Total fast neutron macroscopic cross sections, gamma rays linear attenuation coefficients and the relaxation lengths were obtained for the whole energy range and at different energies.