Computed tomography to evaluate the influence of the internal concrete structure on attenuation coefficients

Abstract

In this work, the influence of the internal concrete structure on linear attenuation coefficients was investigated. The attenuation coefficient of 15 different concrete samples, identical in mixing design, was measured with a narrow beam setup in an energy range of 609-2447 keV. Fluctuations of up to 16.8% in the measured attenuation coefficients were observed between the different samples. In order to attribute these fluctuations to the internal sample structure, Computer Tomography (CT) scans were made of each individual sample. The scans were incorporated into a Monte Carlo (MC) model of the attenuation setup. Results of the MC model closely match experimental values and the same fluctuating trend between the attenuation coefficients of the different samples was observed. The CT images revealed the presence of mortar at the beam location for samples with low linear attenuation coefficient values. Correspondingly, aggregates were found to be present at the beam location for samples with high attenuation coefficients. The impact of the internal concrete structure can play an important role in applications such as contamination depth profiling or activity determinations in nuclear decommissioning. Also for other applications in gamma-ray spectrometry, the proposed method of combining CT images with MC modelling can be a useful tool to improve the quantitative analysis of radionuclides. Especially for inhomogeneous samples or samples of irregular shape, the CT imaging can add value.