Simulation of gamma-ray Compton scattering in reinforced concrete using the Monte Carlo method

Abstract

Studies the differential gamma-ray scattering spectroscopy technique (DGSS) for detecting the size and location of a steel reinforcing bar in reinforced concrete by Compton scattering simulation using the MCNP-4A computer code. The contrast of the technique was examined to evaluate the results of the simulation. The contrast is defined as the ratio of differential spectrum, (the difference of the scattering spectrum of a concrete block and the scattering spectrum of reinforced concrete), to the scattering spectrum of the concrete block. In the simulation model, reinforced concrete with a dimension of 40cm x 40cm x 15cm, and 1cm-diameter of steel bar at the depth of 3 cm, was considered. To relate the scattering point to the detector location, the detector was assumed to be confined to a point. The DGSS technique was applied to evaluate the effect of the gamma-ray source energy, the detector position and the response for size and location of the reinforcing bar. It was found that 2 MeV gamma-ray source and 90 degree of scattering angle gave the maximum contrast value. For this particular simulation set up, it was found that contrast value increased with diameter of reinforcing bar and decreased with depth. It was also found that the contrast increased while the bar was inserted into the incident beam until it reached a value of about 0.173 at 2.914 cm insertion depth, then the contrast began to decrease and then stayed constant. These preliminary results could be used as a guide to design a prototype and predict its performance