Aplicação do radioisótopo Cs-137 na técnica de atenuação de raios gama para o monitoramento de suspensões aquosas de densidades variadas

Abstract

This study aimed to establish the operating conditions of a gamma radiation detection system using a low-activity cesium-137 radioisotope, applied to the Gamma-Ray Attenuation (GRA) technique for monitoring high-density aqueous suspensions. Experimental parameters, including operating voltage, fine gain, lower and upper-level discriminators, counting time, minimum number of counts, and resolution time, were systematically adjusted to maximize the precision and reproducibility of the system. The initial calibration positioned the photoelectric peak at channel 238, whereas a second calibration centered the peak at channel 507, thereby focusing on the central region of the multichannel analyzer scale. During the experiments, the calibration constant β (1.3792) and the average resolution time τ′ (0.0180 s) were determined, and the Region of Interest (ROI) was defined based on the average full width at half maximum (FWHM). The system was validated through tests using a 30% (v/v) barite suspension, which was initially allowed to settle and subsequently resuspended by mechanical agitation. Measurements were conducted at different heights along the settled column, with an acquisition time of 1800 s per point, enabling the monitoring of volumetric solids concentration variations across the solid–liquid interface. The experimental results revealed a decreasing concentration profile with increasing height, consistent with the expected behavior of gravitational sedimentation. Overall, the system exhibited a stable and reproducible response in agreement with literature data, demonstrating the feasibility of the GRA technique as a non-invasive and reliable method for monitoring dense suspensions. It is concluded that the use of cesium-137 expanded the range of measurable concentrations and reinforced the applicability of the system to industrial solid–liquid separation processes.