A simple and inexpensive design of radioactive source for accurate level and height gauging in petrochemical industries

Radiation sources are used for measurement and control of industrial processes, determining the height of materials inside the vessel, analyzing the composition and structure of materials, and detecting defects in industrial processes due to the complexity of the production process. In petrochemical industries, the height of urea in a vessel can be measured using the nuclear level gauging method, which is a non-destructive technique. Therefore, the energy of the gamma emitting source, the design, and arrangement of the source geometry (including the point or rod sources), and the detector material (NaI (Tl) crystal or plastic scintillator) are crucial parameters. In this research, a nuclear level gauge, including the source, detector, and reactor containing urea and gases at high temperatures and pressures, was simulated by MCNPX Monte Carlo code and the results were compared and validated with experimental values. Then, the detector's response was evaluated and optimized based on the different arrangements of the radioactive source and its distances, as well as the type and geometry of the detector, and the best arrangement was selected. The comparison of the simulation results and the resulting analysis indicated that using point sources at specific distances (three points) instead of rod sources is a viable alternative due to its simpler structure, higher accuracy and stability, and lower production cost compared to the high cost of rod sources. Additionally, for accurate level and height gauging, rod detectors should be replaced with point detectors.