Technetium-99m as a Tracer for the Liquid Residence Time Distribution Measurement: Optimization of Different Radiotracer Parameters for Flow Meter Calibration

Abstract

Flow meters are essential part of equipment in almost all chemical and process industries. Knowledge of the flow dynamics and flow of material through the reactor system is required to evaluate the performance of the reactors, processes, operation and design. Traditionally this evaluation can be performed using chemical tracers. Chemical tracer results are not always precise and they could not allow an online diagnosis. The samples containing chemical tracer have to go to a lab for analysis and chemical tracers are less sensitive than radioactive ones. Radioactive tracers are the only tracers capable of measuring the active residence time distribution (RTD) with high degree of precision and give information on-line without stopping the process. In this work the application of radiotracer method for RTD measurement in flow meter calibration is described. The RTD measurements of the system were performed in pilot-scale perfect mixer in series reactor for flow meter calibration with Technetium- 99 m (99mTc) as a radiotracer in the form of pertechnetate ion (99mTcO4 -). The optimization of the parameters included input signal of radiotracer, concentration of radiotracer and position of detectors. The measured data were analyzed, and standard and relative deviations were quantified under different operating conditions. A plug flow model was used to simulate the measured RTD curves and investigate the flow dynamics of the flowing water. The results of the study showed that the optimum concentration of 99mTc for flow meter calibration was 0.3 ml having activity 0.68 mCi. The standard deviation was σ=0.10 l min-1 and the relative deviation was 0.94%. The results of the study can help in the operation and design of the existing systems and design of new ones.