Thoron Distribution profile of RRI thoron calibration chamber based on CFD simulation and its validation with measurement results

Dr. Mohammademad Adelikhah | Institute of Radiochemistry and Radioecology, University of PannoniaRiver Cree Ballroom 1

CFD is an inexpensive visualization tool that has been applied widely to solve health-related issues, such as predicting the activity concentrations of radon and thoron gas inside confined areas. Thoron gas is increasingly recognized as a potential source of radiation exposure in dwellings, so various organizations recommend assessing the long-term levels of indoor exposure (passive measurements). Obtaining accurate measurements requires determining the calibration factors for SSNTDs in order to predict the exact distribution of the thoron concentration inside a calibration chamber. Precise measurements are necessary to accurately assess radon and thoron dose exposure. Therefore, in the present study, the distribution of the thoron concentration was simulated and predicted inside the calibration chamber at RRI using different configurations for the inlet and outlet under various flow rates. The facilities at RRI were suitable for producing and sustaining the required homogeneous concentrations of thoron. Initially, the results showed that the transmission factor (Cout/Cin) increased after increasing the flow rate under all five chamber configurations tested in this study. The positions of the inlet and outlet, and the flowrate were also identified as key factors that determined the distribution of the thoron concentration within a closed volume, thereby affecting the transmission factor for thoron. The simulation results were also compared with the predictions obtained using the mixing model by defining the transmission factor (Cout/Cin), which can be used as a suitable indicator for checking the uniformity in terms of the distribution of the thoron concentration inside the chamber. Inconclusion, our results clearly demonstrate that the thoron calibration chamber at RRI is suitable for calibrating SSNTDs. Moreover, the CFD-based predictions agreed well with the experimental and analytical results according to the relative deviations and close agreement between the corresponding transmission factors in at higher flow rates.

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