Preparation of a radon-free thoron source for a thoron calibration chamber

Development of a thoron calibration chamber based on computational fluid dynamics simulation and validation with measurements

Recently, interest in measuring the concentration of 220Rn in air has increased greatly following the development of standards and the calibration of monitoring instruments. In this study, a 220Rn calibration chamber was designed and developed at the Institute of Radiochemistry and Radioecology (RRI) based on the computational fluid dynamics (CFD) method implemented in ANSYS Fluent 2020 R1 code at the University of Pannonia in Hungary. The behavior of 220Rn and its spatial distribution inside the 220Rn calibration chamber at RRI were investigated at different flow rates. The 220Rn concentration was close to homogeneous under higher flow regimes due to thorough mixing of the gas inside the chamber. Predictions based on CFD simulations were compared with experimentally measured transmission factors (Cout/Cin). The spatial distribution of 220Rn was dependent on the flow rate and the positions of the inlet and outlet. Our results clearly demonstrate the suitability of the 220Rn calibration chamber at RRI for calibrating monitoring instruments. Furthermore, the CFD-based predictions were in good agreement with the results obtained at higher flow rates using experimental and analytical models according to the relative deviation, with a maximum of approximately 9%.

Intercomparison on the measurement of the thoron exhalation rate from building materials

Thoron (²²⁰Rn) exhalation from building materials has become increasingly recognized as a potential source for radiation exposure in dwellings. However, contrary to radon (²²²Rn), limited information on thoron exposure is available. As a result no harmonized test procedures for determining thoron exhalation from building materials are available at present. This study is a first interlaboratory comparison of different test methods to determine the thoron exhalation and a pre-step to a harmonized standard. The purpose of this study is to compare the experimental findings from a set of three building materials that are tested, and to identify future challenges in the development of a harmonized standard.