Characterization and applications of a walk-in-type mud test house for radioactive gas studies

A mud test house has been constructed at NIT Kurukshetra, Haryana, India, for facilitating studies requiring controlled dispersion of radon/thoron gases and decay products at relatively higher concentration. This manuscript discusses the design specifications, characteristics, and the projected applications for this test house. With a total internal volume of 7.5 m³ appropriate for a walk-in configuration, it serves as a compact yet functional facility ensuring high and stable concentrations of radon/thoron gases while maintaining cost effectiveness and easy parametric control. Dry mud bricks have been used in the construction after ascertaining their higher radioactivity content and radon exhalation rate in comparison to other available options. In the closed configuration, test house can provide radon concentration up to ≈ 250 Bq m^-3 which is approximately 5 times higher than the ambient levels of the same location. This corresponds to maximum equivalent equilibrium radon concentration of 52 ± 1.45 Bq m^-3. Maximum thoron and equivalent equilibrium thoron concentration measured by passive technique at 71 ± 8 and 4 ± 1.70 Bq m^-3 respectively makes it suitable for thoron dynamic studies as well. The test house has been designed to manifest different levels of ventilation rate and aerosol concentration, tuned for different kinds of studies requiring diverse experimental conditions. Results of characterization experiments performed on radon/thoron gases and decay products as a function of a few chosen aerosol and ventilation rate characteristics have been presented in this work. Levels of parameters and their control make the test house a reliable and adaptable geometry, ideal for studying the dynamics of radon/thoron gas and decay products, serving as an experimental facility to validate theoretical estimates and acting as a calibration chamber.