Micro-release Mechanism of Radon in Underground Strata and Factors Affecting Its Emanation

Wei Zhang, Dongsheng Zhang, Wenmin Hu, Peng Li, Zhi Yang

Abstract


This paper begins with a discussion of the source and characteristics of radon, introduces the essence of damages caused by radon and its daughters, and China’s current radon-prevention limit standards. Theoretical analysis of the release of radon from a microscopic perspective highlights three main processes: emanation, migration, and exhalation. On this basis, the intrinsic and extrinsic factors affecting the emanation of radon are presented. Specifically, these factors include stratum lithology, radium nuclide content, pore size, porosity, particle size, permeability, emanation coefficient, air pressure, temperature, humidity, and wind velocity. Next, the progress of research into the external and internal causes of radon migration is reviewed. The external causes mainly include action of diffusion and convection, action of fluids in micropores, action of transportation by micro-bubbles, action of relay transmission, action of stress-strain, and action of deep-penetration geochemistry, while the internal causes mainly comprise the composite cluster theory and inherent action of itself. Finally, by reviewing the current research progress, we present prospects for research in the following five areas: prevention and control of the damages caused by radon and its daughters, the quantification of radon’s micro-release process, fractal characteristics of radon emanation, radon migration based on the combination of multiple mechanisms, and radon detection techniques in engineering application.


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