Theoretical study of the exhalation of radon from a circular tubular cover layer
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Radium, which is naturally present in many rocks, decays to the radioactive gas radon, which is exhaled from the surface of underground tunnels and air-raid shelters and is a major source of human exposure to radioactivity. We developed a mathematical model for the migration of radon from a finite-thickness circular tubular emanation medium and a semi-infinite hollow cylindrical emanation medium based on the seepage–diffusion migration theory of radon in porous emanation media. We obtained an analytical solution for the distribution of radon concentration and a formula for the radon exhalation rate under steady-state conditions. When there was no seepage, the radon exhalation rate in the covering layer decreased as the thickness of the covering layer increased and tended toward zero. The radon exhalation rate from the covering layer increased as the radon diffusion coefficient increased. When seepage occurred, the difference in the radon exhalation rate between seepage and non-seepage decreased as the thickness of the covering layer increased. When v > 0, the radon exhalation rate in the covering layer increased as the seepage velocity increased. When v < 0, the radon exhalation rate in the covering layer decreased as the seepage velocity increased.
KeywordsRadon Mathematical model Seepage Diffusion Covering layer
PACS Nos.92.60.Sz 89.60.-k 23.60.+e
This Project was supported by National Natural Science Foundation of China (Grant No. 11575080), Hunan Provincial Natural Science Foundation of China (Grant No. 2018JJ2318) and the Graduate innovation subject of University of South China, China (Grant No. 2017YCXXM04).
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