Study On The Influence Of Temperature And Humidity Including Freeze-thaw Process On Radon Migration In Uranium Tailings

In recent years,with the rapid development of China’s nuclear energy industry,the demand for uranium will increase,and the problem of radon pollution caused by uranium tailings produced in the process of uranium mining will become more and more prominent.There are many factors affecting radon exhalation on the sand surface of uranium tailings reservoir,but there are few reports about the temperature and humidity change of freeze-thaw process on radon migration of uranium tailings.In this paper,the radon migration law of uranium tailings at different temperature and humidity was analyzed theoretically;The influence of radon exhalation rate and pore radon concentration at different depths on the surface of uranium tailings during cooling,freezing-thawing and heating were studied by using the tailings of uranium tailings reservoir in southern China as the test specimen.Finally,the change of stable radon concentration with temperature in the specimen column under sealing condition was studied,and the following conclusions were obtained:(1)The model of radon migration and diffusion under different temperature and humidity was established and the theoretical study was carried out.The results show that: When the temperature between 0℃ and 40℃ and the volumetric water content between 2% and 15%,the diffusion coefficient,pore radon concentration,surface radon exhalation rate and emanation coefficient increase with the increase of temperature;At the same temperature,the pore radon concentration increases with the increase of volumetric water content;At the same temperature,when the volume moisture content between 2% and 5%,the surface radon exhalation rate increases with the increase of the volumetric water content;When the volumetric water content was 5%,the radon exhalation rate was the largest;After that,the surface radon exhalation rate decreases with the increase of volumetric water content.(2)The surface radon exhalation rate and pore radon concentration at different depths of uranium tailings during cooling,freezing and thawing and heating were measured under different environmental humidity conditions.The results show that: At the same humidity,the radon concentration in the pores and the radon exhalation rate on the surface of uranium tailings decrease with the decrease of temperature;At the same temperature,the pore radon concentration and the radon exhalation rate on the surface of uranium tailings increase with the increase of environmental humidity.(3)The surface radon exhalation rate and pore radon concentration at different depths of uranium tailings during cooling,freezing-thawing and heating were measured under different volumetric water content.The influence of freezing-thawing process on the emanation coefficient of experimental samples was revealed by closed experiments.The results were as follows:1)Experimental results of radon concentration in pores indicate that:(1)Under the same volumetric water content,the radon concentration of pore decreases with the decrease of temperature,and the radon concentration of lower pore was always larger than that of upper pore;(2)When the temperature between 0℃ and 20℃,the relationship between radon concentration in upper or lower pores was as follows: volumetric water content 25.16%>12.58%>6.29%;(3)When the temperaturewas-10℃,the relationship between radon concentration in upper or lower pores was as follows: volumetric water content 12.58 %>25.16 %>6.29 %;(4)When the temperature was-20℃,the relationship between the radon concentration of pores in upper pores was: volumetric water content 12.58 %>6.29 %>25.16 %;the relationship between the radon concentration of lower pore was: volumetric water content 12.58 %>25.16 %>6.29 %.2)The experimental results of surface radon exhalation rate show that :(1)Under the same volumetric water content,the surface radon exhalation rate decreases with the decrease of temperature;(2)Under the same temperature,the relationship between the surface radon exhalation rate was 12.58%>6.29%>25.16%.3)During the freezing period of the closed experiment,with the decrease of temperature,the emanation coefficient decreases and the stable radon concentration decreases.During melting,with the increase of temperature,the emanation coefficient increases and the stable radon concentration increases.