Study Of Radon Emanation And Migration In Particle Packing Emanation Media

Radon is inert gas that wildly exist in nature with a half-life period of 3.85 day.It can caused inner radiation when it was inhaled into hung.It seriously affects the public's physical and mental health due to its short-life daughters are particles and are easy deposited in body,Results from epidemiology show that radon concentration exceed a certain limit can cause to happen to cancer.Therefore,the measurement of radon exhalation of emanation media surface like houses,soil,mines and tailings ponds is of great importance.This paper starts from the "anomaly" of radon data obtained from two methods of open and closed charcoal chamber to measure radon exhalation rate in the field of uranium tailings dam.A numerical simulation method was used to study the effects of open and closed charcoal chamber radon exhalation rates on the surface radon migration of the gas medium by the commercial software FLUENT.Then in view of the existing method of measuring radon exhalation rate can only be spread in the freedom radon emanation medium,a method to calculates the radon exhalation rate of emanation media in seepage state has been put forward and was verified by designing experiment device.Finally,on the basis of the influence of seepage on radon exhalation rate,the mining method is constructed in the laboratory to study the practicability of by controlling the seepage(ventilation structure and ventilation mode of stope)and then to control the radon discharge and the amount of radon exhalation portion of blasted ore heap.In general,this paper mainly carried out three studies: 1)the influence of open and closed charcoal chamber radon exhalation rate measuring method on the radon migration in the surface and sampling device of the gas medium;2)how to measure the radon exhalation rate when seepage flow occurs in the emanation medium;3)to control the study of radon exhalation by controlling the seepage flow.The following research results are obtained for the three research contents:(1)Using computational fluid dynamics(CFD)methods to numerically simulate the exhalation rates of open and closed charcoal chamber and taking into account the sampling flow rate,the permeability of the emanating medium to be measured,and the average deuterium concentration of the gas-collecting hood.The following conclusions can be drawn from the influence of the concentration of the outlet hood on the outlet: 1)During the open-loop measurement of the exhalation rate,the sampling flow rate and the emissivity of the medium have a significant effect on the migration of the germanium in the emanation medium.In the open-loop measurement process,the average concentration of the helium collector and the outlet enthalpy concentration at the outlet of the hood are quite different.Therefore,when using the open-loop helium measurement method to calculate the helium deposition rate,the helium concentration should be corrected.2)During the closed loop measurement of radon exhalation rate,the average radon concentration of the hood and outlet radon concentration at the outlet of the hood are not changed at the same sampling time when the permeability of the medium to be measured increases from 10-10 m2 to 10-7 m2.Obviously,while the sampling speed is from 0.5m/s to 1m/s,the average radon concentration of the hood and the radon concentration at the outlet of the hood increase,but the increase does not exceed 2%.(2)In is set up in the laboratory to verify the method of radon seepage.The following conclusions are drawn: 1)When there is a seepage in the emanation medium,the radon exhalation rate on the surface of the emanation medium will increase with the increase of the seepage velocity.Experiments were conducted on the tailings as experimental samples and found that when the seepage velocity was increased from 30 ml/min to 300 ml/min,the radon exhalation rate on the emanation medium surface increased by 32.5%.2)The method for calculating the radon exhalation rate under the seepage condition proposed in this paper is indeed feasible.The calculated uranium leaching rate for different seepage velocities is also reasonable.(3)Set up an indoor mine retaining method stope model to study the influence of ventilation on the decantation of ore dumping,and the following conclusions have been obtained: 1)Different ventilation methods and different directions of wind affect the concentration of exhaust gas and thorium in the stope method.The concentration of wind blows decreases with the increase of the amount of ventilation air.Under the same ventilation air volume,the concentration of exhaust air in the descentional is less than the ascentional wind;the exhaust ventilation in the end ventilation(or ascentional wind)is greater than the central ventilation Downwind(or descentional).2)Different ventilation methods and wind directions affect the dialysis share by affecting the seepage of helium in the ore heap.With the increase of ventilation volume,the share of thorium exhalation increases.In the same ventilation volume and direction of wind flow,the share of helium accumulation in the central ventilation mine is smaller than that at the end.