Study On Regularity Of Radon Exhalation In Acid Leaching Uranium Mines And Radiation Safety Protection In Mine Yard

There are a large number of uranium ore heaps in uranium mills.These uranium heaps usually carry a large amount of radon during the uranium leaching process.These radionuclides exhaled from the surface of the ore and the pores of the ore particles have an important influence on the radon concentration of the uranium mine yard.How to prevent radon from the uranium mine yard has become a major problem in the uranium mining and leaching process.Research indicates that the radiation dose of uranium mines workers mainly comes from radon and its radon progeny,so it is particularly important to do well the radon protection engineering of the uranium mine yard.Therefore,in this paper,by means of a combination of theory and experiment,indoor experiment is used to simulate the law of radon exhalation during the leaching of uranium deposits at the uranium mines yard.According to this law,the corresponding radon protection measures for uranium mine yard are put forward.The results achieved are as follows:(1)The theory of radon transfer in emanation medium and the theory of radon transfer in gas-liquid two-phase flow are presented.Radon migration in the emanation medium is mainly diffusion,seepage and diffusion-seepage in three ways,and in the gas-liquid two-phase flow,the transfer of radon is a complex phase transfer process.Radon exhalation rate is affected by the flow of gas-liquid two-phase in the uranium mine heap and the concentration distribution of radon in the two phases.(2)A one-dimensional uranium leaching experimental column was designed and made.The acid leaching experiment of uranium ore was carried out and the results show that: In the whole leaching reaction,the concentration of uranium ions in the leachate is at a low level in the initial stage of leaching,and it rapidly increases and then gradually decreases with the progress of leaching reaction,and finally tends to be stable;The p H of the leachate shows a gradual decrease throughout the leaching reaction,and the more late the leaching,the smaller the p H change in the leachate;During the whole leaching process,the change of radon exhalation rate firstly decreased rapidly and then slowly increased with the increasing of leaching rate;In the course of one day of spraying,the spraying intensity certainly-20.55 L/(h·m2),the radon exhalation rate on the ore heap surface gradually increases at the initial spraying,reaches the maximum value and then decreases gradually and tends to be stable;When the amount of spraying acid is equal to the liquid-exchanging,the radon exhalation rate of the initial stage of leaching(the first day)is the highest in the whole experiment,while the mid-term(the eighth day)and the later period(the fifteenth day)had a lower radon exhalation rate than the first day,and the fifth day had a relatively higher radon exhalation rate relative to the eighth day;At the stage of stopping the spraying and only liquid discharging,the exhalation rate of radon decreased first and then gradually increased to be stable.(3)According to the radon exhalation law,and combining the theory of safety system,the uranium mine yard radiation hazard factors were analyzed.The uranium mine yard radiation hazard have been analyzed based on FTA,taking "heap leaching of uranium ore heaps as radiation hazard" as the top event.In addition,the radiation protection measures for uranium mine yards are put forward.