Numerical Simulation Of Ra-Rn Equilibrium Coefficient In A Sandstone-type Uranium Mine

In the process of exploration and mining of sandstone-type uranium deposits,the radon balance has been destroyed due to radon pressure.In order to accurately calculate the uranium reserves,the radium balance coefficient needs to be corrected.The differential equation of migration is based on the natural decay theory of radionuclides.In an ideal system,the natural decay of Ra,the concentration of radon remains unchanged at around40d,and the radon equilibrium is established.The transient process of radon migration from the ore layer to the borehole was simulated,and a numerical simulation method for calculating the radon balance coefficient using radon concentration was given.The following conclusions were drawn:(1)When Radon flows with liquid groundwater,the distribution of flow field will influence its movement,the fluid characteristics are controlled by the fluid velocity field,the pore fluid is affected by the outlet position and inertia force.The migration of radon in macroscopic strata is influenced by horizontal convection and effective porosity.The migration of radon is mainly in horizontal direction,and the vertical distribution of radon concentration is well defined,from the bottom up,the radon concentration gradually decreases.(2)In some conditions,convection migration is the main migration mode of Radon,the orientation of radon migration is influenced by the tendency of rupture zone,the location of rupture zone affects the migration velocity of Radon,and increases the vertical migration ability of radon.(3)During the migration of radon from ore bed to borehole,the migration process is continuous,mainly in the horizontal direction,the vertical migration of Radon is very small,and the radon concentration in borehole increases gradually,and tends to be stable after 60days.Based on the decay of radium in an ideal system,the Ra-Rn equilibrium coefficient P_Rn=0.891 is calculated by using the 40d radon concentration and the saturated radon concentration before the equilibrium is destroyed as the revised values of radium-radon equilibrium coefficient.The mud can absorb and shield radon.The calculated balance coefficient of radium and radon is P_Rn=0.803,and the balance coefficient of radium and radon is decreased.The calculated Ra-Rn balance coefficient is P_Rn=0.881,and the Ra-Rn balance coefficient decreases.The calculated radium-radon balance coefficient is P_Rn=0.907,after the hole is drilled,when there is a fault zone near the borehole,it is found that radon migrates from the fault zone.The existence of the fault zone has a great influence on the Ra-Rn balance coefficient.