Theoretical study on the radon exhalation in the uranium tailings backfill

The paper is attempting to make a theoretical study on the radon exhalation in the uranium tailings backfill ground. As is done in the uranium mining practice,heap-leaching uranium tailings can be used as the filling material in the stopes to deal with the uranium tailings,which can not only help to reduce the pollution to the environment caused by the uranium tailings that pile on the ground-surface,but also can help to increase the security of the underground mined-out areas. In addition,when the uranium tailings are used as filling materials,the radon tends to decay from the residual radium in the tailings and exhale from its surface,which is likely to cause the pollution of the underground working environment. In order to ensure the security of the radiation environment to the underground workers,it is of a great urgency to study the migration regularity and the control measures of radon in the radium mine. It is just starting from this need that we have worked out the formulas and equations to calculate the radon exhalation rate on the surface of the filling system. What is more important,we have been trying to use the pure diffusion theory of radon in the media as two different situations. And,then,we have made an exploration of the effects of different physical parameters,including the water saturation,porosity and layer thickness on the radon exhalation of uranium tailings,under the conditions with the tailings medium porosity being 0. 3. Besides,we have also made an assessment that the radium activity concentration in the uranium tailings is 3 400 Bq / kg,whereas the dry uranium tailings emanation coefficient is 0. 1with the density of uranium tailings being 2. 5 × 103 kg / m3. As is shown in the results of our study,the emanation coefficient with no cover of the water saturation may tend to increase from 0 to 0. 25.Furthermore,the radon exhalation of uranium tailings has been found increasing first and then decreasing. Specifically speaking,when the water saturation increases from 0 to 0. 12,the radon exhalation rate of the uranium tailings tends to increase from 5 Bq /(m2·s) to 11 Bq /(m2·s). Furthermore,if the water saturation increases from0. 12 to 0. 25,the radon exhalation rate would go on reducing from 11 Bq /(m2·s) to 10. 5 Bq/(m2·s). Or,if the uranium tailings thickness is 3 m and the cover material porosity is 0. 05,the cover thickness may grow up from 0 to 0. 1 m,though the radon exhalation rate may turn to fall by 67. 5%. However,when the cover thickness increases to 0. 5 m,the radon exhalation rate may fall by 91. 8%.