Experimental Research On Soil Covering For Decommissioning Of Geological Exploration Facilities In An Uranium Mine

In the process of uranium exploration and technology utilization,exploration units have built many exploration facilities for scientific research and other purposes,although these facilities meet the needs of national defense and national economic development,but it has had an impact on the surrounding environment to a certain extent.Before the uranium geological exploration facilities were decommissioned,radionuclides had entered the environment through many ways,which had a certain impact on the surrounding environment and caused hidden dangers to human and animal safety.In order to eliminate the hidden dangers timely and effectively,it is urgent to decommission the uranium geological exploration facilities.According to the experience gained from the decommissioning treatment project of military uranium geological exploration facilities for many years,the waste rock pile of uranium geological exploration is the most difficult project with outstanding environmental impact in the treatment work,and its treatment workload and funds can account for more than 70% of the total project volume.Among them,radon exhalation and ? radiation from uranium mines have always been the focus of environmental treatment of uranium mine decommissioning.In-situ coverage is the most effective way to restrain radon exhalation and ? radiation from the surface of uranium waste heap,and it is also the key to the effect of decommissioning of all uranium geological exploration facilities.In order to work out the covering scheme of waste rock pile in uranium mine reasonably,it is very important to carry out soil covering test for the treatment of waste rock pile.In this paper,taking the waste pile of a uranium mine as the research target,through the coverage test of different covering materials to restrain radon exhalation rate in this area.It was studied the effect of different covering materials on restraining radon exhalation rate and the relationship between cover thickness and radon exhalation rate and ? radiation dose rate.As a result,the material with better covering effect is selected.The relationship between soil cover thickness and radon exhalation rate and ? radiation dose rate was obtained,the optimum cover soil thickness in this area was determined,and the action mechanism of soil cover on radon exhalation rate and ? radiation dose rate was analyzed.The results show that different mulches have different effects on restraining radon exhalation rate.From the reduction coefficient,it can be concluded that sandy subclay is better than sandy subclay + gravel(2:1),sandy subclay + gravel(2:1)is better than sandy subclay + sand(2:1),sandy subclay + sand(2:1)is better than gravel,and sandy subclay is determined to be the best covering material in this area.The radon exhalation rate decreases sharply with the increase of the thickness of the covered soil,and tends to be stable when the thickness of the covered soil reaches 45 cm.The radon diffusion coefficient decreases with the increase of compaction degree.The logarithmic correlation between coverage thickness and radon exhalation rate was fitted.The optimum cover thickness of the test site as a restricted open place is 68 cm,while that of an unrestricted open place is not less than 110 cm after decommission.The research results can provide technical parameters for the decommissioning treatment project of waste rock piles at exploration sites in this area and similar areas.