| Vigorously developing nuclear energy is an inevitable trend in our country.It can be predicted that the nuclear waste in our country will show explosive growth in the coming years,and the establishment of a geological repository of nuclear waste has also reached the point of urgency.The study of nuclide migration behavior in nuclear waste from geological repository is an important part of the safety evaluation of nuclear waste disposal,which can provide reference for the site selection of waste disposal.At present,most scholars mainly study the migration behavior of radionuclides in geological disposal environment using water as the medium.The geological environment is a complex process,especially for the high activity and heat release of the high-level radioactive waste itself,and the repository itself.It may be several hundred kilometers underground,forming a complex field under the action of temperature field and radiation field.Therefore,it is necessary to carry out diversified research on radionuclide migration in geological environment.In this paper,the migration and retention behavior of radionuclides in soil were investigated by using the geo-flow as the carrier of radionuclide migration,and the migration mechanism of the nuclides under the air flow was discussed.(1)The model of geo-gas migration column is established,and the feasibility of radionuclide migration behavior under the action of earth atmosphere is discussed by means of neutron activated nuclide simulating nuclear waste and radioactivity detection method.(2)Numerical simulation of gas flow,adsorption and transfer of matter and heat transfer of porous media under saturated porous media by using multi-physical field coupling simulation software.The migration and retention of nuclides in porous soil were studied under different conditions.(3)The migration and retention of nuclides in different media,different heights and different storage modes were investigated in laboratory by using the soil column model.The reliability of the computer simulation mathematical model is verified by comparing the results with the results of the multi-physical constant coupling model.In this paper,a natural contrast test was carried out to study the far field migration of nuclides in Yuebei Guangdong province.The main achievements of this thesis are as follows:(1)Through the establishment of the soil-column experiment model under different conditions,the following new rules are found:the four kinds of simulated nuclear species have the highest migration capacity in the soil:Sr,Ce,La,U.The retention of the Ce element is the strongest,and the retention capacity of La element is the weakest.The amount of nuclear migration after curing is obviously weaker than that of the uncured nuclear element,and the solidification treatment has obvious effect on the migration of the blocking nuclides.(2)The conclusion is that the mass concentration of nuclides decreases exponentially with the migration distance.The initial mass concentration had little effect on the migration ability of nuclides in soil,and the gas flow rate had a great effect on the adsorption and retention of nanoparticles in soil.Porous media with high porosity has strong retention ability to nuclides.(3)the natural analogy experiment proves that the nuclide in the natural concealed orebody can rise to the near surface through the dense surrounding rock.The magnitude of migration is positively correlated with ore body grade,but not directly related to the depth and thickness of orebody,but the abnormal amplitude of deep orebody is larger.The dip angle in the occurrence of ore body has an effect on the abnormal amplitude of U element,and the dip angle of the concealed orebody with the abnormal amplitude of 1.8-5.0 is mostly between 70°-78 °. |
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