| The study on nuclide migration behavior in geological disposal nuclear waste which is an important part of safely dispose of nuclear waste,can provide an effective reference for the site selection of waste disposal,and it is of great significance to the protection of human society and ecological environment.At present,most of the studies on the migration behavior of nuclide in the medium are based on the groundwater as the migration power and focusing on aqueous chemistry and elemental geochemical behavior,but there is no study on the effect of rising Geogas flow on nuclide migration after geological disposal.The effect of Geogas flow on the migration of deep matter is long and stable.For the long-term disposal of high-level waste in deep underground,the cumulative effect can not be ignored.This paper studies the law of nuclide migration in the geological disposal of nuclear waste under the action of Geogas by computational fluid dynamics simulation software——Fluent,and aims to evaluate the safety of the repository environment in a new way,which can provide some reference value for further study on the behavior of nuclide migration under Geogas as carrier.In this paper,the purpose of combining the simulation and experiment is to study the nuclide release,the migration,adsorption and retention in the medium.?1?The key factors influencing Uranium release are analyzed by Uranium migration experiment in lead-zinc mine and the saturation release rate and release ratio of U in inclusions are deduced.?2?In this paper,the trajectories,velocity distributions,heat transfer effects and pressure distributions of U3O8 particles in the near-field dielectric channel are studied though the simulation of the soil column experiment.?3?The influencing factors of Uranium migration in far field are analyzed by simulating multi-group contrast experiments.?4?The adsorption patterns of gas flow field which is composed of Uranium and Geogas flow in soil and granite are analyzed based on Gas-Solid adsorption theory.The following innovative research results are obtained:?1?The saturation release of Uranium in the inclusions is proportional to the Uranium concentration in the sample and the total volume of the model,which is inversely proportional to the sampling efficiency and sampling time.?2?The Discrete Particle Model in the saturated adsorption medium is established for the near-field migration behavior of Uranium.In the absence of wall adsorption,the movement of U3O8 particles in the near-field dielectric channel is affected by the flow of airflow.It is concluded that the retention of U3O8 particles in the medium is mainly affected by the particle size of the medium,the physical structure of the medium and the size of the model?flow length?though the analysis of factors influencing airflow and particle force.?3?The flow model of the fluid in porous media is established for the study of the far field migration behavior of Uranium.The migration of Uranium in the geological body is mainly affected by the factors such as the depth of the ore body,the grade of the ore body and the physical properties of the surrounding medium?particle size,density,pore size?.Located in the deeper ore body due to the greater the rate of gas flow and the more dynamic migration;large ore body in the release of U3O8 more,so in the same time more U3O8 enrichment in the surface;The medium particles with small particle size and small density have large internal surface area,so the same volume of medium can adsorb more U3O8 particles.?4?The adsorption of the gas stream composed of U3O8 particles and Geogas in the soil medium belongs to the BET multi-molecular layer adsorption,the adsorption in granite media belongs to Langmuir monolayer adsorption.For the same temperature of the adsorption,the greater the pressure the amount of adsorption?less than before the saturation adsorption?,when the c value is large and the system pressure is low,the adsorption of the multi-molecular layer will degrade into the monolayer adsorption.?5?It could provide some reference for the selection of the backfill material and the surrounding rock of the repository through the combination of the simulation of Uranium migration in the near-field and the far-field.The material should be selected as the backfill material with the smaller particle size,smaller density and slightly larger pore size,which has better adsorption effect on the nuclide in the air stream.The repository should be disposed in the deep rock mass with large particle size and dense structure,which can play a good blocking effect on the radionuclide in the Geogas flow. |
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