Study On Hydrogeological Conditions Of Clay Rock Pre-Selected Section Of High-Level Radioactive Waste Repository

With the development of the nuclear industry,more and more radioactive nuclear wastes need to be properly placed.Because of the high toxicity,high radioactivity,and high heat generation rate,a method of placing the nuclear wastes in geological bodies 500 to 800 meters below the surface are currently recognized by various countries.Granite and clay rock are more recognized for the rock types of geological bodies.The research work of this paper relies on the research and development project for high-level radioactive waste geological disposal of the National Bureau of Science and Technology for National Defense undertaken by the East China University of Technology in 2015—"Study on Screening and Evaluation of Clay-rock Sections of Northwestern China for High-level Radioactive Waste Geological Repository".On the basis of comprehensive analysis of geological data such as fracture structures and drilling records,through field hydrogeological surveys,60 water samples were collected.According to the results of analysis and laboratory testing of the water samples,and combined the project data,the key work areas in Tamusu and Suhongtu has been carrying out analysis of hydrogeological conditions,which provide a scientific basis for the construction of a high-level radioactive waste repository.The research results of this paper mainly include:?1?The overall topography of the area is low in the northwest and high in the southeast.The slope of most areas in the study area is between 0 and 15°,and the relief of the terrain is less than 30m.The hydrogeological units in the area have a hydrogeological structure of“water-inlet-water-water-isolation”.The aquifer lithology are sandstone,pebbly sandstone,etc.The lithology of the water-retaining layer is mudstone and siltstone,and the water barrier performance is good.?2?The research area of Tamusu is located in the Tamusu five-level groundwater system.The system boundary is mainly bounded by uplifts and faults,which is a relatively closed groundwater system.The water chemistry type of the leading edge is SO₄·Cl-Na or SO₄·Cl-Na·Ca.The deep-lake environmental water chemistry type is Cl-Na and the local area is HCO₃-Cl-Na.?3?The study area of Suhongtu is located in the Ailitege five-level groundwater system.The boundary of the system is mainly bounded by bulges and faults,and has a relatively complete system of supplementary diameters and rows.The bedrock fissure water chemical type is HCO₃,anion multicomponent type water.The chemical type is mainly Cl·SO₄-Na or Cl-Na in the discharge area.?4?The differences of?D and?¹⁸O values of groundwater in the study area are significantly different from those of surface water,among which groundwater?D and?¹⁸O values are the smallest,and surface water?D and?¹⁸O values are the largest.The?D and?¹⁸O values of the water samples were mostly distributed at the lower right of the LMML line and deviated,indicating that the groundwater source is mainly atmospheric precipitation,and the groundwater is subjected to strong evaporation during the runoff from the recharge area to the discharge area.The oxygen drift in three groups of surface water samples occurred in the Tamusu research area,which may due to the thermal fluid activity in the Early Cretaceous magmatism in the study area.?5?There are two sections of groundwater-rich water in the Tamusu research area,namely the Wulanwuzhuer and the Zhaganhaolai water-rich section.The permeability coefficient of the rock mass is lower than that of 10^-10m/s.Two pre-selected areas were circled in two research areas,with a total area of 5700km²,delineating three favorable areas with a total area of 1038km².