The Interaction Between Natural Water And Granite In Beishan Preselected Area Of High-level Radioactive Waste Disposal Repository

At present,multi-barrier deep geological disposal is the most feasible method for safe disposal of high-level radioactive waste.However,the groundwater in the depth will not only erode the surrounding rock,but also become the medium for nuclides to spread to the surrounding environment,threatening the safety of the disposal repository.This paper takes the Beishan Xinchang key sections as the research area.By collecting granite samples from Beishan Xinchang key sections and natural water samples that may replenish Beishan groundwater,carried out the water-rock interaction test under different temperature and pressure conditions,and analyzsis the change of the hydrochemical composition of the test solution and the oxide composition of the rock sample,?sing the method of principal component analysis and the saturation index of hydrogeochemical action in the process of analyzing the test,and the test solution and the Beishan deep borehole water chemical characteristics comparison of groundwater,comprehensive speculation of Beishan key sections is sure to deep groundwater recharge source,It also provides theoretical support for determining the ca?se of groundwater in the high-level radioactive waste disposal reservoir.Through the test of Qilian mountains surface water,Yinaoxia shallow groundwater and Qianhong spring water interacting with granite under different temperature and pressure,the following understanding can be obtained:The test conditions are normal temperature and pressure(25?C,0.1 MPa):In the experiment of interaction between Yinaoxia shallow groundwater and granite,the water-rock interaction was dominated by the dissolution of sodium feldspar and calcium feldspar and the formation of calcite precipitation.The Qilian mountains surface water with granite test in addition to the above three kinds of hydrogeochemical action,and weak potassium feldspar dissolved.The dissolution and precipitation of calcite mainly occurred in the interaction test between qianhongquan and granite in Hexi corridor.The test simulates the condition of groundwater circulation for 2km(55°C,10 MPa):The dissolution and calcite precipitation of sodium feldspar,calcium feldspar and potassium feldspar were further strengthened in the Qianhong spring water with granite interaction test and Qilian mountains in Hexi corridor surface water with granite interaction test In the Yinaoxia shallow groundwater and granite interaction test,the dissolution of sodium feldspar,calcium feldspar and calcite precipitation were the main factors.The test simulates the condition of groundwater circulation for 4 km(100°C,10MPa):Hydrogeochemistry of the three groups in the water-rock interaction test with different initial water samples was dominated by the hydrolysis of feldspar,quartz and biotite and the precipitation of calcite.According to the relationship between the main oxides and the components of solution ions in the test rock samples,the components in the process of interaction between groundwater and granite are from strong to weak under the influence of water-rock interaction:Na⁺?Ca²⁺?K⁺?Mg²⁺?Si⁴⁺and Al³⁺.Quartz,feldspar,biotite and calcite solubility increases with temperature rise,the solubility of quartz by the"salt effect"and the influence of p H rise significantly,"the same ion effect"can significantly inhibit the hydrolysis of feldspar minerals,sialic acid salt content by hydrolysis resistance began to in the order:black mica,potash feldspar,sodium feldspar,calcium feldspar.The contents of p H,TDS,Sr and other water chemical components of the water-rock interaction test solution were compared with the groundwater in the depth of Beishan borehole,combining with mineral saturation index and the variation trend of vario?s parameters in the test,comprehensive think the Yinaoxia shallow groundwater goes through a groundwater cycle with a depth of about 2 km and then supplies to the deep groundwater in the key research area of Beishan Xinchang.To sum up,the deep groundwater in the Beishan Xinchang key research area is supplied by the Yinaoxia shallow groundwater,and the main water-rock interaction in the runoff process is the dissolution of sodium feldspar,calcium feldspar and calcite precipitation.