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在高放废物处置库长期运营过程中包封容器将发生破坏,核素会向外界迁移,缓冲回填材料的水力传导系数是评价处置库工程屏障性能的重要指标。采用柔性壁渗透仪,研究2.0×10-5 mol/L的Eu(III)溶液作为渗入液时膨润土-砂混合物的渗透特性。结果表明,膨润土-砂混合物的水力传导系数K=(2.07~5.23)×10-10 cm/s;在0~50%掺砂率范围内,膨润土-砂混合物吸水膨胀过程中渗透性能随掺砂率增大时没有明显的变化,能够满足高放废物处置库缓冲回填材料低渗透性的要求。使用有效黏土密度的概念,得到膨润土-砂混合物的体积膨胀率随初始有效黏土密度的增大呈指数增大的趋势;混合物水力传导系数的对数值与有效黏土密度存在良好的线性衰减关系;与蒸馏水相比,渗入液(ECDD)为2.0×10-5 mol/L的Eu(III)溶液时,膨润土-砂混合物的水力传导系数较小,可能是由于渗入液黏滞性的影响。
During the long-term operation of a HLW disposal repository, the encapsulated containers will be destroyed and the radionuclides will migrate to the outside world. The cushioning of the hydraulic conductivity of the backfill material is an important indicator for evaluating the performance of the project’s barrier. The infiltration properties of bentonite-sand mixture with 2.0 × 10-5 mol / L Eu (III) solution as infiltrant were studied by flexible wall permeation instrument. The results show that the hydraulic conductivity of bentonite-sand mixture is K = (2.07 ~ 5.23) × 10-10 cm / s. The permeability of bentonite-sand mixture in the range of 0 ~ 50% There was no obvious change when the rate was increased, which could meet the requirement of low permeability of buffer backfill materials in HLW repository. Using the concept of effective clay density, the volume expansion rate of bentonite-sand mixture tends to increase exponentially with the increase of initial effective clay density. There is a good linear attenuation relation between the logarithm of the hydraulic conductivity coefficient of the mixture and the effective clay density. When the ECDD was 2.0 × 10-5 mol / L Eu (III) solution, the hydraulic conductivity of bentonite-sand mixture was small, probably due to the viscosity of infiltrated liquid.