Eu(Ⅲ)溶液对膨润土-砂混合物渗透性能影响研究

Research on effect of Eu(Ⅲ) solution on the permeability of bentonite-sand mixtures

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。

Radionuclides will transport to the biosphere after the overpack destroyed in the high-level radioactive waste(HLW) disposal repository. The hydraulic conductivity of buffer/backfill material plays an important role in evaluating the properties of the engineering barrier of HLW disposal repository. The permeability characteristics of Gaomiaozi bentonite-sand mixtures are studied by using the flexible wall permeameter and taking 2.0×10-5 mol/L Eu(III) solution as influent. The hydraulic conductivities are measured at K=(2.07-5.23)×10-10 cm/s. Test results show that there is no significant change in hydraulic conductivity of bentonite-sand mixtures, swelling with water, with the sand ratio ranging from 0% to 50%. Therefore, the requirement of low permeability for buffer/backfill material should be met by these mixtures. The effective clay dry density(ECDD) is used in this paper; and a good exponential relationship between volume swelling strain and ECDD and a linear-attenuation relationship between the logarithm value of hydraulic conductivity and ECDD of bentonite-sand mixtures are obtained. Compared with the distilled water, the hydraulic conductivities of bentonite-sand mixtures are smaller when influent is the 2.0×10-5 mol/L Eu(III) solution, which may result from the effect of influent viscosity.