Buffer material was the last artificial barrier of high-level radioactive waste repository,and its retardation capability to radioactive nuclides would directly affect the security and stability of the repository system.Bentonite was a suitable mineral,which can be used to build an integrated buffer material because of low hydraulic conductivity,good swelling and sealing properties,plasticity and high sorption capacity.Bentonite-zeolite-pyrite type integrated buffer material was constituted by the bentonite-zeolite-pyrite weight ratio was 63 ∶ 27 ∶ 10 (abbreviated as B7ZP),that zeolite and pyrite were chosen as mineral additives.Then constant source diffusion experiment was carried out to investigate strontium diffusibility in B7ZP with initial dry density of 1.70 g/cm3.The experimental results indicate that B7ZP has good retardation capability for strontium,and the apparent diffusion coefficient of strontium is 3.3×10-12 m2/s,smaller in B7ZP than in pure bentonite.The convection-diffusion-adsorption multi field coupling model for strontium migration was established based on the theory of porous media pollutant migration.MATLAB software was used to analyze migration distance of strontium in B7ZP under the condition of different time scales,seepage velocity,apparent diffusion coefficient and retardation factor.These research results can supply reference for usage of barrier materials and assessment of long-term retardation capability.%缓冲材料作为高放废物处置库中多重屏障体系的最后一道人工屏障,其对放射性核素的阻滞性能将直接影响到处置库的长期稳定性和安全性.以具有低渗透性和良好的膨胀自愈性的膨润土作为集成缓冲材料的基材,以沸石和黄铁矿作为矿物添加剂,三者按照质量比为63∶27∶10均匀混合构成集成缓冲材料B7ZP,并采用恒定源扩散实验分析了锶在于密度为1.70 g/cm3试样中的扩散特性,结果表明,B7ZP缓冲材料对锶具有良好的阻滞性能,其表观扩散系数为3.30×10-12 m2/s.同时,以多孔介质污染物迁移理论为依据,建立了锶在集成缓冲材料B7ZP中迁移的对流-弥散-吸附多场耦合方程,并应用Matlab软件分析了不同的时间尺度、渗流速率、表观扩散系数和阻滞因子等因素下集成缓冲材料B7ZP对锶的长期阻滞性能,为高放废物处置库的缓冲材料设计和长期阻滞性能评价提供科学依据.
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