KBS-3和VDH是高水平放射性废物长期地质处置的两种主要方法。KBS-3的设计概念是将高放废物储置于地下400-600米深度；VDH处置是将高放废物储置于距地表约2千米以下的区域，深度可达4-5千米。VDH处置方法最大的优点是：在深孔深处地下水几乎停滞不动，有效地阻止了可能泄漏的放射性物质进入岩石甚至上升到地平面。VDH处置概念中深孔缓冲-回填-密封技术面临的主要挑战之一是预测膨润土的成熟化行为。缓冲/回填体系的长期低渗性，以及成熟最终均质化是维护深孔密封稳定和阻止核素泄露的重要因素。本课题拟采用实验与理论建模相结合的方法，对VDH处置库中高庙子膨润土的成熟化行为及其长效性能进行研究。探索水在高庙子膨润土中的运动和膨润土体系的均质化发展，以期建立成熟化数学模型。模拟计算结果对预测高压实膨润土在长期处置过程中渗透密封性能的变化规律有重要意义，为高放废物处置缓冲回填材料的设计提供参考参数。

KBS-3 and very deep borehole (VDH) concepts are two major types of long-term geological disposal methods for high-level radioactive waste (HLW) isolating from the biosphere. The KBS-3V concept for isolating the HLW at the depth of 400-500 m, is the officially proposed option in Sweden and has been the subject of considerable research in the past few decades, while the VDH concept is about the HLW isolated under a depth of 2km in the 4 km deep bore hole with 800 mm diameter. The HLW boreholes have a spacing of individual holes of 200m for avoiding thermal overlap. The greatest merit of the VDH concept is that the almost stagnant groundwater in the deep boreholes prevents the transport of the possible release of radionuclides into the rock or up to the ground level. One of the major challenges for borehole sealing is to anticipate the maturation behavior of clay seals in the borehole. The ultimate homogeneity of clay seals is expected to stabilize the borehole and prevent possible leakage of radioactivity. In this project, the investigating of maturation of buffer-backfill clay in the HLW deep borehole will be performed. A numerical model will be proposed to simulate the maturation process, both the expeditious water transport and clay migration in the initial stage as well as the slow subsequent homogenization. By performing numerical simulations for various clay types as well as different combinations of dimensions and initial densities of mud and dense clay the maturation process and the end result can be theoretically studied thereby to be the reference for selecting a suitable design for buffer-backfill clay in HLW repository.