Development of evaluation for swelling characteristics of bentonite based buffer under water-chemistry condition of high level radioactive waste disposal facility

核电厂排出的高放废物处置是21世纪亟待解决的重要问题。在这个计划中，有一种材料，被称为“膨润土基缓冲材料”的多个屏障之一。膨润土基缓冲材料填补了废物容器和周围基岩之间的空间，而且由于废物的运输方便，有可能在海岸带附近建造处置设施。为了对这一项目做出贡献，本研究旨在定量评价膨润土基缓冲材料在海水条件下的自密封行为，并从海水条件下自密封性能的角度建立膨润土基缓冲材料的设计方法。这个实验是一维的…其次，具体考察了影响自封闭行为的因素，通过测量Na^+、Ca^&lt；2+&gt；2+&gt；2+和gt；此外，根据本实验结果建立了缓冲材料在蒸馏水条件下的自封闭行为的经验方程，以预测和评价“溶胀行为的评价方程”，从而建立了海水条件下可感知的自封闭行为方程。本研究的新发现如下：1.在以下条件下，通过本次自封闭试验了解到海水对自封闭行为的影响很小。在膨润土A中，如果间距为1.25 mm或更小，且提供的溶液浓度为海水浓度的100%或更小，则可以理解为海水的影响很小。而在膨润土B和E中，如果间距为1.25 mm或更小，提供的溶液浓度为海水浓度的10%或更小，则认为海水的影响很小。2.研究表明，海水条件下缓冲材料的空间没有渗透海水是导致自封性能下降的原因之一。认为蒙脱石结晶层对海水中阳离子的过滤能力是这一机理。3.尽管在本实验条件下的适用性有限，但通过将基于本实验结果的经验方程建立为“Komine和Ogata评价膨润土膨胀行为的方程”，得出了在海水条件下可感知的自密封行为方程。4.综合上述结果，从海水条件下自密封性能的角度出发，构建了设计方法。较少

Disposal of high-level radioactive wastes exhausted from nuclear power plants is an important problem that should be solved in the 21st century. In this plan, there is a material that is called"Bentonite based buffer material"in one of the multiple barriers. Bentonite based buffer material fills up a space between waste container and surrounding bedrock Moreover, a disposal facility has the possibility that is constructed in the vicinity of the coastal zone by the convenience of the wastes form transportation.To contribute this project, this study aimed to evaluate the self sealing behavior of bentonite based buffer material in the seawater condition quantitatively, and to establish design method of bentonite based buffer material from a viewpoint of self-sealing property under seawater condition.In this study,"self-sealing test by the one-dimensional model"was done in the beginning, and the self-sealing behavior in the seawater condition was investigated. This experiment is one-dimens … More ional model test to imitate the self-sealing behavior of seawater condition by installing a space that scales down the relation between the space part of an actual disposal site and the buffer material in the one dimension, and supplying artificial seawater of a different concentration.Next, the factor thought to be influence on the self sealing behavior was investigated Concretely, the invasion situation of the seawater element in the pore water of the specimen was investigated by measuring each cation exchange capacity (EXC) and exchangeable cation (CEC) of Na^+, Ca^<2+>, K^+, and Mg^<2+> ions in the specimen after it experimented.In addition, the equation that was appreciable of self-sealing behavior under seawater condition was made by building the empirical equation based on the result of this experiment into the self-sealing behavior of the buffer material in the distilled water condition to forecast and appreciable"equations for evaluating the swelling behavior".The new finding obtained for this research is shown below.1.In the following conditions, it has been understood that influence of seawater on self-sealing behavior is small from this self sealing test. In the bentonite A, if the space is 1.25mm or less and concentration of supplied solution is 100% or less of sea concentration, it has been understood that influence of seawater is small. And in the bentonite B and E, if the space is 1.25mm or less and concentration of supplied solution is 10% or less of sea concentration, it has been understood that influence of seawater is small.2.It was shown that there was a possibility because of seawater was not infiltrated in the space of the buffer material as one of the reasons for the decrease in self-sealing behavior is small under the seawater condition. The filter ability of cation in seawater by montmorillonite crystalline layer is thought as this mechanism. And it is thought that this function works effectively by hardening the bentonite well-set.3.Though the applicability was limited in this experiment condition, the equation that was appreciable of self sealing behavior under seawater condition was made by building the empirical equation based on the result of this experiment into"equations for evaluating the swelling behavior by Komine and Ogata".4.Synthesizing the above-mentioned result, design method was constructed from viewpoint of self sealing property under seawater condition. Less