Characteristics of Fiber Reinforced Concrete as Barrier Materials for Nuclear Waste

本文研究了纤维混凝土作为核废料防护材料的工程性能。主要研究结果如下：1.为了确定混凝土的合理渗透性，研究了基于NaCl溶液渗透深度和有限元分析的方法。虽然在常规方法中需要一周以上，但是通过使用相同的设备，本方法需要一天左右。在以前的研究中（去年），渗透率的分析是基于一维精确解。为了考虑试件几何形状的影响，提出了基于有限元分析的修正方法，并确定了钢纤维混凝土的渗透系数。结果表明，与普通混凝土相比，纤维对混凝土的渗透性能没有特别的影响.发展了基于有限元法和边界元法的数值计算方法。通过对裂变产物扩散过程的模拟分析，发现在近地表附近，扩散作用有限，而对流作用对裂变产物的分布影响很大。因此，低渗透率的材料是理想的屏障。在综述国内外声发射监测技术发展现状的基础上，指出了声发射监测的重要性。其次，为研制裂纹监测装置，对声发射波形分析进行了基础研究。

In the present research, the engineering properties of fiber reinforced concrete are studied, as barrier materials for nuclear waste. Results obntained are described, as follow ;1. To determine the plausible permability of concrete, the method based on the seepage depth of NaCL solution and the finite element analysis (FEM) is investigated. Although it takes more than a week in the conventional method, the present method requires one day or so, by employing the same apparatus. In the former research (last year), the analysis of the permeability was based on the one-dimensional exact solution. To take the effect of the specimen geometry, the modification based on the FEM analysis is proposed and plausile permeability coefficients are determined in steel-fiber reinforced concrete. Results show no particular effect of fiber on the permeability, compared with normal concrete.2. The numerical mathods based on the FEM and the boundary element method (BEM) were developed. According to results of the simulation analysis on the diffusion of fission products, it is found that the diffusion effect is limitedly observed near the surface, while the convective effect distributes the products soreadly. Therefore, materials of low permeability are desirable for the barrier.3. On the basis of the state of the art review, the importance of acoustic emission (AE) monitoring is cited. Then, fundamental research on AE waveforem analysis is performed to develop the monitoring device for cracking.