Longterm performance of structural component of intermediate- and low-level radioactive waste disposal facility

Underground repository for intermediate- and low-level radioactive waste is to be sealed and closed after operation. Structural components, which are generally made of cement concrete, are designed and accommodated in the repository for the purpose of operational convenience and stability after closure. To forecast the change of long-term integrity of the structural components, experimental verification, using in-situ or near in-situ conditions, is necessary. Domestic and foreign requirements with regard to the selection criteria and the performance criteria for structural components in disposal facility were surveyed. Characteristics of various types of cement were studied. Materials and construction methods of structural components similar to those of disposal facility was investigated and test items and methods for integrity of cement concrete were included. Literature survey for domestic groundwater characteristics was performed together with Ca-type bentonite ore which is a potential backfill material. Causes or factors affecting the durability of the cement structures were summarized. Experiments to figure out the ions leaching out from and migrating into cement soaked in distilled water and synthetic groundwater, respectively, were carried out. And finally, diffusion of chloride ion through cement was experimentally measured