Fundamental Study of the Geological Disposal of High-Level Nuclear Waste

点击翻译按钮获取中文摘要

The multi-barrier concept now forms the backbone of geological disposal programs in most countries. The manufactured components of the multi-barrier system constitute an engineered barrier system(E.B.S). The EBS design is constrained by the deep geological environment where the repository is constructed. In such an environment, groundwater is reducing and fluxes are small. The engineered barrier system consists of the vitriaed waste, overpack and buffer material. The buffer material is selected to have a very low permeability, so that effectively no advective flow occurs in the EBS.However, the construction, operation and closure activities will be carried out with a minimum disturbance to the geological environment in surrounding host rock. It is important to grasp the geological environment accurately during and after the construction. Micromechanics-based continuum(MBC)theory proposed by authors can reflect the effects of density, orientation and connectivity of joints as well as the property of the joints. In this study, the MBC analysis is employed to analyze the excavation of disposal tunnel and the change of the environment around the tunnel is discussed with paying attention to joints in a rock mass through the analyses.From the numerical results, it is concluded that(1)The mechanical behavior of the rock mass is strongly affected by the direction of initial stresses, the joint density, and their combinations.(2)The shape or size of the disposal tunnel has an impact on the joint deformation.(3)These results lead that the excavation of a tunnel changes the geological environment such as permeability.(4)The numerical results before the construction of disposal institution of high-level radioactive waste give us the approximate changes of environmental properties in the institution after the excavation of caverns and tunnels.