Deep geological isolation of nuclear waste: numerical modeling of repository scale hydrology

Abstract

Problems to be addressed in assessing post-sealing repository performance cover quite a range of physical scales. Some aspects of repository performance such as the effects of the details of room design and waste canister placement must be considered in terms of distances that are small relative to the overall repository dimensions. At the other end of the spectrum, the effects of room, corridor and shaft layout may be assessed initially on the basis of iiry coarse approximations and large distance scales. Typically, the physical processes which dominate various aspects of repository performance are dependent on the distance scales of interest. Although, as will be discussed in the next section, essentially the same processes are active over the whole range of dis tance scales. The relative importance of the processes, the parameter values describing the processes, and the nature of external factors regulating the processes vary considerably from scale to scale. The Hierarchy of Length Scales The repository as a whole is a very complex hydraulic, thermohydraulic, chemical, and thermomechanical system with many different processes active to varying degrees at different scales. Rather than attempting to assess the entire repository performance problem at once or within the framework of a single view of the repository system we suggest that the repository be addressed in terms of three characteristic distance scales. The scales {Figure 1