Knowledge of the tectonic setting of the site for a nuclear facility is required in order to develop a design for the facility and to evaluate its safety, both during its operational phase and, in the case of a radioactive waste repository, following its closure. Understanding the tectonic evolution of the site and of the area in which it lies permits estimation of, for example, future seismic or volcanic activity. In this chapter, we focus specifically on the investigation of sites proposed for deep geological repositories for radioactive waste, although the structured approach and many of the general principles discussed are more widely applicable to the siting of other nuclear facilities. This chapter also focuses on the situation of a relatively stable tectonic environment, which exists in much of Scandinavia, where volcanic activity is not a consideration and where the maximum level of seismic activity is low, at least as far into the future as the next glaciation. Olkiluoto, in Finland, is used as an example of such a stable tectonic environment to illustrate the approach that is being taken in its characterization. Neotectonic activity is still of interest, however, in a Scandinavian context, and reference is also made to the situation of sites in less tectonically stable environments.

An understanding of the tectonic setting of a site, even where the tectonic activity is relatively benign, is an integral part of developing an understanding of the overall geological environment, so that a convincing and well-founded geological model of the site can be developed.