Chapter 12 Radioactive Waste Disposal: Hosting Environment, Engineered Barriers, and Challenges

Radioactive material is being used in many aspects of our life, from medicine to energy generation and to weapon systems. The increasing energy needs and the quest for clean energy makes it very likely that the use of radioactive material will expand in the 21st century together with the need to safely dispose nuclear waste. This chapter provides a brief overview of the issues related to the disposal of radioactive waste, which depending on the material may require isolation from the environment and human populations of tens to hundreds of thousands of years. The basic elements of near-surface disposal facilities used for the disposal of short-lived low-level radioactive waste (SLLW) and intermediate-lived low-level radioactive waste (ILLW) are initially discussed. Subsequently, the chapter concentrates on the various geologic environments and technological solutions used, in several countries, for the disposal of high-level radioactive waste (HLW), providing also the background for the multiple measures taken for the safe disposal of HLW. Particular emphasis is given to the experience of United States and Canada because they represent emplacement in two contrasting geologic environments, the former sitting the repository in the unsaturated, and the latter in the saturated zone. The Canadian experience is discussed in detail as the use of the clay buffer and emplacement in the saturated zone represents an approach that is common to many countries, as a consequence of their difficulty to locate a desert, low precipitation, and remote location, as that of the Yucca Mountain in the United States. Given the need to contain HLW for 1 million years, as mandated in the United States, the chapter also discusses some of the challenges to attempt to make scientific predictions at such time frames and the need to rely on the natural barriers of the hosting environment rather than the engineered barriers