ABSTRACT
This chapter describes the principles of isolating low-level radioactive waste (LLW) and intermediate-level radioactive waste (ILW) according to two main principles of location: on-ground and underground. Engineered barriers are indispensable, with smectitic clay a major seal component and concrete used for support and providing stable space for placing most types of LLW and ILW. The chapter describes the function of clay barriers with respect to hydraulic and gas conductivities, diffusive transport of solvates, erodibility, and expandability, including summarized techniques for determining them. The main waste-isolating properties are, for clay barriers, minimal permeability, requiring very low hydraulic conductivity, and for concrete, mechanical stability, low permeability, and above all, the ability to provide these potentials without causing degradation of contacting clay or other soil rock and components. The chapter concludes with a description of the release and transport of radionuclides and the definition of safe zones in lee of repositories.
