One of the principal objections to or problems with the use of nuclear fuel is that a proven method for safe disposal of spent nuclear fuel has yet to be established. The central focus of most schemes underway to dispose of these high-level radioactive wastes relies on clay-based buffers and barriers to isolate spent fuel canisters in boreholes deep underground in specially constructed tunnels and caverns. Current thought on the principal methods of containment of high-level radioactive wastes is presented in this book. The authors proceed to discuss the processes and mechanisms involved in the development of long term properties and performance of clay-based buffers and backfills. The procedures and methodologies used to undertake predictions and performance assessments of these materials are also examined.This is an invaluable reference for professionals, researchers, academics and regulators engaged in the development of radioactive waste sites.