This book presents a critical review of designing, siting, constructing and demonstrating the safety and environmental impact of deep repositories for radioactive wastes. It is structured to provide a broad perspective of this multi-faceted, multi-disciplinary topic: providing enough detail for a non-specialist to understand the fundamental principles involved and with extensive references to sources of more detailed information. Emphasis is very much on 'deep' geological disposal - at least some tens of metres below land surface and, in many cases, many hundred of metres deep. Additionally, only radioactive wastes are considered directly - even though such wastes often contain also significant chemotoxic or otherwise hazardous components. Many of the principles involved are generally applicable to other repository options (e.g. near-surface or on-surface disposal) and, indeed, to other types of hazardous waste. The book presents a current critical review in designing, siting, constructing and demonsrating the safety and environmental impact of deep repositories for radwaste. It addresses the fundamental principles of radioactive waste with up-to-date examples and real-world case studies. It is written for a multi-disciplinary audience, with an appropriate level of detail to allow a non-specialist to understand.