Book excerpt: The question of how to effectively, efficiently, and responsibly manage used nuclear fuels is a concern of major impediment in the light of today's increasing usage of nuclear power and development of advanced nuclear reactors. This book focuses on two significant areas of (used) nuclear fuel: the reprocessing technology, and waste disposal and management. The book covers the fundamental knowledge, the current state-of-the-art, and future research activities for each topic. This book provides readers with the fundamental knowledge behind of nuclear used fuel reprocessing and radioactive waste management, and their technical applications, and their requirements and practices; to make the readers aware of social, economic, and environmental concerns as well as technical research needs. The book covers two well-known and well-developed reprocessing technologies: aqueous reprocessing technology, and electrochemical pyroprocessing. On the subject of waste management, it covers the dry storage of used nuclear fuel, novel waste form design, and nuclear waste disposal. This book is a good guide for readers who want to understand, apply, or develop the technologies.