Revision with unchanged content. The increasing global concerns about carbon emission and secure energy generation spurred a renewed interest in nuclear energy, alongside with development of advanced nuclear reactor designs and fuel cycles. This book proposes several solutions to improve the cycle of a Light Water Reactor (LWR). It focuses in particular on development of fuel cycles and operational strategies for the International Reactor Innovative and Secure (IRIS), an advanced LWR with integral design developed by an international consortium led by Westinghouse. The solutions proposed combine proven LWR technology with innovative engineering, therefore enabling IRIS, and the larger class of advanced LWRs, to meet aggressive licensing schedule without forgoing key economic and safety requirements for the fuel cycle of an advanced plant. Since the study has been performed through a joint collaboration with the nuclear industry, focus is maintained not only on the quality and innovation of the solutions proposed but also on their effective applicability in the near future. For these reasons, this book will appeal both the researcher and the engineer interested in the future of the nuclear energy.