The opening of energy markets is leading to increased competition, and the nuclear power industry must adapt if it is to meet this challenge. Internationally discussions are taking place among government authorities and electric utilities and vendors on how to deal with the rapid technical development and optimisation of nuclear fuel and its utilisation under new, more aggressive fuel management strategies. Improving reactor core monitoring systems is an important part of this process. Participants in a recent NEA workshop discussed how instrumentation, methods and models used in core monitoring can be validated or, if needed, improved and further developed to provide more reliable and detailed information on local power in the core and on other parameters indirectly affecting fuel duty. This book shows how the core monitoring system can be used to support reactor operation in normal and anticipated transient modes and to supply data used to derive initial key core parameters for transient and accident analysis.