Benefits of Using Integral Plant Models in Utilities Availability and Safety Issues

Best estimate simulation by means of the thermalhydraulic models of operating nuclear power plants has been impressively helpful for utilities during the last decade. Operation responsibles are today quite used to take advantage of the results of dynamic simulation for their own aims. The final use of these results is somehow specific. The results themselves are depending on codes and models, not only when related to safety issues but also when used to solve availability and operational questions. The paper shows the advantages of using integral plant models, deals with improvements on models and codes, and focus on specially original subjects like control block development. (authors)