The applicability of a complete and well-qualified plant transient code and model to support in-depth evaluations of anomalous plant transients is shown. Analyses of several operational and abnormal transients that occurred during the first three cycles of the Cofrentes boiling water reactor nuclear power plant are presented. Several safety issues for the Cofrentes and Almaraz power plants are also resolved. These applications demonstrate the need for a very detailed and accurate simulation of the control systems as well as the convenience of having a data acquisition system that is as complete as possible.