The Diapason system is designed to aid the supervision of continuous processes that evolve with slow dynamics, such as those used for reprocessing nuclear fuels. The system gives operators a synthetic image of the process, thanks to modeling inspired by qualitative physics and process control theory. By following the evolution of relevant variables, whether measurable or not, and giving associated explanations, it can predict the evolution of processes, thus enabling management by anticipation. IT also detects and promptly analyzes incidental situations, thus performing preventive maintenance and managing degraded conditions. Finally, one it diagnoses defects based on model/process comparisons, it feeds those results to the module that diagnoses faults using structural knowledge of the process.