Evolution of FBR surveillance using a noise analysis and an on-line signal processing

In a fast breeder reactor with a liquid sodium cooling as in the French nuclear type, the main goal of the surveillance and protection systems is to warrant the reactor integrity against every kind of incidents or accidents threatening the reactor, personnel and environment safety. In the future, the surveillance systems could be used to prevent all the events which could lead to an incident. In this way, a large number of neutronic detectors (fission chambers, boron counters), acoustic (sensors with wave guide), thermal (sodium-steel thermocouple) and vibratory sensors have been implemented in and out the primary vessel of these reactors. After a brief presentation of the standard surveillance and protection systems is given, with a recall of the main results obtained in France in the FBR noise analysis range is given. We show the results recently obtained at Phenix and Superphenix in the case of neutronic, thermal, acoustic and vibratory noises. In addition, we present the ALPES system, recently implemented, on line, at SPX with the goal to improve the core thermal surveillance; numeric processing of the thermocouples at the subassembly outlet are used. We show the main results and the improvements in the domain of the local accidents surveillance. Finally, we summarize the possibilities of an on-line noise analysis system for the early detection of FBR abnormalities. (authors)