Reactor internals vibration monitoring of a pressurized water reactor power plant by processing ex-core neutron flux signals

摘要

The vibration of reactor internals including core support barrel and fuel assemblies in a typical pressurized water reactor can be monitored by noise analysis of the ex-core neutron flux signal. Monitoring the neutron noise signals measured by the ex-core power range detectors provides a means for detecting changes in the dominant internals structural conditions or vibration excitations. This paper aims to verify that the reactor internals vibration monitoring system of an optimized power reactor (OPR1000) provides a base for interpreting the significance of changes in the ex-core detector signals with respect to the internal structures and their support conditions. The reactor internals vibration was evaluated by using statistical reactor noise descriptors. Normalized power spectral density, normalized cross-power spectral density, coherence functions and phases were calculated to obtain the beam and shell modes of core support barrel motion by processing signals from twelve ex-core power range neutron detectors located outside of the reactor pressure vessel. The reactor internals vibration monitoring system was well combined with comprehensive analysis and interpretation of the data in accordance with the technical guides, and has been properly operated to detect changes in the condition of the reactor internals.