The theoretical modeling and monitoring of WWER fuel assembly vibrations under operating conditions

A configuration of a fuel assembly (FA) vibration monitoring system is proposed in the paper. The vibration monitoring of the fuel assembly (FA) is the main experimental support during the processes of FA design, FA commissioning and FA commercial operation. Such monitoring is addressed to define the limits for hydrodynamic loadings of the FA and to estimate the characteristics of FA dynamic response. The last should include the estimation of vibration both FA and internal as a whole, because the oscillations of the FA and internals have interdependent nature and in many respects are determined by an actual conditions of support structures. The paper also presents a flow chart of the FA vibration analysis including internal relations and feedbacks as well as a configuration of FA vibration monitoring system. The necessity of the theoretical modeling of fuel vibration characteristics is discussed and used for interpretation of the monitoring results related to the probable abnormal vibrational conditions. Some results of vibration-noise measurements of WWER-440 fuel assemblies as an example of vibration monitoring system application are also given in this work