Development of Methodologies for Predicting and Preventing Vibroacoustic Resonances in VVER NPPs

This paper presents a method for calculating the resonance frequencies of coolant acoustic oscillations. It is shown that the frequencies of coolant acoustic oscillations must be determined both for the nominal operating modes of a nuclear power plant (NPP) and for start-up and emergency operating conditions. The main reasons for which it is necessary to calculate the frequencies of acoustic oscillations are indicated: the relationship between the thermal-hydraulic mode and the neutron-physical characteristics of the reactor; the possibility of vibration-acoustic resonance (VAR) between the oscillations of the working medium and the equipment or individual structural elements, which leads to an unacceptable increase in the vibration level, as well as for the purpose of diagnosing the condition of the equipment and operating parameters of the working medium using acoustic signals. Theoretical prerequisites are presented for physical and mathematical modeling of self-oscillation - acoustic phenomena in such complex systems as the circulation circuit of a NPP with a VVER or the process channel of a nuclear reactor. The main calculation relationships for carrying out engineering calculations of VAR are presented.