Influence of Self-Oscillations in VVER Coolant on Failures Fuel and Control and Protection Systems

The problem of ensuring the reliability of fuel assemblies (FA) and drives of control and protection systems (CPS) is relevant for the nuclear power plants (NPP) with water-water power reactors (VVER). The main cause of FA damage is fretting corrosion. The occurrence of vibroacoustic resonance (VAR) accelerates the wear of fuel rod (FR) shell. The methods and calculating results of frequencies of acoustic standing waves (ASW) in a reactor installation (RI) are presented. It is established that self-generation of ASW with frequencies from 150 to 300 Hz occurs in a vortex chamber located between the perforated part of the core barrel and the outlet of pipelines of hot threads. The use of the developed methods and algorithms for ASW calculating allows to construct the acoustic fields of RI and the steam generator for any design thermo hydraulically parameters of the coolant, and identify the conditions for the occurrence of VAR with the FA and with the drive case of the stepper electro mechanism (SHEM-3) CPS.