Modeling of Thermohydraulic Processes in a Steam Generator with Several Plugged Heat-Transfer Tubes

Experience with the operation of nuclear power plant (NPP) steam generators (SGs) has shown that the main factor determining the technical condition and actual service life of a steam generator (SG) is the condition of the heat-transfer tubes, which belong to the parts of a steam generator that cannot be replaced or restored. Corrosion defects in heat-transfer tubes initiate and grow during operation of power units. This can lead to depressurization of the primary circuit of the nuclear power plant and primary-to-secondary leakage during on-load operation of the reactor unit. When this leakage in the steam generator exceeds a certain standard value, the power unit is shut down for unscheduled inspection of heat-transfer tubes for integrity. To ensure safe operation of the power unit and to avoid unscheduled shutdown of the reactor unit, the heat-transfer tubes are subjected to nondestructive examination, the results of which are used to plug faulty tubes. This paper presents the results of the development and validation of the thermohydraulic CFD model of the NPP primary circuit in the PGV-1000M steam generator, taking into account the three-dimensional effects in the steam generator headers. To simulate the thermohydraulic processes in heat-transfer tubes of a steam generator heat-transfer tubes in the STAR-CCM + code, a one-dimensional flow and heat-transfer model describing changes in the thermohydraulic parameters of the coolant only along the length of the tubes is implemented in the STAR-CCM+ code. Thermohydraulic calculations of a steam generator with several plugged heat-transfer tubes and the analysis of the effect of their location on the thermohydraulic characteristics of the steam generator under rated operating conditions of the reactor unit have been performed. The results of optional calculations were obtained using the CFD model of the primary SG circuit when varying the number of plugged heat-transfer tubes and their location. The effect of the number of plugged tubes and their location on hydrodynamics and heat transfer in the considered SG has been analyzed.