NPP main feedwater flow Venturi tube erosion characteristics study and improvement

The main feedwater flow of nuclear power units is mainly measured according to Venturi tube differential pressure measurement philosophy. However Venturi tube is subject to fluid erosion and its characteristics will change, directly affecting the measurement accuracy of main feedwater flow which is an important process parameter for nuclear power units. It analyzes the fluid erosion phenomenon of NPP Venturi tubes based on the main feedwater flow measurement data and operation experience of several nuclear power units in many years, and gives erosion characteristic formulas and erosion characteristic curves. In addition, this paper provides improvement solutions in the aspects of differential pressure correction, replacement criteria establishment, design improvement (in selection of high erosion resistance material for internal passage and improvement of construction strength of weak parts) and real-time monitoring of flow data during power operation. These solutions have been verified on site and found feasible and effective.