EXPERIMENTAL ANALYSIS OF DYNAMIC OPERATIONS OF THE MAIN STEAM RELIEF ISOLATION VALVE USED IN NUCLEAR POWER PLANTS

Main steam relief isolation valve (MSRIV) is one type of advanced control valve used in pressurized water reactors (PWR), such as Hualong One (HPR 1000 in China) and European Pressurized Reactor (EPR). It can provide overpressure protection for the steam generator (SG) and used for waste heat discharging. However, MSRIV may show undesirable operations such as reclose slow under high pressure & temperature conditions (e.g., 8.9 MPa & 316 degrees C) and/or cannot be opened timely under low pressure & temperature conditions (e.g., 0.14 MPa & 316 degrees C). To explore the root causes of these undesirables, an experimental based analysis was specially carried out in this paper. For valve performance measurement, an experimental test rig was developed, thereby not only dynamic responses of the MSRIV under different operating conditions, but also the influence of valve key parameters can be analyzed. The results show that both the system pressure and the throttle area have great influence on the dynamics of the MSRIV. Upon the same disk throttle area, the valve opening time decrease with the inlet pressure, while the valve reclosing time increase with it. For the same inlet pressures, larger throttle area usually led to longer valve opening time and the shorter valve closing time. The results obtained in this study not only provide a reference for the valve early design stage, but also can be used as a criterion for the subsequent numerical modeling works which is of great importance for the flow details acquisition and valve mechanism exploration.