Study on transient characteristics of pipeline under centrifugal pump shaft stuck condition

•The reactor coolant pump is one of the core components of the reactor coolant system.•If the reactor coolant pump has a shaft stuck accident, the water hammer phenomenon will cause serious damage to the reactor coolant pump and pipelines.•For this paper, a centrifugal pump closed-loop system is used to replace the reactor coolant system by building a centrifugal pump closed-loop test platform, and three time of 0.5 s, 1 s, and 1.5 s were carried out for the shaft stuck test.•The change of external characteristics of the centrifugal pump during the transition process of shaft stuck is studied.•And through the construction of the test 1:1 three-dimensional water body model, simulate its shaft stuck process, the flow field of the inlet and outlet pipeline changes.•By studying the pressure transient characteristics of the pump inlet and outlet elbows during the shaft stuck transition process, it provides a reference basis for the design of the reactor coolant pump and the safety assessment of the accident. In the pump system, the water hammer effect generated by the shaft stuck accident will cause great harm to the pump and piping system. In order to reveal the transient characteristics of the pipeline during the transition process of vane-pump shaft stuck, three shaft stuck time of Δt = 0.5 s, Δt = 1 s and Δt = 1.5 s is tested by building a closed test bench of centrifugal pump. And establish a 1:1 closed system three-dimensional model to study the external characteristics and internal flow field changes of the pump and piping system during the transition process of the shaft stuck. The study shows that: The rotational speed curves are non-linearly decreasing; the patterns of change in flow rate show a roughly exponential function trending downward; the heads during the shaft stuck will fall rapidly and reach the reverse extreme value. For the pump inlet piping system, the pressure of each place in the speed down to 0 rpm before the peak, the pressure of the outlet pipeline is always down to the reference pressure. Under the same shaft stuck condition, the pressure change in each place of the inlet piping system is basically the same, and the pressure reaches the peak at the same time. The maximum pressure of the inlet and outlet piping is at the rear 3/4 of the elbow. The closer to the face of the inlet and outlet of the elbow, the greater the load force applied; with the elbow as the demarcation, the pressure gradually increases along the flow direction. B