Investigation On Transient Behavior Of Reactor Coolant Pump And System

As the key power equipment in the Reactor Coolant System(RCS),the Reactor Coolant Pump(RCP)is an important carrier for the momentum change of the coolant.The internal flow performance and the external characteristics in the hydraulic transient process of the pump are significant in assessing its safety and reliability.At the same time,the performance variation and instability of the system caused by the RCP deserve major concern.The system simulation based on the method of characteristic pays attention to what happens on the whole system scale,whereas neglecting the analysis for the flow fields and flow mechanism of the specific components,which is what the three dimensional CFD simulation specialize in,but it is a difficult thing to accurately determine the boundary conditions in the three dimensional CFD simulation.Therefore,this paper put the reactor coolant pump in the entire system to consider,and coupled one and three dimensional models together to research its transient characteristics.It was noticed that the RCP of CAP1400 is designed welded directly to the Steam Generator(SG)channel head,which makes the flow field in the SG channel head outlet nozzle non-uniform.Simulations were carried out by CFD method through modelling integrally the channel head of SG and RCP.Results show that the head and impeller torque of the pump was reduced due to inflow distortion,and axial loading has dropped slightly whereas radial loading increased significantly.As cavitation occurred,the critical NPSH of the pump increased and anti-cavitation performance was reduced.In order to evaluate the effect of the system on the performance of the RCP furtherly,one dimensional model of the RCS based on FloMASTER was established,which was verified respectively through steady simulation and transient simulation for coast-down process.Also,the process of pump unexpected stopping was analyzed and the backflow and reversal conditions were revealed.The hydraulic and hydrodynamic performance of the RCP during variable flow conditions were analyzed by three dimensional CFD.Results show that H-Q curve and ?-Q curve during the flow decrease process deviated from the steady-state value.The faster the flow reduction process occurred,the smaller the range and degree of the radial force fluctuation under the same flow.In the aspect of 1D-3D coupling simulation,the transfer method of boundary information in the coupling calculation was determined,and a coupling simulation platform was established.Finally,the key parameters affecting the coupling calculation speed rate and stability were analyzed.