Study On Hydraulic Characteristic Of Reactor Coolant Pump During Startup

AP1000-third generation nuclear power technology reactor coolant pump(RCP)introduced by China is driven by the inverter during its start-up,which was different from other nuclear power technology.In the AP1000 startup process,there is a significant change of the RCP's operating temperature,which will result in fluctuations on the pump parameters.In order to ensure safety of start-up process,the maximum speed of the RCP is limited to 88%of the rated speed,but its setting method has not been reported.Therefore,according to the parameter setting of AP1000 startup process,this paper studied the hydraulic characteristics of self-designed hydraulic model,and deduced the setting method of the maximum limited rotation speed.The pressure fluctuation characteristics of the flow field during the startup of RCP were studied by using the turbulence simulation method.The model was validated by grid independence,and the number of meshes and the quality of mesh were obtained.by using hybrid grid technique.The reliability of the model was verified by the external characteristic test data of the scale model.The flow field statistical analysis showed that with the increase of the operating temperature of RCP,the pressure distribution of the impeller and guide vanes became more uniform and the interference intensity of the impeller and guide vane weakened,and the pressure fluctuation in pressurized water chamber increased.With the increase of rotational speed,the pressure and the local high pressure and low pressure area of impeller outlet increased,and the pressure in pressurized water chamber increased,meanwhile the interference intensity of the impeller and guide was enhanced.The hydrodynamic performance and hydrodynamic performance variation of RCP were studied by the method of theoretical derivation based on similarity law and the model of turbulence simulation.The results showed that the lift and efficiency of RCP were hardly affected by the change of the physical properties during the heating process of the AP1000,while the shaft power and load were greatly affected.Shaft power and axial force with the speed-arising up to the maximum allowed speed reached the first peak,then fell with the temperature arising,and finally with the speed arising to the rated speed reached the second peak point.Therefore,it is necessary to limit the maximum speed during the startup of RCP.The method of setting the maximum limit speed of RCP was deduced considering the load and power safety.According to the existing parameters of AP1000 and numerical calculation results,the method based on load safety was feasible.Thus,the setting of RCP maximum limit speed was obtained in the CAP1000 start process,which could provide the reference for the maximum speed setting of self-design CAP1400 RCP in the startup process.