Research On Reliability Prediction Method Of AP1000 Reactor Coolant Pump

The reliability of the reactor coolant pump is very important for the safety and reliable operation of nuclear power plant.In the design and development stage of the reactor coolant pump,it is necessary to evaluate the reliability of the reactor coolant pump to ensure the inherent reliability of the reactor coolant pump.Based on the failure rate model proposed in the reliability prediction Manual of American machinery and equipment,this paper presents the failure rate model proposed in the manual,through analyzing its scope of application,studying the principle of its formula and the value of each correction coefficient.The failure rate of the AP1000 reactor coolant pump is predicted by using this model.Meanwhile,the importance and sensitivity of the relevant parameters in the failure rate model of the reactor coolant pump are analyzed,and the main factors affecting the reliability of the reactor coolant pump and its key components are determined.The model provides guidance for the design,manufacture,operation and maintenance of the reactor coolant pump,so as to ensure its high reliability.Firstly,according to the system level logic of the "whole machine-module-parts",the functional structure of AP1000 reactor coolant pump is divided.According to the actual experience of FMEA analysis and engineering technicians,the key components of the reactor coolant pump are screened.The key components of the pump body include pump shafts,water-lubricated radial bearings,impellers and pump casings.The key components of the motor include stator windings,capacitors,thrust bearings,rotor shafts,cans and flywheels.According to the hierarchical division of the reactor coolant pump's functional structure and the selection of key components,the reliability block diagram model of the reactor coolant pump is established by utilizing the relationship between the individual components and the whole system.The failure rate of the reactor coolant pump is the sum of the failure rate of the key parts.In order to predict the failure rate of key components,a basic failure rate is set as benchmark followed by the construction of the correction coefficient based on the failure mode so that each parameter can reflect the impact on the failure rate of components.It is noted that,the focus on the rolling bearing failure rate model in the manual does not apply to the AP1000 reactor coolant pump water lubrication bearing,and the shaft failure rate model lacks relevant correction coefficient,the failure rate model that is not suitable for the cans,and a new model with associated correction coefficient was built.Finally,the research findings suggest that,the mechanical equipment parts failure rate model proposed by the American Mechanical Equipment Reliability Prediction Manual is mostly applicable to the components of the AP1000 reactor coolant pump.The factors affecting the reliability of the AP1000 reactor coolant pump water lubricated bearings are the journal running speed,the bearing load of the bearing bush,the lubricant flow and temperature rise.The upper radial bearing is found to be more susceptible to failure than the lower radial bearing.The main failure modes of the cans are bulging,rupture and burn.The main cause of the bulging during operation is the pressure difference on both sides of the cans.The results of importance analysis and sensitivity analysis show that the parts with relatively great influence on the reliability of AP1000 reactor coolant pump are water-lubricated bearing,cans and motor winding,and the factors that have greater influence are stress concentration of pump shaft,operation temperature of water-lubricated bearing and temperature rise of motor winding.Therefore,in the design and development stage,it is necessary to rationally design the size of the pump shaft rounding to reduce the influence of stress concentration,and at the same time,limit the temperature rise of the reactor coolant pump motor winding within a reasonable range during operation.