Research On The Structural Mechanical Property Of The Multi-ring Flywheel In Reactor Coolant Pump

As an efficient and clean energy,nuclear power has attracted much attention and been widely applied all over the world.However,China’s existing technology still lags behind other countries in the manufacture of nuclear power equipment,especially the design and manufacturing technology of reactor coolant pump(RCP).The RCP is an important part of the prime circuit,known as the heart of nuclear power plant.The flywheel is one of the important components of the RCP.When the main pump system encounters a power shut,the flywheel will provide enough power to prevent nuclear leakage due to high temperature in reactor.Therefore,the design of the RCP flywheel is directly related to the safety of the whole reactor system.The main structure of the RCP flywheel can be classified into the integral structure and the multi-ring structure.At present,the world’s most advanced RCP AP1000 is the multi-ring structure,where the flywheel is divided into three layers,including the inner hub,tungsten alloy and outer hub.The principle of the design has not been published because of the confidentiality of the nuclear power technology.This paper focuses on investigating the design principle of multi-ring flywheel structure by finite element analysis.Firstly,the strength and applicable range of the interference magnitude are analyzed in order to study the structural design of the flywheel.This is also the basis for the following dimension analysis.According to the calculation,the suitable interference magnitude range of the flywheel is 0.7~1.2 mm in the premise of meeting the strength requirements and preventing falling off.Secondly,the design space is severely limited because the RCP flywheel is located in the pressure vessel.The design criterion is to try to put the heavy metal tungsten alloy at the outer edge to increase the moment of inertia.But,if the size of the outer hub is too small,it is hard for the flywheel to meet the strength requirement.Therefore,the size design of the rings of the flywheel is very important in order to maximize the moment of inertia in a limited space.For this situation,the influence of the size distribution of the inner hub,the tungsten alloy and the outer hub of the flywheel on the moment of inertia,distribution of stress and the phenomenon that flywheel occurs off is studied.The reasonable size distribution of flywheel is obtained under the premise to meet the structural strength and to prevent falling off.The result indicates,compared to the same size under the steel material design,the moment of inertia can be increased by 69.1% through the structural designAt last,the mode of vibration of the flywheel with or without prestress is analyzed in order to study the vibration characteristics of flywheel.It is found that the effect of prestress on the flywheel of the modal is not more than 0.5%.At the same time,we also compare the flywheel modal formation of six degrees of freedom of the important participation coefficient.Through comparison,it is found that the vibration modes of the multi-ring flywheel are mainly rotating modes.This thesis studies size distribution and vibration characteristics,which provides reference information for multi-ring structure design of the RCP flywheel.