Study On The Structural Integrity Of Bimetallic Flywheel And Containment Of Missiles In The Canned Motor Pump

The reactor coolant pump is important device in the primary loop of the reactor and the main pump flywheel ensures that the pump has sufficient moment of inertia so that the reactor coolant continues to flow through the inertia effect of flywheel when the reactor shutdown urgently or power off.Under certain accident conditions,the main pump may overspeed and the flywheel may break into pieces under centrifugal force,the missiles generated with greater energy will have a significant impact on the pressure-retaining boundary such as motor casing.In severe cases,the LOCA accident is caused by the failure of the first loop pressure boundary.To grasp the influencing rule of the destructive effect on integrity of pressure-retaining boundary imposed by bimetal flywheel missiles in the reactor coolant pump,the similarity criterion number of model flywheel projectile containment test is proposed and the relationship between rotational speed and reduced scale is revealed under the condition of similar model test,and the dimensional problem of model flywheel projectile containment testbed is solved;this paper analyses the impact between tungsten alloy block and pressure-retaining boundary(motor casing)after the failure of the flywheel retaining ring by using LS-DYNA,simulating the process that the boundary contains the flywheel missiles under different conditions(the thickness of motor casing,the number of tungsten alloy blocks,the fragments of retainer).The model test scheme was designed to verify the numerical analysis results and the flywheel of a small reactor main pump is evaluated.The increase in the thickness of motor casing can improve ability of containing the missiles;the retainer fragment has a certain buffering effect on the tungsten alloy block and thus the destructive energy to motor casing is reduced;the more pieces of the retainer broken,the more cushioned the tungsten alloy blocks will be;the more the number of flywheel tungsten alloy blocks,the smaller the damage energy exerted on the pressure boundary by the flying missiles after the flywheel breaks.The results of this study are of great significance to the reliability design of the canned motor pump inert flywheel.