Study On Containment Of Missiles And Structural Optimization Of Large Canned Motor Pump Bimetal Flywheel

Nowadays,the third generation nuclear power technology has already become the mainstream technology.In this latest technology,the main reactor coolant pump(RCP)has an enough moment of inertia flywheel.It can drive coolant circulate and provide enough inert flow for primary circuit in order to avoid the reactor core meltdown.Due to the structural characteristics of canned motor pump and the limited installation space of the flywheel,the flywheel design adopts the bimetal structure of the tungsten alloy block to ensure that the flywheel has enough inertia.Therefore,in the normal operation,the safety of the flywheel has a very important impact on the safety of RCP.In this paper,the large canned motor RCP bimetal flywheel is taken as the research object.The structural strength and fracture mechanics of the flywheel are analyzed,and the containment of the pressure-retaining boundary is studied.At last,the structure of bimetal flywheel is optimized.The details are as follows:Using the analytical method,the interference between the bimetal flywheel retaining ring and the tungsten alloy block is solved.When interference value is 1.2mm,the radial stress of inner surface of the retaining ring is 40.98MPa that is compressive stress,and the circumferential stress is 477.516MPa that is tensile stress.By using the finite element method,the interference fit between the bimetal flywheel retaining ring and the tungsten alloy blocks and the contact between the tungsten alloy blocks are considered.When interference value is 1.2mm,the radial stress is 47.9MPa,and the circumferential stress is 513.7MPa.Compared with the results of analytical method,the results of finite element method is more conservative.At the same time,under the imaginary prefabricated crack,the critical speed of the non-ductile fracture of the flywheel is 6600rpm,which is used as the initial velocity of flywheel missile.For the special structure of the bimetal flywheel,the dynamic variation of the kinetic energy and internal energy of the tungsten alloy block and the motor shell during the collision process are analyzed.The influence of different thickness of the motor casing on the collision process is studied,and the critical thickness of the non-containment is 111mm.The influence of different initial velocity on the collision process is studied,and the critical velocity of the non-inclusions event is 480m/s.The influence of different the thickness of tungsten alloy block on the collision process is studied,and the reasonable design range of tungsten alloy thickness is 138mm-143mm.In order to obtain a large moment of inertia and safe structure of the flywheel,this paper aims to the optimization design of CAP1400 that is used in two kinds of bimetal flywheel.The results show:1)For the bimetal flywheel with tungsten alloy blocks,the optimization design of the flywheel retaining ring thickness is 0.029m and the flywheel outer radius is0.458m,which is 0.65%less that the initial design;the moment of inertia is 400.9kgm~2,which is 1.65%higher than the initial design.2)For the bimetal flywheel with tungsten alloy rods,the diameter of the optimized tungsten alloy rod is 82mm and 117mm respectively,and the moment of inertia is 1873.4kgm~2,which is 8.2%higher than the initial design.In this paper,the structural strength and fracture mechanics of bimetal flywheel are analyzed,and the influence of the interference fit and the interaction between tungsten alloy blocks on the whole stress distribution of the flywheel is studied.Based on the analysis of the dynamic process of collision of single tungsten alloy block and motor casing.In the end,the structure of bimetal flywheel is optimized.The research results obtained in this paper have important guiding significance for the design of flywheel system of the large canned motor RCP.