Evaluation Of Structural Integrity And Crack Life Of Shielded Nuclear Main Pump Flywheel

As a part of the passive safety system,the shielded nuclear main pump flywheel belonging to the related components of nuclear safety,subject to supervision of Nuclear Security Agency.Its role is to maintain a certain idle time to expel the core residual heat under the condition of power off,and to prevent the fuel components continued to heat up until burned.Under normal conditions,the flywheel is surrounded by the gap flow field,and there is a large temperature difference between the upper and lower ends of the flywheel,so the working environment is very complicated.In the past research and analysis,the impact of variation of the temperature distribution caused by the gap flow field was often ignored on the structural integrity of the flywheel,this study consider the factor and apply it to the follow-up analysis.Meanwhile,there are initial cracks caused by assembly or machining errors on the surface of the canned main pump flywheel.Under the action of alternating load,it will continue to develop with the increase of the cycle period until the critical,which will lead to the failure of the flywheel and affect the safe operation of the nuclear pump.Therefore,it is necessary to evaluate the life of the flywheel crack.Domestic and foreign scholars tend to simplify the flywheel to semi-infinite structure and combine the semi-empirical formula,or refer to the empirical formula in the ASME Appendix G to calculate the stress intensity factor of the crack,but these two methods do not apply to the bimetallic flywheel with complex structure.This paper establishes a three-dimensional model of canned main pump flywheel with crack and uses the finite element software ASNYS Workbench to analyze the fracture mechanics.Then finds the relationship between the stress intensity factor of flywheel crack with the rotational speed,crack depth and crack length,which is used to fix the formula of stress intensity factor.Moreover,uses the Paris formula to evaluate the life of flywheel crack,which solves the applicability problems in the previous research methods,and has great significance in the safe operation of the nuclear main pump.