A Structural Integrity Evaluation for the Interference-Fit Flywheel of Reactor Coolant Pump

Abstract

In this study, stress analyses and structural integrity evaluations for an interference-fit flywheel assembly of reactor coolant pump are conducted. Finite element stress solutions of the flywheel assembly at the standstill, normal operation speed, design overspeed and joint-release speeds, are obtained. For evaluations of structural integrity of the flywheel with surface cracks, considering ductile and non-ductile fracture, stress intensity factors of a series of surface or edge cracks postulated are also obtained by using the finite element alternating method. In the analyses, release of deformation-controlled stresses caused by structural interactions with centrifugal loads during rotation is considered. Results of stress and fracture evaluations are presented, including the primary and secondary stresses, applied stress intensity factors and the fatigue crack growth rates in the flywheel disc. For the interference-fit flywheel design and material conditions investigated, it is found that fatigue crack growth rates of smaller surface cracks in the flywheel are negligible. The material resistance to non-ductile fracture in terms of material KIC and RTNDT is the governing factor for the structural integrity of the flywheel with larger surface cracks.