Structural integrity evaluation for interference-fit flywheels in reactor coolant pumps of nuclear power plants

  • June-soo Park
  • Ha-cheol Song
  • Ki-seok Yoon
  • Taek-sang Choi
  • Jai-hak Park


This study is concerned with structural integrity evaluations for the interference-fit flywheels in reactor coolant pumps (RCPs) of nuclear power plants. Stresses in the flywheel due to the shrinkage loads and centrifugal loads at the RCP normal operation speed, design overspeed and joint-release speed are obtained using the finite element method (FEM), where release of the deformation-controlled stresses as a result of structural interactions during rotation is considered. Fracture mechanics evaluations for a series of cracks assumed to exist in the flywheel are conducted, considering ductile (fatigue) and non-ductile fracture, and stress intensity factors are obtained for the cracks using the finite element alternating method (FEAM). From analysis results, it is found that fatigue crack growth rates calculated are negligible for smaller cracks. Meanwhile, the material resistance to non-ductile fracture in terms of the critical stress intensity factor(K IC) and the nil-ductility transition reference temperature RTinNDT are governing factors for larger cracks.

Key Words

Structural Integrity Interference-Fit Flywheel Residual Stress Reactor Coolant Pum 



Inner radius of flywheel disc [mm]


Outer radius of flywheel disc [mm]


Scaling constant


Ratio of half length (c)-to-depth (a) of elliptical crack


Fatigue crack growth per load cycle


Elastic modulus of material [KN/mm2]


Stress intensity factor of crack


Mode I stress intensity factor of crack


Slope of log (da/dN) vs. log (ΔAKl) curve


Primary stress intensity [N/mm2]


Primary bending stress intensity [N/mm2]


Primary membrane stress intensity [N/mm2]


Secondary stress intensity [N/mm2]


Cyclic load ratio ofKmm to kmax


Radial distance in flywheel disc [mm]


Mean radius of flywheel disc, (a+b)/2 [mm]


Scaling parameter


Design stress intensity value [N/mm2]


Distance in the meridional direction along the thickness of flywheel [mm]


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Copyright information

© The Korean Society of Mechanical Engineers (KSME) 2005

Authors and Affiliations

  • June-soo Park
    • 1
  • Ha-cheol Song
    • 1
  • Ki-seok Yoon
    • 1
  • Taek-sang Choi
    • 1
  • Jai-hak Park
    • 2
  1. 1.Mechanical System Engineering Dept.Korea Power Engineering Company, Inc.Yuseong-guKorea
  2. 2.Safety Engineering Dept, College of EngineeringChungbuk National UniversityCheongjuKorea

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