Nuclear Engineering and Technology

Korean Nuclear Society (한국원자력학회)
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Proposal of the Penalty Factor Equations Considering Weld Strength Over-Match

  • Kim, Jong-Sung (Department of Nuclear Engineering, Sejong University) ;
  • Jeong, Jae-Wook (Korea Hydro & Nuclear Power Co., Ltd.) ;
  • Lee, Kang-Yong (State Key Laboratory of Structural Analysis for Industrial Equipment, Department of Engineering Mechanics, Dalian University of Technology)
  • Received : 2016.08.02
  • Accepted : 2017.01.05
  • Published : 2017.08.25
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Abstract

This paper proposes penalty factor equations that take into consideration the weld strength over-match given in the classified form similar to the revised equations presented in the Code Case N-779 via cyclic elastic-plastic finite element analysis. It was found that the $K_e$ analysis data reflecting elastic follow-up can be consolidated by normalizing the primary-plus-secondary stress intensity ranges excluding the nonlinear thermal stress intensity component, $S_n$ to over-match degree of yield strength, $M_F$. For the effect of over-match on $K_n{\times}K_{\nu}$, dispersion of the $K_n{\times}K_{\nu}$ analysis data can be sharply reduced by dividing total stress intensity range, excluding local thermal stresses, $S_{p-lt}$ by $M_F$. Finally, the proposed equations were applied to the weld between the safe end and the piping of a pressurizer surge nozzle in pressurized water reactors in order to calculate a cumulative usage factor. The cumulative usage factor was then compared with those derived by the previous $K_e$ factor equations. The result shows that application of the proposed equations can significantly reduce conservatism of fatigue assessment using the previous $K_e$ factor equations.

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References

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