Papers by Author: Han Sub Chung

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Authors: Sung Ho Lee, Han Sub Chung, Tae Ryong Kim, Su Cheol Jeon
2204
Authors: Jae Bong Lee, Jai Hak Park, Sung Ho Lee, Hong Deok Kim, Han Sub Chung
239
Authors: Hyun Su Kim, Tae Eun Jin, Hong Deok Kim, Han Sub Chung, Yoon Suk Chang, Young Jin Kim
Abstract: Steam generator in a nuclear power plant is huge heat exchanger that transfers heat from reactor to make steam to drive turbine-generator. Failure of the steam generator tubes can result in the release of fission products to the secondary side. Therefore, accurate integrity assessment of the cracked steam generator tubes is of great importance for maintaining the safety of the nuclear power plant. This paper provides limit loads for circumferential through-wall cracks in steam generator tubes under combined internal pressure and bending loads. Such limit loads are developed on the basis of three dimensional finite element analyses assuming elastic-perfectly plastic material behavior. As for the crack location, both the top of the tubesheet and U-bend regions are considered. The analysis results can be directly applied to the practical integrity assessment of cracked steam generator tubes, because the comparison between experimental data and FE results shows a very good agreement.
1357
Authors: Hyun Su Kim, Jong Sung Kim, Tae Eun Jin, Hong Deok Kim, Han Sub Chung
1240
Authors: Ouk Sub Lee, Hyun Su Kim, Jong Sung Kim, Tae Eun Jin, Hong Deok Kim, Han Sub Chung
Abstract: Operating experience of steam generators has shown that cracks of various morphologies frequently occur in the steam generator tubes. These cracked tubes can stay in service if it is proved that the tubes have sufficient safety margin to preclude the risk of burst and leak. Therefore, integrity assessment using exact limit load solutions is very important for safe operation of the steam generators. This paper provides global and local limit load solutions for surface cracks in the steam generator tubes. Such solutions are developed based on three-dimensional (3-D) finite element analyses assuming elastic-perfectly plastic material behavior. For the crack location, both axial and circumferential surface cracks, and for each case, both external and internal cracks are considered. The resulting global and local limit load solutions are given in polynomial forms, and thus can be simply used in practical integrity assessment of the steam generator tubes, because the comparison between experimental data and FE solutions shows good agreement.
1704
Authors: Jae Bong Lee, Jai Hak Park, Hong Deok Kim, Han Sub Chung, Tae Ryong Kim
Abstract: A statistical assessment model for structural integrity of steam generator tubes with axial cracks at the top of the tubesheet was proposed using Monte Carlo method. In the model, a method for estimating the number of "real cracks" from in-situ inspection (ISI) data was used. Based on the estimated "real cracks", the number of newly detected cracks and growth of cracks during arbitrary operating period were simulated using the Monte Carlo method. The flaw growth rate used in the simulation was statistically calculated from the periodic in-service non-destructive inspection data. The number of cracks, the probabilistic distribution of crack sizes at the end of next operating interval and the probability of burst during operation were calculated from numerously repeated simulations using the proposed model.
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