• Title, Summary, Keyword: 관막음 기준

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Study on Plugging Criteria for Thru-wall Axial Crack in Roll Transition Zone of Steam Generator Tube (증기발생기 전열관 확관천이부위 축방향 관통균열의 관막음 기준에 관한 연구)

  • Park, Myeong-Gyu;Kim, Yeong-Jong;Jeon, Jang-Hwan;Kim, Jong-Min;Park, Jun-Su
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.9
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    • pp.2894-2900
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    • 1996
  • The stream generator tubes represent an integral part of a major barrier against the fission product release to the environment. So, the rupture of these tubes could permit flow of reactor coolant into the secondary system and injure the safety of reactor coolant system. Therefore, if the crack was detected during In-Service Inspection of tubes the cracked tube should be evaluated by the pulgging criteria and plugged or not. In this study, the fracture mechanics evaluation is carried out on the thru-wall axial crack due to Primary Water Stress Corrosion Cracking in the roll transition aone of steam generator tube to help the assurence the integrity of tubes and estabilish the plugging criteria. Due to the Inconel which is used as tube material is more ductile than others, the plastic instability repture theory was used to calculate the critical and allowable crack length. Based on Leak Before Break concept the leak rate for the critical crack length and the allowable leak rate are compared and the safety of tubes was given.

Tube Plugging Criteria for the Non-Regenerative Heat Exchanger in the Steam Generator Blowdown System of Nuclear Power Plant (증기발생기 취출수계통 비재생열교환기 전열관 관막음 기준 설정)

  • Kim, Hyeong-Nam;Choe, Seong-Nam;Yu, Hyeon-Ju;Choe, Jin-Hyeok
    • Proceedings of the KWS Conference
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    • pp.38-40
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    • 2006
  • Nuclear power plants are urged to reduce operating and maintaining costs to remain competitive as well as to increase the safety preventing the radioactive material to the atmosphere. To reduce the cost and to increase the safety, the inspection of balance-of-plant heat exchanger becomes important. However, there are some problems for plugging the heat exchanger tubes since the criterion and its basis are not clearly described. The codes and standards related to show the tube plugging criteria may not exist currently. In this paper, a method to establish the tube plugging criteria of BOP heat exchangers is introduced and the tube plugging criteria for the non-regenerative heat exchanger in the steam generator blow-down system of nuclear power plant. This method relies on the similar method used to establish the plugging criteria for the steam generator tubes.

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Optimum Failure Prediction Model of Steam Generator Tube with Two Parallel Axial Through-Wall Cracks (두개의 평행한 축방향 관통균열이 존재하는 증기발생기 세관의 최적 파손예측모델)

  • Lee, Jin-Ho;Song, Myung-Ho;Choi, Young-Hwan;Kim, Nak-Cheol;Moon, Seong-In;Kim, Young-Jin
    • Proceedings of the KSME Conference
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    • pp.1186-1191
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    • 2003
  • The 40% of wall criterion, which is generally used for the plugging of steam generator tubes, may be applied only to a single crack. In the previous study, a total of 9 failure models were introduced to estimate the local failure of the ligament between cracks and the optimum coalescence model of multiple collinear cracks was determined among these models. It is, however, known that parallel axial cracks are more frequently detected during an in-service inspection than collinear axial cracks. The objective of this study is to determine the plastic collapse model which can be applied to the steam generator tube containing two parallel axial through-wall cracks. Nine previously proposed local failure models were selected as the candidates. Subsequently interaction effects between two adjacent cracks were evaluated to screen them. Plastic collapse tests for the plate with two parallel through-wall cracks and finite element analyses were performed for the determination of the optimum plastic collapse model. By comparing the test results with the prediction results obtained from the candidate models, a plastic zone contact model was selected as an optimum model.

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Structural Integrity Evaluation of SG Tube with Surface Wear-type Defects (표면 마모결함을 고려한 증기발생기 세관의 구조건전성 평가)

  • Kim, Jong-Min;Huh, Nam-Su;Chang, Yoon-Suk;Hwang, Seong-Sik;Kim, Joung-Soo;Kim, Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.12
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    • pp.1618-1625
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    • 2006
  • During the last two decades, several guidelines have been developed and used for assessing the integrity of a defective steam generator (SG) tube that is generally caused by stress corrosion cracking or wall-thinning phenomenon. However, as some of SG tubes are also failed due to fretting and so on, alternative failure estimation schemes are required for relevant defects. In this paper, parametric three-dimensional finite element (FE) analyses are carried out under internal pressure condition to simulate the failure behavior of SG tubes with different defect configurations; elliptical wear, tapered and flat wear type defects. Maximum pressures based on material strengths are obtained from more than a hundred FE results to predict the failure of SG tube. After investigating the effect of key parameters such as defect depth, defect length and wrap angle, simplified failure estimation equations are proposed in relation to the equivalent stress at the deepest point in wear region. Comparison of failure pressures predicted by the proposed estimation scheme with corresponding burst test data showed a good agreement.

Assessment of Steam Generator Tubes with Multiple Axial Through-Wall Cracks (축방향 다중관통균열이 존재하는 증기발생기 세관 평가법)

  • Moon, Seong-In;Chang, Yoon-Suk;Kim, Young-Jin;Lee, Jin-Ho;Song, Myung-Ho;Choi, Young-Hwan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.11
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    • pp.1741-1751
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    • 2004
  • It is commonly requested that the steam generator tubes wall-thinned in excess of 40% should be plugged. However, the plugging criterion is known to be too conservative for some locations and types of defects and its application is limited to a single crack in spite of the fact that the occurrence of multiple through-wall cracks is more common in general. The objective of this research is to propose the optimum failure prediction models for two adjacent through-wall cracks in steam generator tubes. The conservatism of the present plugging criteria was reviewed using the existing failure prediction models for a single crack, and six new failure prediction models for multiple through-wall cracks have been introduced. Then, in order to determine the optimum ones among these new local or global failure prediction models, a series of plastic collapse tests and corresponding finite element analyses for two adjacent through-wall cracks in thin plate were carried out. Thereby, the reaction force model, plastic zone contact model and COD (Crack-Opening Displacement) base model were selected as the optimum ones for assessment of steam generator tubes with multiple through-wall cracks. The selected optimum failure prediction models, finally, were used to estimate the coalescence pressure of two adjacent through-wall cracks in steam generator tubes.

Evaluation of Plastic Collapse Behavior for Multiple Cracked Structures (다중균열 구조물의 소성붕괴거동 평가)

  • Moon, Seong-In;Chang, Yoon-Suk;Kim, Young-Jin;Lee, Jin-Ho;Song, Myung-Ho;Choi, Young-Hwan;Hwang, Seong-Sik
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.11
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    • pp.1813-1821
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    • 2004
  • Until now, the 40% of wall thickness criterion, which is generally used for the plugging of steam generator tubes, has been applied only to a single cracked geometry. In the previous study by the authors, a total number of 9 local failure prediction models were introduced to estimate the coalescence load of two collinear through-wall cracks and, then, the reaction force model and plastic zone contact model were selected as the optimum ones. The objective of this study is to estimate the coalescence load of two collinear through-wall cracks in steam generator tube by using the optimum local failure prediction models. In order to investigate the applicability of the optimum local failure prediction models, a series of plastic collapse tests and corresponding finite element analyses for two collinear through-wall cracks in steam generator tube were carried out. Thereby, the applicability of the optimum local failure prediction models was verified and, finally, a coalescence evaluation diagram which can be used to determine whether the adjacent cracks detected by NDE coalesce or not has been developed.