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감시시험 결과를 이용한 국내원전 압력용기 재료의 Chemistry Factor 및 RT<sub>PTS</sub> 평가여유도 분석
이호진,윤지현,최권재,이봉상,Lee, Ho-Jin,Yoon, Ji-Hyun,Choi, Kwon-Jae,Lee, Bong-Sang 한국압력기기공학회 2011 한국압력기기공학회 논문집 Vol.7 No.3
The chemistry factor and RTPTS margin for domestic reactor pressure vessel materials were analyzed by using the surveillance data which have been obtained from 8 nuclear power plants in Korea. The surveillance data have been used to assess the integrity of the pressure vessel under the pressurized thermal shock (PTS) event. The chemistry factor, which is determined by the Cu and Ni contents of vessel materials, is considered a proper tool to assess the $RT_{PTS}$. The chemistry factors, which were obtained from the surveillance data of domestic reactor pressure vessels, were investigated and compared with those of Regulatory Guide 1.99 in this study. Regressions for ${\Delta}RT_{NDT}$ were performed to expect the chemistry factor as a function of Cu and Ni, and to estimate $RT_{PTS}$ margin. The margin analysis was performed by comparing the regression graphs and standard deviations with those of Regulatory Guide 1.99. The standard deviations calculated by using the domestic surveillance data for base metal and welds are almost same as the standard deviations which are suggested on Regulatory Guide 1.99, Rev.2.
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문성인,김종민,권준엽,이봉상,최권재,김민철,한상배 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.3
Steam generator (SG) tubes in a nuclear power plant can undergo rapid changes in pressure and temperatureduring an accident; thus, an accurate model to predict short-term creep damage is essential. The theta (q) projection method has been widely used for modeling creep-strain behavior under constantstress. However, many creep test data are obtained under constant load, so creep rupture behavior undera constant load cannot be accurately simulated due to the different stress conditions. This paper proposesa novel methodology to obtain the creep curve under constant stress using a modified q projectionmethod that considers the increase in true stress during creep deformation in a constant-load creep test. The methodology is validated using finite element analysis, and the limitations of the methodology arealso discussed. The paper also proposes a creep-strain model for alloy 690 as an SG material and a novelcreep hardening rule we call the damage-fraction hardening rule. The creep hardening rule is applied toevaluate the creep rupture behavior of SG tubes. The results of this study show its great potential toevaluate the rupture behavior of an SG tube governed by creep deformation.
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Creep strain modeling for alloy 690 SG tube material based on modifi ed theta projection method
문성인,김종민,권준엽,이봉상,최권재,김민철 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.5
During a severe accident, steam generator (SG) tubes undergo rapid changes in the pressure and temperature. Therefore, an appropriate creep model to predict a short term creep damage is essential. In thispaper, a novel creep model for Alloy 690 SG tube material was proposed. It is based on the theta (q)projection method that can represent all three stages of the creep process. The original q projectionmethod poses a limitation owing to its inability to represent experimental creep curves for SG tubematerials for a large strain rate in the tertiary creep region. Therefore, a new modified q projectionmethod is proposed; subsequently, a master curve for Alloy 690 SG material is also proposed to optimizethe creep model parameters, qi (i ¼ 1e5). To adapt the implicit creep scheme to the finite element code, apartial derivative of incremental creep with respect to the stress is necessary. Accordingly, creep modelparameters with a strictly linear relationship with the stress and temperature were proposed. Theeffectiveness of the model was validated using a commercial finite element analysis software. The creepmodel can be applied to evaluate the creep rupture behavior of SG tubes in nuclear power plants
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