• Title, Summary, Keyword: P-T Limit Curve

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Evaluation of Pressure-Temperature Limit Curve for the Safe Operation of an RFV based on 3-D Finite Element Analyses (유한요소해석을 이용한 원자로용기 압력-온도 한계곡선의 평가)

  • Lee, Taek-Jin;Park, Yun-Won;Lee, Jin-Ho;Choe, Jae-Bung;Kim, Yeong-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.10
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    • pp.1567-1574
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    • 2001
  • In order to operate an RPV safely it is necessary to keep the pressure-temperature (P-T) limit during the heatup and cooldown process. While the ASME Code provides the P-T limit curve for safe operation, this limit curve has been prepared under conservative assumptions In this paper the effects of conservative assumptions involved in the P-T limit curve specified in the ASME Code Sec. XI were investigated. Three different parameters the crack depth the cladding thickness and the cooling rate, were reviewed based on 3-D finite element analyses. Also the constraint effect on P-T limit curve generation was investigated based on J- T approach. It was shown that the crack depth and the constraint effect change the safe region in P-T limit curve significantly Therefore it is recommended to prepare a more precise P-T limit curve based on finite element analysis to obtain P-T limit for safe operation of an RPV.

Construction of the P-T Limit Curve for the Nuclear Reactor Pressure Vessel Using Influence Coefficient Methods : Cooldown Curve (영향계수를 이용한 원자로 압력용기의 운전제한곡선 작성 : 냉각곡선)

  • Jang, Chang-Hui
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.3
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    • pp.505-513
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    • 2002
  • During heatup and cooldown of pressurized water reactor, thermal stress was generated in the reactor pressure vessel (RPV) because of the temperature gradient. To prevent potential failure of RPV, pressure was required to be maintained below the P-T limit curves. In this paper, several methods for constructing the P-T limit curves including the ASME Sec. XI, App. G method were explained and the results were compared. Then, the effects of the various parameters such as flaw size, flaw orientation, cooldown rate, existence of chad, and reference fracture toughness, were evaluated. It was found that the current ASME Sec. XI App. G method resulted in the most conservative P-T limit curve. As the more accurate fracture mechanics analysis results were used, some of the conservatism can be removed. Among the parameters analysed, reference flaw orientation and reference fracture toughness curve had the greatest effect on the resulting P-T limit curves.

Comparative Study of P-T Limit Curves between 1998 ASME and 2017 ASME Code Applied to Typical OPR1000 Reactors

  • Maragia, Joswhite Ondabu;Namgung, Ihn
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.15 no.2
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    • pp.1-8
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    • 2019
  • The integrity of the Reactor Pressure Vessel (RPV) is affected by the neutrons bombarding the vessel wall leading to embrittlement. This irradiation-induced embrittlement leads to reduction in the fracture toughness of RPV materials. This paper presents a comparative study of typical Optimized Power Reactor (OPR)1000 reactor pressure-temperature (P-T) limit curves using the pre-2006 American Society of Mechanical Engineers (ASME) editions used in the power plant and the current ASME edition of 2010. The current ASME Code utilizes critical reference stress intensity factor based on the lower bound of static, while the Pre-2006 ASME editions are based the critical reference stress intensity factor based on the lower bound of static, dynamic and crack arrest. Model-Based Systems Engineering approach was used to evaluate ASME Code Section XI Appendix G for generating the P-T limit curves. The results obtained from this analysis indicate decrease in conservatism in P-T limit curves constructed using the current 2017 ASME code, which can potentially increase operational flexibility and plant safety. Hence it is recommended to use ASME code edition after 2006 be used in all operating nuclear power plants (NPPs) to establish P-T limit curve.

Pressure-temperature limit curve for reactor vessel evaluated by ASME code

  • Jhung, Myung Jo;Kim, Seok Hun;Jung, Sung Gyu
    • Structural Engineering and Mechanics
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    • v.14 no.2
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    • pp.191-208
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    • 2002
  • A comparative assessment study for a generation of the pressure-temperature (P-T) limit curve of a reactor vessel is performed in accordance with ASME code. Using cooling or heating rate and vessel material properties, stress distribution is obtained to calculate stress intensity factors, which are compared with the material fracture toughness to determine the relations between operating pressure and temperature during reactor cool-down and heat-up. P-T limit curves are analyzed with respect to defect orientation, clad thickness, toughness curve, cooling or heating rate and neutron fluence. The resulting P-T curves are compared each other.

Evaluation of RPV according to alternative fracture toughness requirements

  • Lee, Sin-Ae;Lee, Sang-Hwan;Chang, Yoon-Suk
    • Structural Engineering and Mechanics
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    • v.53 no.6
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    • pp.1271-1286
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    • 2015
  • Recently, US NRC revised fracture toughness requirements as 10CFR50.61a to reduce the conservatism of 10CFR50.61. However, unlike previous studies relating to the initial regulation, structural integrity evaluations based on the alternative regulation are not sufficient. In the present study, PTS and P-T limit curve evaluations were carried out by using both regulations and resulting data were compared. With regard to the PTS evaluation, the results obtained from the alternative requirements were satisfied with the criterion whereas those obtained from the initial requirements did not meet the criterion. Also, with regard to the P-T limit curve evaluation, operating margin by 10CFR50.61a was greater than that by 10CFR50.61.

Comparison of Fatigue Strength Criteria for TiNi/Al6061-T6 and TiNi/Al2024-T4 Shape Memory Alloy Composite (TiNi/Al6061-T6과 TiNi/Al2024-T4 형상기억복합재료에 대한 피로강도기준의 비교)

  • Jo, Young-Jik;Park, Young-Chul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.2
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    • pp.99-107
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    • 2009
  • This study produced a design curve and fatigue limit for a variation in volume ratio and reduction ratio of TiNi/Al composites. In many cases, stress-life curve does not indicate fatigue limit, so it was presented by probabilistic-stress-life curve. Goodman diagram was used to analyze the fatigue strength of materials with a finite life determined by repeated load and the fatigue strength of endurance limit with an infinite life. The fatigue experiment was conducted using the scenk-type plane bending specimen in same shape. The result of the fatigue test, which had been conducted under consistent stress amplitude, was examined. (i) The optimal condition for TiNi/Al in accordance with hot pressing (ii) Impacts of fatigue limit caused by a variation in reduction ratio and volume ratio of TiNi/Al composites (iii) Probability distribution for fatigue limit of TiNi/Al2024 and TiNi/Al6061.

Development of a RVIES Syetem for Reactor Vessel Integrity Evaluation (원자로용기 건전성평가를 위한 RVIES 시스템의 개발)

  • Lee, Taek-Jin;Choe, Jae-Bung;Kim, Yeong-Jin;Park, Yun-Won;Jeong, Myeong-Jo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.8
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    • pp.2083-2090
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    • 2000
  • In order to manage nuclear power plants safely and cost effectively, it is necessary to develop integrity evaluation methodologies for the main components. Recently, the integrity evaluation techniques were broadly studied regarding the license renewal of nuclear power plants which were approaching their design lives. Since the integrity evaluation process requires special knowledges and complicated calculation procedures, it has been allowed only to experts in the specified area. In this paper, an integrity evaluation system for reactor pressure vessel was developed. RVIES(Reactor Vessel Integrity Evaluation System) provides four specific integrity evaluation procedures covering PTS(Pressurized Thermal Shock) analysis, P-T(Pressure-Temperature) limit curve generation, USE(Upper Shelf Energy) analysis and Fatigue analysis. Each module was verified by comparing with published results.

The Effects of Decompression Therapy by Fixed Pelvic System on Low Back Pain During Pregnancy (골반고정장치에 의한 감압치료가 임산부 요통환자의 통증, 일상생활 제한 및 요추만곡에 미 치는 영향에 관한 연구)

  • Kim, Hee-Ra;Kim, Yoon-Shin;Kim, Seong-Ho;Kim, Myung-Joon
    • Journal of Korean Physical Therapy Science
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    • v.15 no.1
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    • pp.1-9
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    • 2008
  • Background and Purpose : This study serves the purpose to present the effective way on back pain therapy for women during their pregnancy by comparing and analyzing the effects influencing on pain index, limits on daily life, and diminution of lumbar curve, when having treated for 6 weeks, dividing into therapy group, applied by decompression therapy on spine without unnecessary effects on the pregnant women and their fetus and the existent general physiotherapy group, applied on diminution of their back pain. Subject & methods : We made impregnate women of 30(25${\sim}$34years), as the subject of this study, who understood, and agreed with, this study, among pregnant women who were diagnosed as back pain. Pain intensity, limit index on daily life, and lumbar curve test, prior to experiment was implemented as paired t-test, comparison of the difference of average by each group before and after experiment was analysed as independent t-test, and statistical examination level was set up as 0.05. Results : The difference of average of pain and limit on daily life between the group, SDTG(spinal decompression therapy group), and the group, GPTG(general physical therapy group), before and after experiment was diminished as much as 44.4% and 16.79% each after completed 6 weeks' experiment, limit on daily life in both groups showed as much as 37.2% and 21.5% each, in the end, they statistically showed conspicuous difference(p<.05). Comparison of lumbar curves between both groups, SDTG and GPTG, before and after experiment, were diminished from -23.13${\pm}$4.85 to -15.66${\pm}$3.71, and there was no remarkable difference(p<.05). Conclusion : As, in this study, decompression therapy is more effective than general physical therapy with pregnancy low back pain in pain, limitation of daily life, lumbar curve.

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