• Title/Summary/Keyword: Pressure Tubes

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Numerical and analytical predictions of nuclear steam generator secondary side flow field during blowdown due to a feedwater line break

  • Jo, Jong Chull;Jeong, Jae-Jun;Moody, Frederick J.
    • Nuclear Engineering and Technology
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    • v.53 no.3
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    • pp.1029-1040
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    • 2021
  • For the structural integrity evaluation of pressurized water reactor (PWR) steam generator (SG) tubes subjected to transient hydraulic loading, determination of the tube-to-tube gap velocity and static pressure distributions along the tubes is prerequisite. This paper addresses both computational fluid dynamics (CFD) and analytical approaches for predicting the tube-to-tube gap velocity and static pressure distributions during blowdown following a feedwater line break (FWLB) accident at a PWR SG. First of all, a comparative study on CFD calculations of the transient velocity and pressure distributions in the SG secondary sides for two different models having 30 or no tubes is performed. The result shows that the velocities of sub-cooled water flowing between any adjacent two tubes of a tubed SG model during blowdown can be roughly estimated by applying the specified SG secondary side porosity to those of the no-tubed SG model. Secondly, simplified analytical approximate solutions for the steady two-dimensional SG secondary flow velocity and pressure distributions under a given discharge flowrate are derived using a line sink model. The simplified analytical solutions are validated by comparing them to the CFD calculations.

Formation and Growth Estimation of Blister in Zr-2.5Nb Pressure Tubes based on Finite Element Analysis (유한요소해석을 이용한 지르코늄 압력관의 블리스터 생성 및 성장 해석)

  • Huh, Nam-Su;Kim, Yun-Jae;Kim, Young-Jin;Kim, Young-Seok;Cheong, Yong-Moo
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1133-1138
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    • 2003
  • The pressure tubes, which contain high temperature heavy water and fuel, are within the core of a CANDU nuclear reactor, and are thus subjected to high stresses, temperature gradient, and neutron flux. Further, it is well known that pressure tubes of cold-worked Zr-2.5Nb materials result in hydrogen diffusion, which create fully-hydrided regions (frequently called Blister). Thus a proper investigation of hydrogen diffusion within zirconium-alloy nuclear components, such as CANDU pressure tube and fuel channels is essential to predict the structural integrity of these components. In this respect, this paper presents numerical investigation of hydrogen diffusion to quantify the hydrogen concentration for blister growth of CANDU pressure tube. For this purpose, coupled temperature-hydrogen diffusion analyses are performed by means of two-dimensional finite element analysis. Comparison of predicted temperature field and blister with published test data shows good agreement.

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Vibration Characteristics of Steam Generator U-tubes with Defect (결함을 가진 증기발생기 U-튜브의 진동특성)

  • 조종철;정명조;김웅식;김효정;김태형
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.13 no.5
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    • pp.400-408
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    • 2003
  • This paper investigates the vibration characteristics of steam generator (SG) U-tubes with defect. The operating SG shell-side flow field conditions for determining the fluidelastic instability parameters such as added mass are obtained from three-dimensional SG flow calculation. Modal analyses are performed for the U-tubes either with axial or circumferential flaw with different sizes. Special emphases are on the effects of flaw orientation and size on the modal and instability characteristics of tubes, which are expressed in terms of the natural frequency, corresponding mode shape and stability ratio. Also, addressed is the effect of the internal pressure on the vibration characteristics of the tube.

Root Cause Analysis of Axial ODSCC of Steam Generators Tubes of OPR1000 (한국표준형 원전 증기발생기 전열관 축방향 ODSCC 발생원인 분석)

  • Kim, Hong-deok;Park, Su-ki;Yim, Chang Jae;Chung, Han Sub
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.6 no.1
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    • pp.83-88
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    • 2010
  • Domestic nuclear steam generators with Alloy 600 HTMA tubes have experienced axial cracking at eggcrate tube support plates(TSPs). The axial stress corrosion cracks were observed at the crevice between outside of tubes and eggcrate TSPs. The root cause of axial cracking was investigated by thermal hydraulic analysis and sludge distribution diagnosis. It is suggested that deposition of sludge at eggcrate TSPs could increase the outside surface temperature of tube and promote the enrichment of impurities at crevice, and thus accelerate cracking. Additionally strategy for reducing the sludge ingress to steam generators is discussed.

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Design Evaluation of Heavy Duty Heat Exchangers for Compact Steam Boilers (밀집형 증기보일러의 고부하 열교환기 설계평가)

  • Kim, Sungil;Yang, Jongin;Choi, Sangmin
    • Journal of the Korean Society of Combustion
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    • v.18 no.2
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    • pp.23-31
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    • 2013
  • Compact steam boiler is a useful heat exchanger in a space-intensive system. There are some constraints in terms of sizing and designing the space confined in the system which is usually used in vessels. In this study, design considerations for heavy duty heat exchangers of compact steam boilers are presented and evaluated. Especially, evaporator tubes of marine boiler which are exposed to a high temperature environment are considered. Also, extended surface designs with a high temperature are examined. In order to determine the criteria with considerations of both heat transfer rate and pressure drop in the heat exchanger, they are evaluated with major variables, such as the tube diameter, the number of tubes, and the tube length. Finally, the design parameters are estimated as the bare tubes are installed instead of the finned tubes.

A Review of Plugging Limit for Steam Generator Tubes in Nuclear Power Plants (원전 증기발생기 전열관 관막음 한계 고찰)

  • Kang, Yong Seok;Lee, Kuk Hee
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.16 no.2
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    • pp.10-17
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    • 2020
  • Securing the integrity of steam generator tubes is an essential requirement for safe operation of nuclear power plants. Therefore, tubes that do not satisfy integrity requirements are no longer usable and must be repaired according to the related requirements. In general, the repair criterion is that the damage depth is more than 40% of the tube wall thickness. However, the plugging limit can be changed and be applied, provided a technical proof is given that integrity can be secured against specific degradation at a specific plants and that approval can be obtained from a regulatory agency. A typical example is alternative repair criteria for defects within the tube sheet or tube support plates. In this paper, a background of establishing the plugging limit for steam generator tubes and changes in maintenance criteria are reviewed as examples.

Effects of Hydrophilic Surface Treatment on Evaporation Heat Transfer at the Outside Wall of Horizontal Tubes (친수성 표면처리가 수평관 외벽의 증발열전달에 미치는 영향)

  • 박노성;황규대;강병하;정진택
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.5
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    • pp.525-532
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    • 2000
  • Evaporation heat transfer characteristics have been investigated experimentally when distilled water is sprayed on the outside wall of horizontal tubes in a evaporator. This problem is of particular interest in the design of evaporator of an absorption system. Hydrophilic surface treatment was employed to increase the wettability on copper tubes. The results indicate that evaporation heat transfer with hydrophilic tubes is shown to be 25-44% higher than that with bare tubes at evaporation pressure of 31.8 Torr(evaporation temperature$ 30^{\circ}C). Evaporation heat transfer rates of hydrophilic treatment tubes are improved substantially, comparing with those of conventional copper tubes in the wide range of operating parameters, such as water inlet temperatures, water mass flow rates and evaporation pressures.

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The Burst Pressure Analysis of Steam Generator Tubes with Inclined Type of Wear Damage (경사형 마멸 손상부를 가진 증기발생기 전열관의 파열압력 해석)

  • Shin, Kyu-In;Park, Jai-Hak;Chung, Myung-Jo;Choi, Young-Hwan
    • Journal of the Korean Society of Safety
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    • v.19 no.2
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    • pp.11-15
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    • 2004
  • The fretting-fatigue by leaking is one of the significant degradation in steam generator tubes. In this study, the burst pressure of inclined damaged steam generator tubes were obtained from three criterions by using the finite element method. The analysis results were also compared with the experiment data from published references and they showed a good agreement with the experiment data.

Heat Transfer and Pressure Drop Characteristics for Various Tube Geometries in Modular Tube Bundle Heat Exchanger (모듈형 관군 열교환기에서의 관 형상에 따른 열전달 및 압력강하 특성에 관한 연구)

  • Yoon, Joon-Shik;Park, Byung-Kyu;Kim, Cham-Jung
    • Proceedings of the KSME Conference
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    • 2000.11b
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    • pp.105-111
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    • 2000
  • A numerical study has been performed to obtain the heat transfer and pressure drop characteristics for shell-and-tube heat exchanger with various shapes of tubes. The Tubes have variation of Aspect Ratio, Pitch and Rotation. Results are presented as plots of Colburn j factor and friction factor f against Aspect Ratio, Pitch and Rotation. As Aspect Ratio increases, j factor and f factor decreases. As Pitch increases, j factor decreases. j/f have optimized Pitch for each Aspect Ratio. Accordingly, there is fitness of Aspect Ratio and Pitch fur most effective cases. The Rotation of tubes are of no meaning for both heat transfer and pressure drop.

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Analysis of Burst Pressure for Wear-Damaged Steam Generator Tubes (마멸에 의해 손상된 증기발생기 전열관의 파열압력 해석)

  • Shin, Kyu-In;Park, Jai-Hak
    • Journal of the Korean Society of Safety
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    • v.18 no.4
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    • pp.16-22
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    • 2003
  • Generally the rupture of steam generator tubes proceeds from significant plastic deformation before failure. In this study, the burst pressures of damaged steam generator tubes were calculated from the plastic instability analysis with the finite element method. Two wear types, flat and circumferential types were considered. An equation for the burst pressure was proposed by using the strength reduction factor and the Svensson equation. The analysis results were compared with the experiment data from published references and they showed a good agreement with the experiment data.