• 제목, 요약, 키워드: Leak rate

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Estimation of Leak Rate Through Cracks in Bimaterial Pipes in Nuclear Power Plants

  • Park, Jai Hak;Lee, Jin Ho;Oh, Young-Jin
    • Nuclear Engineering and Technology
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    • v.48 no.5
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    • pp.1264-1272
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    • 2016
  • The accurate estimation of leak rate through cracks is crucial in applying the leak before break (LBB) concept to pipeline design in nuclear power plants. Because of its importance, several programs were developed based on the several proposed flow models, and used in nuclear power industries. As the flow models were developed for a homogeneous pipe material, however, some difficulties were encountered in estimating leak rates for bimaterial pipes. In this paper, a flow model is proposed to estimate leak rate in bimaterial pipes based on the modified Henry-Fauske flow model. In the new flow model, different crack morphology parameters can be considered in two parts of a flow path. In addition, based on the proposed flow model, a program was developed to estimate leak rate for a crack with linearly varying cross-sectional area. Using the program, leak rates were calculated for through-thickness cracks with constant or linearly varying cross-sectional areas in a bimaterial pipe. The leak rate results were then compared and discussed in comparison with the results for a homogeneous pipe. The effects of the crack morphology parameters and the variation in cross-sectional area on the leak rate were examined and discussed.

Leak Test for Propulsion System of Launch Vehicle (발사체 추진 시스템의 기밀시험)

  • Lim, Ha-Young;Han, Sang-Yeop;Yi, Moo-Keun
    • Aerospace Engineering and Technology
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    • v.11 no.2
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    • pp.103-108
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    • 2012
  • There is close correlation between the reliability of the launch vehicle and the leakage of the propellants or gases from the launch vehicle. This paper describes the definition of the leak rate to determine the quantity of the leakage and introduce the unit conversion of the leak rate. The main parameters for the leak rate were considered. The requirements for the gaseous for the leak test of launch vehicle and various leak test methods were introduced. Leak test method and procedure used in space launch vehicle were briefly described.

Numerical Investigation of the Effect of Crack Shape on Leak Flow Characteristics in Pipelines (누설 모양에 따른 파이프 누수 특성에 대한 수치 해석 연구)

  • Lee, Hyunmin;Kim, Jungwoo
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.26 no.2
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    • pp.238-242
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    • 2017
  • The effect of crack shape on the leak flow characteristics in pipelinesis investigated using computational fluid dynamics (CFD) simulations. In the present study, two different crack shapes are considered: axial crack andcircumferential crack. The present simulation results showed that under the same crack area, the aspect ratio influences the leak rate. When the aspect ratio is1, the leak rate reaches the minimum value. Moreover, the leak rate in the circumferentialcrack is slightly larger than that in the axial crack. The change in the leak rateaccording to the crack shape could be explained by the different velocitydistributions at the leak position depending on the aspect ratio.

A Study on the Simulation of Leak Flow-rate Using Isothermal Chamber (등온화용기를 이용한 누설유량 시뮬레이션에 관한 연구)

  • Ji, S.W.;Jang, J.S.
    • Journal of Power System Engineering
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    • v.14 no.5
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    • pp.71-75
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    • 2010
  • Leak detection technology is a challenging research until nowadays, because it has wide and various applications in industry. Furthermore pneumatic component reliability test based on ISO requires air leakage measurement. The conventional measurement methods need a complex operation and the calibration of leak detector. Tracing the history of our study, we proposed a new method for measurement of leak flow rate using isothermal chamber. In this study, propose a simulation model of isothermal chamber by infinitesimal flow -rate, such as a leak flow-rate. The effectiveness of the proposed simulation model is proved by simulation and experimental results. Base on the comparison results, proposed simulation model is good agreement with experimental results.

Study on Leak Rate of SCC Degraded Alloy 600 Tubings of PWRs

  • Hwang, Seong Sik;Kim, Joung Soo;Kasza, Ken E.;Park, Jangyul
    • Corrosion Science and Technology
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    • v.3 no.6
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    • pp.233-239
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    • 2004
  • Primary water stress corrosion cracking of steam generator tubings occur on many tubes in pressurized water reactors(PWRs), and they are repaired using sleeves or plugs. In order to develop proper repair criteria, it is necessary to know the leak behavior of the tubes, which have stress corrosion cracks. Crack development tests were carried out on the tubes at room temperature, and leak rate and burst pressure were measured on the degraded tubes at room temperature and a high temperature. No leakage was detected on the tubes where 100 % through wall crack developed, at 1560 psi, which is an operating pressure difference of pressurized water reactors(PWRs). In some tests, leak rates of the tubes increased with time at a constant internal water pressure. A test tube showed a very small amount of leakage at 2700 psi in a high temperature pressure test at $282^{\circ}C$, but it disappeared after the pressure increased slightly. Even cracks are 100 % through wall, they need to open in order to reach a certain amount of leak rate at the operating pressure difference.

Leakage Effect on the Exit Pressure in a Gas Pipeline (가스 파이프라인 내의 누출 현상이 출구 압력에 미치는 영향에 대한 연구)

  • Chang Seung-Yong
    • Journal of the Korean Institute of Gas
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    • v.10 no.3
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    • pp.27-33
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    • 2006
  • This paper investigates leak effect on the outlet pressure at pipeline exit. A modified Weymouth equation(including inclination effect) was used for this study. To investigate leak effect, outlet pressure and ratio of outlet to inlet pressure were compared between no leak and leak conditions for horizontal, upward and downward flows, respectively. Then, effects of leak location as well as leak rate on the outlet pressure were also investigated for all pipeline inclinations.

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Uncertainty Analysis of Containment Leak Rate Test System (격납건물 누설 시험장치의 불확실도 평가)

  • Lee, Kwang-Dae;Yang, Seung-Ok;Oh, Eung-Se
    • Proceedings of the KIEE Conference
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    • pp.635-637
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    • 2004
  • The containment of the nuclear power plant is the last barrier of radiation release when the reactor coolant pipe rupture is occurred. Each plant has to be tested every 5 years whether the containment leak rate meets its technical specifications. We have developed the leak rate test system and in this paper, we describe the results of the uncertainty analysis on the measurement channels and its propagation to the calculation results.

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High Temperature Gas Leak Behavior of Glass-Ceramic Fiber Composite Seals for SOFC Applications (SOFC용 유리-세라믹섬유 복합기밀재의 고온 기체누설 거동)

  • Lee, Jae-Chun;Kwon, Hyuk-Chon;Kwon, Young-Pil;Park, Sung;Jang, Jin-Sik;Lee, Jongho;Kim, Joosun;Lee, Hae-Won
    • Journal of the Korean Ceramic Society
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    • v.42 no.12
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    • pp.842-845
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    • 2005
  • Glass composites containing ceramic fiber have been developed for Solid Oxide Fuel Cell (SOFC) seals. Effect of glass type, loading pressure and thermal cycle the leak rates of composite seals was investigated. Seal performance of two commercial glasses was compared with that of $SiO_2BaO-B_2O_3$ glass synthesized in this work. The leak rate for seals made of pyrex(R) increases from $\~0.0005\;to\;\~0.004sccm/cm$ as the gas pressure increases from 10 to 50 kPa. The soda lime silicate glass seal shows the leak rate two times higher than the one made of pyrex(R) or $SiO_2BaO-B_2O_3$ glass. The viscosity of glass at the seal test temperature is presumed to affect the leak rate of the glass seal. As the applied loading pressure increases from 0.4 to 0.8 MPa at $750^{\circ}C$, the leak rate decreases from 0.038 to 0.024 sccm/cm for composite seals. It has been found that during 50 thermal cycles between $450^{\circ}C\;to\;700^{\circ}C$ leak rates remained almost constant, ranging from 0.025 to 0.03sccm/cm. The results showed an excellent thermal cycle stability as well as sealability of the glass matrix ceramic fiber composite seals.

Study on Leak Detection of the Pipeline System by Acoustic Emission (음향방출(音響放出)에 의한 배관계(配管系)의 누출방지(漏出防止)에 관한 연구(硏究))

  • Yoon, D.J.;Kim, C.J.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.7 no.1
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    • pp.7-17
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    • 1987
  • Leak detection testing for the pipeline system was performed by the acoustic emission method. It was found that the detected signal spectrum was influenced by the frequency response of sensors and pressure changes. AE parameters and frequency spectrum distributions were used to analyze the leak signals. The slope rise time of AE parameters were the important factors for distinguishing leak signals. The amplitude of leak signal was more affected by the changes of leak, rate and pressure than those of leak type.

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Elastic Crack Opening Displacement of Slanted Circumferential Through-Wall Cracks in Thick-Walled Cylinder (원주방향 경사관통균열이 존재하는 두꺼운 배관의 탄성 균열열림변위)

  • Han, Tae-Song;Huh, Nam-Su;Shim, Do-Jun;Kim, Jin-Su;Lee, Jin-Ho
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.8 no.3
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    • pp.13-22
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    • 2012
  • According to recent research on leak-rate estimates to assess rupture probabilities of nuclear piping which contains a circumferential surface/through-wall cracks due to PWSCC, i.e., xLPR (Extremely Low Probability of Rupture) program, it has been revealed that the use of crack shape with an idealized circumferential through-wall crack during actual crack growth can lead to overestimate of the leak-rate. Thus, for accurate estimation of the leak-rate during crack growth, the more realistic crack shape that can simulate the crack shape transition from surface crack to through-wall crack should be used. In this context, in the present study, the elastic crack opening displacement of slanted circumferential through-wall crack in thick-walled cylinder was proposed based on 3-dimensional elastic finite element fracture mechanics analyses. To propose the elastic crack opening displacement of slanted circumferential through-wall crack in thick-walled cylinder, the geometric variables affecting crack opening displacement, i.e., thickness of cylinder, reference inner crack length and slant crack ratio were systematically varied. In terms of loading conditions, axial tension, global bending moment and internal pressure were considered. The present results can be applied to calculate the leak-rate considering more realistic crack shape transition from surface crack to idealized through-wall crack, and can be expected to enhance current leak-rate estimation scheme, for instance, in xLPR program etc.