A probabilistic simulation of fluid leakage in multiple cracks situation

Xie, Liyang; Yu, Zhenliang

doi:10.1046/j.1460-2695.2002.00539.x

Cited by 4 publications

(2 citation statements)

References 37 publications

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“…It is beyond the scope of this paper to discuss further details on the leak rate modelling. The reader is referred to other papers such as Refs [9,10] and to section 'Modelling of the leak rates' for the particular empirical models employed in section 'Numerical examples'. The total leak rate Q T through n defects is then obtained as sum of individual contributions from a random number of l leakers and n − l leak-tight defects:…”

Section: Main Assumptionsmentioning

confidence: 99%

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Probabilistic evaluation of leak rates through multiple defects: the case of nuclear steam generators

Cizelj

Guy

2003

Fatigue Fract Eng Mat Struct

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A probabilistic approach aimed at predicting the probability of excessive leakage through flaws in tubes is proposed in the paper. The excessive leakage is assumed to occur when the sum of all individual leak rates through degraded tubes exceeds the predefined acceptable value. Additionally, a brief description of some estimators used in the field to obtain conservative estimates of the 95th percentile (e.g., upper limit) of the total leak rate is given. The conservatism of those estimators is quantified through failure probability in the two numerical examples. The leak rates through the individual flaws were evaluated using models developed by EPRI for assessment of outside diameter stress corrosion cracks (ODSCC) in tubes of steam generators in nuclear power plants assuming postulated hypothetical accidental conditions. The distributions of flaw sizes are based on inspection data obtained from Slovene and Belgian plants with 3/4 inch tubes made of Alloy 600 Mill Annealed. The numerical examples analyse the behaviour of the model for both small and large flaw sizes. The results include: prediction and discussion of the probability of excessive leakage; the conservatism of approximate estimators; comments on the sensitivity of the probability of excessive leakage to the major uncertainties inherent to data and models used. As a conclusion, some suggestions to improve both the efficiency of the numerical estimators and models used to estimate the leak rates through individual defects are given.

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Section: Main Assumptionsmentioning

confidence: 99%

“…It is beyond the scope of this paper to discuss further details on the leak rate modelling. The reader is referred to other papers such as Refs [9, 10] and to section ‘Modelling of the leak rates’ for the particular empirical models employed in section ‘Numerical examples’.…”

Section: Probability Of Excessive Leakagementioning

confidence: 99%

Probabilistic evaluation of leak rates through multiple defects: the case of nuclear steam generators

Cizelj

Guy

2003

Fatigue Fract Eng Mat Struct

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Explicit equations for leak rates through narrow cracks

Beck

Bagshaw

Yates

2005

International Journal of Pressure Vessels and Piping

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Explicit equations to describe the leak rate of a single phase fluid through a narrow crack under a low pressure gradient have been developed and are presented. Four distinct flow regimes, which change with crack opening displacement, have been previously identified and are the basis of this model. The fluid flow is governed by the pressure gradient and the tortuosity of the crack, which is particularly important when the opening displacement is small.The equations have been developed by considering the pressure forces created when the fluid flows down an idealised zig-zag channel. The nature of the flow, and hence the governing equations, change as the crack aperture increases.The power of this approach is clearly seen when the flow rates predicted using this model are compared both to the flow rates predicted from computational fluid dynamics analyses and those found by experimentation. The agreement between these sets of data is good, showing that the major effects governing the flow rate have been identified and accounted for.

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