Environmental factor approach to account for water effects in pressure vessel and piping fatigue evaluations

Mehta, Hardayal S.; Gosselin, Stephen R.

doi:10.1016/s0029-5493(97)00344-0

Cited by 14 publications

(13 citation statements)

References 10 publications

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“…Either develop a new set of environmentally adjusted fatigue design curves 3,6,32 or use a fatigue life correction factor F en to adjust the current ASME Code fatigue usage values for environmental effects. 3,6,[11][12][13] For both approaches, the range and bounding values must be defined for key loading and environmental parameters that influence fatigue life. Estimates of fatigue life based on the two approaches may differ because of differences between the ASME mean curves used to develop the current design curves and the best-fit curves to the existing data that are used to develop the environmentally adjusted curves.…”

Section: Incorporating Environmental Effects Into Fatigue Evaluationsmentioning

confidence: 99%

“…11,12 The approach has recently been updated to include the revised statistical models and the PVRC discussions on evaluating environmental fatigue. 13 In the EPRI/GE approach, an "effective" fatigue life correction factor, expressed as F en,eff = F en /Z, is also defined, where Z is a factor that represents the perceived conservatism in the ASME Code design curves.…”

Section: Fatigue Life Correction Factormentioning

confidence: 99%

“…To incorporate environmental effects into the ASME Code fatigue evaluations, a fatigue usage for a specific load set, based on the current Code design curves, is multiplied by the correction factor. Specific expressions for F en , based on statistical models 6,[11][12][13] and on the correlations developed by the Environmental Fatigue Data Committee of the Thermal and Nuclear Power Engineering Society of Japan, 14 have been proposed.…”

Section: Introductionmentioning

confidence: 99%

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Mechanism and estimation of fatigue crack initiation in austenitic stainless steels in LWR environments.

Chopra¹

2002

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The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Figures I-9.1 through I-9.6 of Appendix I to Section III of the Code specify fatigue design curves for structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. Existing fatigue strain-vs.-life (e-N) data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. This report provides an overview of fatigue crack initiation in austenitic stainless steels in LWR coolant environments. The existing fatigue e-N data have been evaluated to establish the effects of key material, loading, and environmental parameters (such as steel type, strain range, strain rate, temperature, dissolved-oxygen level in water, and flow rate) on the fatigue lives of these steels. Statistical models are presented for estimating the fatigue e-N curves for austenitic stainless steels as a function of the material, loading, and environmental parameters. Two methods for incorporating environmental effects into the ASME Code fatigue evaluations are presented. The influence of reactor environments on the mechanism of fatigue crack initiation in these steels is also discussed. Executive SummarySection III, Subsection NB, of the ASME Boiler and Pressure Vessel Code contains rules for the design of Class 1 components of nuclear power plants. Figures I-9.1 through I-9.6 of Appendix I to Section III specify the Code design fatigue curves for applicable structural materials. However, Section III, Subsection NB-3121, of the Code states that effects of the coolant environment on fatigue resistance of a material were not intended to be addressed in these design curves. Therefore, the effects of environment on fatigue resistance of materials used in operating pressurized water reactor (PWR) and boiling water reactor (BWR) plants, whose primary-coolant pressure boundary components were designed in accordance with the Code, are uncertain.The current Section-III design fatigue curves of the ASME Code were based primarily on strain-controlled fatigue tests of small polished specimens at room temperature in air. Best-fit curves to the experimental test data were first adjusted to account for the effects of mean stress and then lowered by a factor of 2 on stress and 20 on cycles (whichever was more conservative) to obtain the design fatigue curves. These factors are not safety margins but rather adjustment factors that must be applied to experimental data to obtain estimates of the lives of components. They were not intended to address the effects of the coolant environment on fatigue life. Recent fatigue-strain-vs.-life (e-N) data obtained in the U.S. and Japan demonstrate that light water reactor (LWR) environments can have potentially significant effects on the fatigue resistance of materials. Specimen lives obtained from tests in simulated LWR environments can be much shorte...

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Section: Incorporating Environmental Effects Into Fatigue Evaluationsmentioning

confidence: 99%

Section: Fatigue Life Correction Factormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mechanism and estimation of fatigue crack initiation in austenitic stainless steels in LWR environments.

Chopra¹

2002

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“…Experimental data concerning the effect of water coolant on the cyclic strength o f carbon steels (CS), low-alloy steels (LAS) and austenitic stainless steels (SS) [3,[7][8][9][10][11][12] point to the possibility o f a considerable decrease in the number of cycles to failure under certain combined conditions of cyclic loading. In a general case, these are characterized by coolant temperature T, sulfur content S (CS, LAS), strain rate e, and oxygen concentration (OC) in the coolant.…”

Section: mentioning

confidence: 99%

“…For SS, e ath is estimated by various sources at 0.126 [12], 0.16 [7], and 0.18% [9], which is above the strain o f the fatigue limit for SS. It is noteworthy that the film and metal often have different mean stresses o f loading cycles, as restoration o f the oxide film after its rupture in the preceding half-cycle may occur under conditions of stressed metal.…”

Section: mentioning

confidence: 99%

Fatigue of NPP Components and Piping under Service Conditions

Филатов¹

2004

Strength of Materials

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The kinetics o f fatigue damage suffered by components of nuclear power facilities with light-water reactors is governed by a number o f simultaneous processes: a) unsteady-state loading (mechanical and thermal stresses) during transients, alternating in a general case with steady-state conditions and giving rise to a series o f loading half-cycles with various amplitudes and maximum stresses, which are separated by steady-state loading conditions with possible coincident vibrations; b) in-service variations of metal condition (loss of ductility due to ageing, coolant effects and irradiation, hardening or softening under cyclic elastic-plastic loading, radiation hardening, formation o f oxide films with properties dissimilar to those o f the metal); c) corrosive and mechanical interaction between coolant and metal (with possible deviation of water chemical composition from its nominal parameters during transients, faults in the water treatment system, local increase in the coolant corrosivity in stagnant zones, gaps and pockets with accumulation of sludge).It appears unrealistic to produce integrated models based on empirical data for accumulation of fatigue and corrosion fatigue damage in the component metal, with allowance for all the above processes, operational factors and their interaction. The equations employed to assess the condition of components in terms o f cumulative fatigue damage [1] are modified fatigue curve equations -of

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Fatigue Evaluation Considering the Environmental Influence Using A Monitoring System

Cicero

Gorrochategui

Álvarez

Fracture of Nano and Engineering Materials and Structures

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Environmental factor approach to account for water effects in pressure vessel and piping fatigue evaluations

Cited by 14 publications

References 10 publications

Mechanism and estimation of fatigue crack initiation in austenitic stainless steels in LWR environments.

Mechanism and estimation of fatigue crack initiation in austenitic stainless steels in LWR environments.

Fatigue of NPP Components and Piping under Service Conditions

Fatigue Evaluation Considering the Environmental Influence Using A Monitoring System

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