ASME Code-Case Proposal to Explicitly Quantify the Interaction Between the PWR Environment and Component Surface Finish

2017 ◽  
Author(s):  
Thomas Métais ◽  
Stéphan Courtin ◽  
Laurent De Baglion ◽  
Cédric Gourdin ◽  
Jean-Christophe Le Roux
Keyword(s):  
Fatigue Life ◽  
Surface Finish ◽  
Polished Surface ◽  
Design Curve ◽  
Fatigue Design ◽  
Wide Range ◽  
Asme Code ◽  
The Difference ◽  
The Uk ◽  
Technical Basis

Fatigue rules from ASME have undergone a significant change over the past decade, especially with the inclusion of the effects of BWR and PWR environments on the fatigue life of components. The incorporation of the environmental effects into the calculations is performed via an environmental factor, Fen, which is introduced in ASME BPV code-case N-792 [5], and depends on factors such as the temperature, dissolved oxygen and strain rate. Nevertheless, a wide range of factors, such as surface finish, have a deleterious impact on fatigue life, but their contribution to fatigue life is typically taken through the transition factors to build the fatigue design curve [2] and not in an explicit way, such as the Fen factor. The testing supporting the rules pertaining to Environmental Fatigue Correction Factor (Fen) Method in ASME BPV was performed on specimens with a polished surface finish and on the basis that the Fen factor was applicable without alteration of the historical practice of building the design curve through transition factors. The extensive amount of testing conducted and reported in References [2] and [7] (technical basis for ASME BPV current EAF rules) was used to propose a set of transition coefficients from the mean air curve to the design curve on one hand, and on the other hand to build a Fen factor expression, defined as the difference between the life in air and in PWR environments. The work initiated by AREVA in 2005 [9] [10] [11] demonstrated that there is a clear interaction between the two aggravating effects of surface finish and PWR environment for fatigue damage, which was not experimentally tested in the References [2] and [7]. These results have clearly been supported by testing carried out independently in the UK by Rolls-Royce and AMEC FW [12]. These results are all the more relevant as most NPP components do not have a polished surface finish. Most surfaces are either industrially polished or installed as-manufactured. It was concluded that this proposal could potentially be applicable to a wide range of components and could be of interest to a wider community. EDF/Areva/CEA have therefore authored a code-case introducing the Fen-threshold, a factor which explicitly quantifies the interaction between PWR environment and surface finish. This paper summarizes this proposal and provides the technical background and experimental work to justify this proposal.

Explicit Quantification of the Interaction Between the PWR Environment and Component Surface Finish in Environmental Fatigue Evaluation Methods for Austenitic Stainless Steels

2018 ◽  
Author(s):  
Thomas Métais ◽  
Andrew Morley ◽  
Laurent de Baglion ◽  
David Tice ◽  
Gary L. Stevens ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
Surface Finish ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Polished Surface ◽  
Small Scale ◽  
Draft Code ◽  
Design Curve ◽  
Wide Range

Additional fatigue rules within the ASME Boiler and Pressure Vessel Code have been developed over the past decade or so, such as those in Code Case N-792-1 [1], which provides an acceptable method to describe the effects of BWR and PWR environments on the fatigue life of components. The incorporation of environmental effects into fatigue calculations is performed via an environmental factor, Fen, and depends on factors such as the temperature, dissolved oxygen and strain rate. In the case of strain rate, lower strain rates (i.e., from slow transients) aggravate the Fen factor which counters the long-held notion that step (fast) transients cause the highest fatigue usage. A wide range of other factors, such as surface finish, can have a deleterious impact on fatigue life, but their impact on fatigue life is typically considered by including transition sub-factors to construct the fatigue design curve from the mean behavior air curve rather than in an explicit way, such as the Fen factor. An extensive amount of testing and evaluation has been conducted and reported in References [2] [3] [4] [5] [6] [7] and [8] that were used to both revise the transition factors and devise the Fen equations contained in Code Case N-792-1. The testing supporting the definition of Fen was performed on small-scale laboratory specimens with a polished surface finish on the basis that the Fen factor is applicable to the design curve without any impact on the transition factors. The work initiated by AREVA in 2005 [4] [5] [6] suggested, in testing of austenitic stainless steels, an interaction between the two aggravating effects of surface finish and PWR environment on fatigue damage. These results have been supported by testing carried out independently in the UK by Rolls-Royce and AMEC Foster Wheeler (now Wood Group) [7], also on austenitic stainless steels. The key finding from these investigations is that the combined detrimental effects of a PWR environment and a rough surface finish are substantially less than the sum of the two individual effects. These results are all the more relevant as most nuclear power plant (NPP) components do not have a polished surface finish. Most NPP component surfaces are either industrially ground or installed as-manufactured. The previous studies concluded that explicit consideration of the combined effects of environment and surface finish could potentially be applicable to a wide range of NPP components and would therefore be of interest to a wider community: EDF has therefore authored a draft Code Case introducing a factor, Fen-threshold, which explicitly quantifies the interaction between PWR environment and surface finish, as well as taking some credit for other conservatisms in the sub-factors that comprise the life transition sub-factor used to build the design fatigue curve . The contents of the draft Code Case were presented last year [9]. Since then, other international organizations have also made progress on these topics and developed their own views. The work performed is applicable to Austenitic Stainless Steels only for the time being. This paper aims therefore to present an update of the draft Code Case based on comments received to-date, and introduces some of the research and discussions which have been ongoing on this topic as part of an international EPRI collaborative group on environmental fatigue issues. It is intended to work towards an international consensus for a final version of the ASME Code Case for Fen-threshold.

Further Evidence of Margin for Environmental Effects, Termed Fen-Threshold, in the ASME Section III Design Fatigue Curve for Austenitic Stainless Steels Through the Interaction Between the PWR Environment and Surface Finish

2020 ◽  
Author(s):  
Alec McLennan ◽  
Andrew Morley ◽  
Sam Cuvilliez
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Surface Finish ◽  
Environmental Effects ◽  
Fatigue Curve ◽  
Design Curve ◽  
High Temperature Water ◽  
Wide Range ◽  
The Mean ◽  
Temperature Water

Abstract Fatigue rules within the ASME Boiler and Pressure Vessel Code have undergone significant change over the past decade, especially with the inclusion of Code Case N-792-1 as an acceptable method to describe the effects of BWR and PWR environments on the fatigue life of components. The incorporation of the environmental effects into the fatigue calculations is performed using an environmental factor, Fen, which attempts to describe the difference in fatigue life of polished specimens between air and high-temperature water environments. The Fen depends on parameters such as the temperature, dissolved oxygen and strain rate. The deleterious effects on fatigue life of a wide range of other factors are not accounted for by the standard constant amplitude testing, performed on small polished specimens that was used to develop the mean air curve. These factors are accounted for in the design curve, which is defined by adjusting the mean air fatigue curve with transference factors. Evidence, obtained in recent years, now suggests that the assumed deleterious effect of surface finish on fatigue life may be excessive. Therefore, the combination of the air design fatigue curve and Fen results in overly-conservative estimates for fatigue life in high temperature water environments. Approaches have been developed to quantify the scale of this excess-conservatism and define this as a margin within the design fatigue curve that can be used to offset Fen. In the ASME framework this is termed Fen-Threshold. This paper presents further evidence in support of the approach by extending the database of test results to 316-type steels and extending the range of environmental and loading conditions. The additional stainless steel data demonstrates that the size of the margin is insensitive to strain amplitude over an extended range of strain amplitudes. Furthermore, the analysis indicates that in conditions where the environmental effect is low (less than the value of Fen-Threshold) the margin remains great enough to offset the entire Fen, returning such sites to an assessment against the air design curve. This paper also presents an extension of the research program to nickel based alloys through testing of Alloy 600. The intent is to investigate whether there is evidence of similar excessive conservatism that can be translated into an equivalent margin for environmental effects in nickel-based alloys.

Effect of Surface Condition on the Fatigue Life of Austenitic Stainless Steels in High Temperature Water Environments

2018 ◽  
Author(s):  
Andrew Morley ◽  
Marius Twite ◽  
Norman Platts ◽  
Alec McLennan ◽  
Chris Currie
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Rough Surface ◽  
Surface Finish ◽  
Water Environment ◽  
Austenitic Stainless Steels ◽  
Design Curve ◽  
Fatigue Design ◽  
High Temperature Water ◽  
Temperature Water

High temperature water environments typical of LWR operation are known to significantly reduce the fatigue life of reactor plant materials relative to air environments in laboratory studies. This environmental impact on fatigue life has led to the issue of US-NRC Regulatory Guide 1.207 [1] and supporting document NUREG/CR-6909 [2] which predicts significant environmental reduction in fatigue life (characterised by an environmental correction factor, Fen) for a range of actual and design basis transients. In the same report, a revision of the fatigue design curve for austenitic stainless steels and Ni-Cr-Fe alloys was proposed [2]. This was based on a revised mean curve fit to laboratory air data and revised design factors to account for effects not present in the test database, including the effect of rough surface finish. This revised fatigue design curve was endorsed by the NRC for new plant through Regulatory Guide 1.207 [1] and subsequently adopted by the ASME Boiler and Pressure Vessel (BPV) Code [3]. Additional rules for accounting for the effect of environment, such as the Fen approach, have been included in the ASME BPV Code as code cases such as Code Case N-792-1 [4]. However, there is a growing body of evidence [5] [6] [7] and [8] that a rough surface condition does not have the same impact in a high temperature water environment as in air. Therefore, application of Fen factors with this design curve may be unduly conservative as it implies a simple combination of the effects of rough surface and environment rather than an interaction. Explicit quantification of the interaction between surface finish and environment is the aim of a number of recent proposals for improvement to fatigue assessment methods, including a Rule in Probationary Phase in the RCC-M Code and a draft Code Case submitted to the ASME BPV Code as described in References [9] and [10]. These approaches aim to quantify the excessive conservatism in current methods due to this unrecognised interaction, describing this as an allowance for Fen effectively built into the design curve. A number of approaches in various stages of development and application are discussed further in a separate paper at this conference [11]. This paper reports the results of an extensive programme of strain-controlled fatigue testing, conducted on two heats of well-characterised 304-type material in a high-temperature simulated PWR environment by Wood plc. The baseline behaviour in environment of standard polished specimens is compared to that of specimens with a rough surface finish bounding normal plant component applications. The results reported here substantially add to the pool of data supporting the conclusion that surface finish effects in a high-temperature water environment are significantly lower than the factor of 2.0 to 3.5 assumed in construction of the current ASME III fatigue design curve. This supports the claim made in the methods discussed in [9] [10] and [11] that the fatigue design curve already incorporates additional conservatism for a high-temperature water environment that can be used to offset the Fen derived by the NUREG/CR-6909 methodology. At present, this observation is limited to austenitic stainless steels.

scholarly journals Gauge-Strain-Controlled Air and PWR Fatigue Life Data for 304 Stainless Steel—Some Effects of Surface Finish and Hold Time

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1248
Author(s):  
Marc Vankeerberghen ◽  
Michel De Smet ◽  
Christian Malekian
Keyword(s):  
Fatigue Life ◽  
Surface Finish ◽  
Fatigue Testing ◽  
Hold Time ◽  
Ground Surface ◽  
Fatigue Curve ◽  
304 Stainless Steel ◽  
Polished Surface ◽  
Water Reactor ◽  
Primary Water

We performed environmental fatigue testing in simulated primary water reactor (PWR) primary water and reference fatigue testing in air in the framework of an international, collaborative project (INCEFA-PLUS), where the effects of mean strain and stress, hold time, strain amplitude and surface finish on fatigue life of austenitic stainless steels in light water reactor environments are being studied. Our fatigue lives obtained on machined specimens in air at 300 °C lie close to the NUREG/CR6909 mean air fatigue curve and are in line with INCEFA-PLUS air fatigue lives. Our environmental fatigue lives obtained in simulated PWR primary water at 300 °C lie relatively close to the NUREG/CR6909 mean fatigue curve; derived from the NUREG/CR6909 mean air fatigue curve and the applicable environmental correction factor (Fen). The PWR results show that (1) a polished surface finish has a slightly higher and a ground surface finish a slightly lower fatigue life than the NUREG/CR6909 prediction; (2) the ratio of polished to ground specimen life is ~1.37 at 300 °C and ~1.47 at 230 °C; (3) holds—at zero strain after a positive strain-rate—have a slightly detrimental effect on fatigue life. These results are in line with the INCEFA-PLUS PWR fatigue lives. A novel gauge-strain extensometer was deployed in order to perform a true gauge-strain-controlled fatigue test in simulated PWR primary water.

Margins for ASME Code Fatigue Design Curve: Effects of Surface Finish and Material Variability

2003 ◽  
Author(s):  
O. K. Chopra ◽  
W. J. Shack
Keyword(s):  
Pressure Vessel ◽  
Nuclear Power ◽  
Environmental Parameters ◽  
Light Water Reactor ◽  
Code Design ◽  
Low Alloy Steels ◽  
Design Curve ◽  
Fatigue Design ◽  
Asme Code ◽  
Alloy Steels

The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. This Code specifies 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 (ε-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 the existing fatigue ε-N data for carbon and low-alloy steels and wrought and cast austenitic SSs to define the effects of key material, loading, and environmental parameters on the fatigue lives of the steels. Experimental data are presented on the effects of surface roughness on the fatigue life of these steels in air and LWR environments. Statistical models are presented for estimating the fatigue ε-N curves as a function of the material, loading, and environmental parameters. Two methods for incorporating environmental effects into the ASME Code fatigue evaluations are discussed. Data available in the literature have been reviewed to evaluate the conservatism in the existing ASME Code fatigue evaluations. A critical review of the margins for the ASME Code fatigue design curve is presented.

Fatigue Consideration of Layered Vessels

2020 ◽  
Author(s):  
Kang Xu ◽  
Mahendra Rana ◽  
Maan Jawad
Keyword(s):  
Fatigue Life ◽  
Structural Integrity ◽  
Cost Effective ◽  
Pressure Vessels ◽  
Asme Code ◽  
Section Viii ◽  
Cyclic Service ◽  
Gap Height ◽  
Technical Basis ◽  
Division 2

Abstract Layered pressure vessels provide a cost-effective solution for high pressure gas storage. Several types of designs and constructions of layered pressure vessels are included in ASME BPV Section VIII Division 1, Division 2 and Division 3. Compared with conventional pressure vessels, there are two unique features in layered construction that may affect the structural integrity of the layered vessels especially in cyclic service: (1) Gaps may exist between the layers due to fabrication tolerances and an excessive gap height introduces additional stresses in the shell that need to be considered in design. The ASME Codes provide rules on the maximum permissible number and size of these gaps. The fatigue life of the vessel may be governed by the gap height due to the additional bending stress. The rules on gap height requirements have been updated recently in Section VIII Division 2. (2) ASME code rules require vent holes in the layers to detect leaks from inner shell and to prevent pressure buildup between the layers. The fatigue life may be limited by the presence of stress concentration at vent holes. This paper reviews the background of the recent code update and presents the technical basis of the fatigue design and maximum permissible gap height calculations. Discussions are made in design and fabrication to improve the fatigue life of layered pressure vessels in cyclic service.

scholarly journals Implementation of a chemical background method for atmospheric OH measurements by laser-induced fluorescence: characterisation and observations from the UK and China

2020 ◽  
Vol 13 (6) ◽  
pp. 3119-3146 ◽  
Author(s):  
Robert Woodward-Massey ◽  
Eloise J. Slater ◽  
Jake Alen ◽  
Trevor Ingham ◽  
Danny R. Cryer ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Ambient Air ◽  
Laser Induced Fluorescence ◽  
Excitation Wavelength ◽  
Atmospheric Conditions ◽  
Wide Range ◽  
Model Predictions ◽  
The Difference ◽  
The Uk ◽  
Interference Tests

Abstract. Hydroxyl (OH) and hydroperoxy (HO2) radicals are central to the understanding of atmospheric chemistry. Owing to their short lifetimes, these species are frequently used to test the accuracy of model predictions and their underlying chemical mechanisms. In forested environments, laser-induced fluorescence–fluorescence assay by gas expansion (LIF–FAGE) measurements of OH have often shown substantial disagreement with model predictions, suggesting the presence of unknown OH sources in such environments. However, it is also possible that the measurements have been affected by instrumental artefacts, due to the presence of interfering species that cannot be discriminated using the traditional method of obtaining background signals via modulation of the laser excitation wavelength (“OHwave”). The interference hypothesis can be tested by using an alternative method to determine the OH background signal, via the addition of a chemical scavenger prior to sampling of ambient air (“OHchem”). In this work, the Leeds FAGE instrument was modified to include such a system to facilitate measurements of OHchem, in which propane was used to selectively remove OH from ambient air using an inlet pre-injector (IPI). The IPI system was characterised in detail, and it was found that the system did not reduce the instrument sensitivity towards OH (< 5 % difference to conventional sampling) and was able to efficiently scavenge external OH (> 99 %) without the removal of OH formed inside the fluorescence cell (< 5 %). Tests of the photolytic interference from ozone in the presence of water vapour revealed a small but potentially significant interference, equivalent to an OH concentration of ∼4×105 molec. cm−3 under typical atmospheric conditions of [O3] =50 ppbv and [H2O] =1 %. Laboratory experiments to investigate potential interferences from products of isoprene ozonolysis did result in interference signals, but these were negligible when extrapolated down to ambient ozone and isoprene levels. The interference from NO3 radicals was also tested but was found to be insignificant in our system. The Leeds IPI module was deployed during three separate field intensives that took place in summer at a coastal site in the UK and both in summer and winter in the megacity of Beijing, China, allowing for investigations of ambient OH interferences under a wide range of chemical and meteorological conditions. Comparisons of ambient OHchem measurements to the traditional OHwave method showed excellent agreement, with OHwave vs OHchem slopes of 1.05–1.16 and identical behaviour on a diel basis, consistent with laboratory interference tests. The difference between OHwave and OHchem (“OHint”) was found to scale non-linearly with OHchem, resulting in an upper limit interference of (5.0±1.4) ×106 molec. cm−3 at the very highest OHchem concentrations measured (23×106 molec. cm−3), accounting for ∼14 %–21 % of the total OHwave signal.

Proposed ASME Code High Cycle Fatigue Design Curves for Austenitic and Ferritic Steels

2017 ◽  
Author(s):  
Sampath Ranganath ◽  
Hardayal S. Mehta ◽  
Nathan A. Palm ◽  
John Hosler
Keyword(s):  
High Cycle Fatigue ◽  
Ferritic Steels ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Design Curve ◽  
Fatigue Design ◽  
Asme Code ◽  
The Mean ◽  
Number Of Cycles ◽  
Fatigue Evaluation

The ASME Code fatigue curves (S–N curves) are used in the fatigue evaluation of reactor components. For the assessment of high frequency cyclic loading (such as those produced by flow-induced vibrations), where the number of cycles is expected to be very large and cannot be estimated, the stresses are evaluated by comparison with the fatigue limit1 at 1011 cycles. Other high cycle events of finite time duration (e.g. safety relief loading), where the number of cycles is large but well defined, the fatigue evaluation is performed by comparing the calculated stress with the allowable values defined by the high cycle fatigue design curve. This paper discusses the development of fatigue design curves for austenitic and ferritic steels when the number of cycles is in the range 106 – 1011 cycles. The first part of the paper addresses austenitic stainless steel components which are used for reactor internals. Specifically, the approach described here uses temperature dependent properties (cyclic yield strength, cyclic ultimate strength) for the mean stress correction and the correction for the modulus of elasticity. The high cycle fatigue design curve is developed by applying the mean stress and the E correction on the reversing load mean data curve and applying a factor of 2 on stress. The generic methodology developed for austenitic steel was applied to carbon and low alloy steels also. The proposed fatigue design curves are part of a draft ASME Code Case being considered by the ASME Code Subgroup on Design Methods. This paper describes the technical basis for the proposed ASME Code Case for the high cycle fatigue design curves for austenitic and ferritic steels.

3. The Rule of Law

2017 ◽  
Author(s):  
Brian Thompson ◽  
Michael Gordon
Keyword(s):  
Rule Of Law ◽  
The Rule Of Law ◽  
Legal Principles ◽  
Constitutional Principle ◽  
Wide Range ◽  
The Difference ◽  
The Uk

Extracts have been chosen from a wide range of historical and contemporary cases to illustrate the reasoning processes of the courts and to show how legal principles are developed. This chapter discusses the constitutional principle of the rule of law. First the rule of law is introduced, and then Dicey's understanding of it, and criticism of this, is considered. The difference between formal and substantive understandings of the rule of law is discussed, then the rule of law as a broad political doctrine, and finally what is meant by the idea of government according to law in the UK.

Environmental Fatigue Evaluation of a Korean Nuclear Power Plant

2008 ◽  
Author(s):  
Chang-Kyun Oh ◽  
Hyun-Su Kim ◽  
Hag-Ki Youm ◽  
Tae-Eun Jin ◽  
Young-Jin Kim
Keyword(s):  
Fatigue Life ◽  
Pressure Vessel ◽  
Nuclear Power ◽  
Reactor Pressure Vessel ◽  
Moment Stress ◽  
Wide Range ◽  
Class 1 ◽  
Asme Code ◽  
Fatigue Evaluation ◽  
Reactor Pressure

In accordance with the recommendation of USNRC and the U.S. license renewal experiences, the effects of reactor coolant environment on the fatigue life have to be considered for the continued operation of operating nuclear power plants as well as for the design of new plants. Although various evaluation methodologies have been suggested to date, a wide range of comparison of the existing methodologies has not been performed. The purpose of this paper is to evaluate the environmental effects on the fatigue life of a reactor pressure vessel and ASME Class 1 piping by the various methodologies and to investigate the effects of the pressure and moment stress histories on the environmental fatigue evaluation. The evaluation results show that the environmental fatigue evaluation results based on the design cumulative usage factors for the reactor pressure vessel and ASME Class 1 piping satisfy the requirement of the ASME code except for charging nozzle. However, when using operating cumulative usage factor, the environmental fatigue evaluation result for the charging nozzle satisfies the ASME code allowable. And the effects of the pressure and moment stress histories on the environmental fatigue evaluation are considered to be small when using the modified rate approach.

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