Probabilistic Analysis of 60-Year Environmental Fatigue Effects for Reactor Components

2003 ◽  
Author(s):  
Arthur F. Deardorff ◽  
Dilip Dedhia ◽  
Stan T. Rosinski ◽  
David O. Harris
Keyword(s):  
Environmental Effects ◽  
Fatigue Testing ◽  
Fatigue Curve ◽  
Light Water Reactor ◽  
Operating Period ◽  
Detailed Review ◽  
Core Damage ◽  
Fatigue Initiation ◽  
Mechanics Analysis ◽  
Stress Variance

In NUREG/CR-6674, a probabilistic fracture mechanics analysis was conducted to assess the effects of light water reactor environmental effects on the probability of fatigue initiation and subsequent crack growth leading to leakage and possible core damage. The results were based on stresses for typical locations in BWR and PWR reactors as determined from an analysis reported in NUREG/CR-6260. Although environmental effects were shown to have an insignificant effect on core damage frequency, the study concluded that there could be a significant increase in probability of leakage. A detailed review of the methodology and input conditions used in NUREG/CR-6674 has been completed, including use of an altered probabilistic fatigue curve with more representative high-cycle stress variance and consideration of results from more recent environmental fatigue testing. This revised analysis indicates that environmental effects on the probability of leakage and core damage frequency in an extended nuclear plant operating period are significantly less than previously reported in NUREG/CR-6674. This paper summarizes the analysis performed and the results obtained.

Low Cycle Fatigue (EAF) of AISI 304L and 347 in PWR Water

2018 ◽  
Author(s):  
Tommi Seppänen ◽  
Jouni Alhainen ◽  
Esko Arilahti ◽  
Jussi Solin
Keyword(s):  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Fatigue Curve ◽  
Light Water Reactor ◽  
Cycle Fatigue ◽  
Aisi 304L ◽  
Publication Data ◽  
Asme Code ◽  
Temperature And Pressure ◽  
Experimental Challenge

The update of the ASME III design fatigue curve for stainless steel in conjunction with the Fen model described in the NUREG/CR-6909 report has been criticized since publication. Data used to develop curves and models raises more questions than it answers. Material testing in a simulated light water reactor environment is difficult due to the temperature and pressure involved. The experimental challenge makes it tempting to take shortcuts where they should least be taken. Facing and overcoming the challenges, direct strain-controlled fatigue testing has been performed at VTT using a unique tailored-for-purpose EAF facility. The applicable ASTM standards E 606 and E1012 are followed to provide results that are directly compatible with ASME Code Section III. Several earlier PVP papers (PVP2016-63291, PVP2017-65374) report lower than calculated experimental Fen factors for stabilized stainless steels. In this paper new results, in line with the previous years’ conclusions, are presented for nonstabilized AISI 304L tested with dual strain rate waveforms. To model environmental effects more accurately, an approach accounting for the damaging effect of plastic strain is proposed. A draft Fen model, similar in structure to the NUREG model but with additional parameters, is shown to significantly improve the accuracy of Fen prediction.

Status of French Road Map to Improve Environmental Fatigue Rules

2012 ◽  
Author(s):  
Claude Faidy
Keyword(s):  
Stainless Steel ◽  
Environmental Effects ◽  
Fatigue Curve ◽  
Fatigue Tests ◽  
Stress Effects ◽  
The Past ◽  
Road Map ◽  
The Status ◽  
Load Effects ◽  
Section Viii

During the past 30 years many fatigue tests and fatigue analysis improvements have been developed in France in order to improve Codified Fatigue Rules of RCC-M and ASME Codes [1, 2]. This paper will present the major technical improvements to obtain reasonable evaluation of potential fatigue damage through EDF road map. Recently new results [3] confirm possible un-conservative fatigue material data: - High cycle fatigue in air for stainless steel, - Environmental effects on fatigue S-N curve for all materials - Fatigue Crack Growth law under PWR environment for stainless steel. In front of these new results, EDF has developed a “Fatigue Road Map” to improve the different steps of Codified fatigue rules. A periodic up-dating of proposed rules in the different French Codes: RCC-M, RCC-MRx and RSE-M with research of harmonization with other Code rules developed in USA, Japan and Germany in particular, will be done on a yearly basis. During the past 15 years, many results have been obtained through fatigue tests of stainless steel materials: - mean and design fatigue curve in air, - environmental effects on fatigue curves, - plasticity effects, - bi-axial load effects, - mean stress effects, - stress indices, - transferability from small to large specimen, - weld versus base metal. In parallel, many new developments have been made in non-nuclear pressure equipment industry: like the reference stress of ASME Section VIII or the structural stress of EN 13445. These methods are mainly well adapted to fatigue pressure cycling. In front of that situation, the French nuclear code organization needs to propose reliable rules for new design and for operating plants. Different proposals are under discussion and the status of the EDF proposals are presented in the paper. The consequences could be important for the utilities because a large part of the in-service inspection program is connected to some fatigue usage factor level between 0.5 and 1.

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.

Guidelines on Environmental Fatigue Evaluation for LWR Component

2003 ◽  
Author(s):  
Takao Nakamura ◽  
Itaru Saito ◽  
Yasuhide Asada
Keyword(s):  
Environmental Effects ◽  
Nuclear Power ◽  
Reduction Factor ◽  
Engineering Society ◽  
Fatigue Initiation ◽  
Plant Life ◽  
Actual Operating ◽  
Fatigue Evaluation ◽  
Fatigue Life Reduction ◽  
Operating Plant

Japanese utilities and vendors have taken environmental effects on fatigue (EF) into consideration in the plant life management (PLM) activity of operating plants for several years. In Sep. 2000 MITI notified the utilities to adopt “The Guidelines for Evaluating Fatigue Initiation Life Reduction in LWR Environment (MITI guidelines)” for PLM evaluation of operating plants [1]. In April 2001, the study started to establish detailed procedures for EF evaluation and the committee was organized for developing detailed guidelines at Thermal and Nuclear Power Engineering Society (TENPES). The evaluation guidelines were completed and published as TENPES guidelines [2]. These guidelines proposed several practical options to apply fatigue life reduction factor for environmental effects (Fen) on actual operating plant fatigue evaluation.

Fatigue of Stainless Steel Components: Toward Codified Rules Improvements

2013 ◽  
Author(s):  
Claude Faidy
Keyword(s):  
Stainless Steel ◽  
Fatigue Crack ◽  
Environmental Effects ◽  
Stainless Steels ◽  
High Cycle Fatigue ◽  
Fatigue Curve ◽  
Fatigue Tests ◽  
Correction Factors ◽  
Cycle Fatigue ◽  
The Past

During the past 30 years many fatigue tests and fatigue analysis improvements have been developed in France in order to improve Codified Fatigue Rules of French Nuclear Codes: RCC-M, RSE-M and RCC-MRx. This paper will present comments and proposals for development of these rules associated to Gaps and Needs in order to finalize and justify the AFCEN Codes new rules. Recently 3 new international R&D results confirm possible un-conservative fatigue material data: - High cycle fatigue in air for stainless steel, - Environmental effects on fatigue S-N curve for all materials, and in particular stainless steels, - Fatigue Crack Growth law under PWR environment for stainless steel. In front of these new results, AFCEN is working on a 1st set of rules based on existing knowledge: - Air fatigue curve: mean and design - PWR Environmental effects with detrimental correction factors A periodic up-dating of AFCEN proposed rules will be done using French and International R&D programs with a particular attention on harmonization with other Code rules developed in USA, Japan and Germany, in particular.

Environmental Assisted Fatigue and EDF 900 MWe PWRs Fleet: Towards an Exemption of Environmental Effects Consideration for Secondary Circuit Components

2018 ◽  
Author(s):  
Sam Cuvilliez ◽  
Gaëlle Léopold ◽  
Thomas Métais
Keyword(s):  
Environmental Effects ◽  
Nuclear Power ◽  
Power Plants ◽  
Fatigue Loading ◽  
Degradation Process ◽  
Fatigue Curve ◽  
Primary Circuit ◽  
Secondary Circuit ◽  
Technical Specifications ◽  
Circuit Components

Environmentally Assisted Fatigue (EAF) is receiving nowadays an increased level of attention for existing Nuclear Power Plants (NPPs) as utilities are now working to extend their life. In the wake of numerous experimental fatigue tests carried out in air and also in a PWR environment, the French RCC-M code [1] has recently been amended (in its 2016 edition) with two Rules in Probatory Phase (RPP), equivalent to ASME code-cases, “RPP-2” and “RPP-3” [2] [3]. RPP-2 consists of an update of the design fatigue curve in air for stainless steels (SSs) and nickel-based alloys, and is also associated with RPP-3 which provides guidelines for incorporating the environmental penalty “Fen” factor in fatigue usage factor calculations. Alongside this codification effort, an EAF screening has recently been carried out within EDF DT [4] on various areas of the primary circuit of the 900 MWe plants of the EDF fleet. This screening led to the identification of a list of 35 “sentinel locations” which are defined as areas most prone to EAF degradation process. These locations will be subjected to detailed EAF analysis in the stress report calculations (according to the above-mentioned RCC-M code cases) for the fourth decennial inspection of the 900 MWe (VD4 900 MWe) power plants. The potential impact of EAF on the secondary circuit components is another question to address in anticipation of the VD4 900 MWe, as they may be considered as class 1 or class 2 equipment for RCC-M application according to the equipment specification. This paper presents the approach proposed by EDF towards an exemption of environmental effects consideration for secondary circuit components. The argument is first based on a review of experimental campaigns led in Japan and France (respectively on fatigue test specimens and at the component scale) which indicate a Dissolved Oxygen (DO) content threshold below which environmental effects are almost inexistent. The (conservative) value of 40 ppb has been selected consistently with NUREG/CR-6909 revision 0 [5]. The second part of the argument is built, on the one hand, on the analysis of the EDF Technical Specifications for Operation (STE) which narrows the scope of the study only to unit outages, and, on the other hand, on the analysis of 5 years of operations of all 900 MWe plants of the EDF fleet (equivalent to 170 reactor-years). It has been shown that the DO content rarely exceeded the 40 ppb threshold in the secondary coolant, and that in this case, the considered locations were not submitted to any fatigue loading.

EDF/NRC High-Cycle Fatigue Database Proposal

2015 ◽  
Author(s):  
T. P. Métais ◽  
G. Stevens ◽  
G. Blatman ◽  
J. C. Le Roux ◽  
R. L. Tregoning
Keyword(s):  
Stainless Steels ◽  
Data Exchange ◽  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Austenitic Stainless Steels ◽  
Nuclear Regulatory Commission ◽  
Fatigue Curve ◽  
Research Data ◽  
Cycle Fatigue ◽  
Fatigue Data

Revised fatigue curves for austenitic stainless steels are currently being considered by several organizations in various countries, including Japan, South Korea, and France. The data available from laboratory tests indicate that the mean air curve considering all available austenitic material fatigue data may be overly conservative compared to a mean curve constructed from only those data representative of a particular type of material. In other words, developing separate fatigue curves for each of the different types of austenitic materials may prove useful in terms of removing excess conservatism in the estimation of fatigue lives. In practice, the fatigue curves of interest are documented in the various international design codes. For example, in the 2009 Addenda of Section III of the ASME Boiler and Pressure Vessel (BPV) Code [1], a revised design air fatigue curve for austenitic materials was implemented that was based on NRC research models [2]. More recently, in Japan, various industrial groups have joined their efforts to create the Design Fatigue Curve Sub-committee (DCFS) with the objective to reassess the fatigue curves [3]. In France, EDF/AREVA and CEA are developing a new fatigue curve for austenitic stainless steels [4]. More specifically, in 2014, EDF presented a paper on high-cycle fatigue analysis which demonstrated that the factor on the strain amplitude could be reduced from 2 to 1.4 for the RCC-M austenitic stainless steel grades [5]. Recently, discussions between EDF and the U.S. Nuclear Regulatory Commission (NRC) have led both parties to recognize that there is a need to exchange worldwide research data from fatigue testing to promote a common, vetted database available to all researchers. These discussions have led EDF and NRC to pursue a collaborative agreement and associated fatigue data exchange, with the intent to assemble all available fatigue data for austenitic materials into a standardized format. The longer term objective is to perform common analyses on the consolidated set of data. This paper summarizes the intent and of the preliminary results of this cooperation and also provides insights from both organizations on possible future activities and participation in the global exchange of fatigue research data.

Determination of Fatigue Limit by Locati Methodusing S-N Curve Determined by Means of Thermographic Method

2014 ◽  
Vol 223 ◽  
pp. 362-373 ◽  
Author(s):  
Adam Lipski
Keyword(s):  
Fatigue Limit ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Fatigue Curve ◽  
Rotational Frequency ◽  
Automatic Equipment ◽  
Staircase Method ◽  
New Approach ◽  
Combined Application

Selected results of experimental research showing possibilities to combined accelerated methods, i.e. thermographic determination of the fatigue curve and estimating the fatigue limit, were presented in this paper. The tests were performed using the reversed bending fatigue-testing machine with a rotational frequency of 77 Hz. The main item of the test station was the thermographic camera. Test specimens were made of C45 (1.0503) steel drawn bars. The full tests results were presented for the fatigue S-N curve (23 specimens at 10 load levels) and fatigue limit by the Staircase method (25 specimens) based on 107 cycles to failure was determination. The accelerated test for determining the slope of the S-N curve and the fatigue limit were made by a single specimen based on gradually increasing loading. Methods previously presented in the literature are based on the phenomenon of temperature stabilization during most of the fatigue process. The results presented in this work did not show the occurrence of such a phenomenon. For that reason, the new approach to the determination of the slope of S-N curve was proposed. Combined application of both experimental methods, Locati and thermographic, with a new approach to the determination of this slope might allow one to develop automatic equipment for the accelerated determination of the fatigue limit which would contribute to significant reduction of the test costs and time, thus increasing availability of such tests.

Sign in / Sign up

Export Citation Format

Share Document