Regulatory Guide 1.207
| ML070380586 | |
| Person / Time | |
|---|---|
| Issue date: | 03/23/2007 |
| Revision: | 0 |
| From: | NRC/RES/DFERR/DDME/CMB |
| To: | |
| Gonzalez H, NRC/RES/DFERR, 415-0068 | |
| Shared Package | |
| ML070380150 | List: |
| References | |
| DG-1144 RG-1.207 | |
| Download: ML070380586 (7) | |
The U.S. Nuclear Regulatory Commission (NRC) issues regulatory guides to describe and make available to the public methods that the NRC staffconsiders acceptable for use in implementing specific parts of the agency's regulations, techniques that the staff uses in evaluating specific problemsor postulated accidents, and data that the staff need in reviewing applications for permits and license Regulatory guides are not substitutesfor regulations, and compliance with them is not require Methods and solutions that differ from those set forth in regulatory guides will be deemedacceptable if they provide a basis for the findings required for the issuance or continuance of a permit or license by the Commission.This guide was issued after consideration of comments received from the publi The NRC staff encourages and welcomes comments and suggestionsin connection with improvements to published regulatory guides, as well as items for inclusion in regulatory guides that are currently being developed. The NRC staff will revise existing guides, as appropriate, to accommodate comments and to reflect new information or experienc Written commentsmay be submitted to the Rules and Directives Branch, Office of Administration, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.Regulatory guides are issued in 10 broad divisions: 1, Power Reactors; 2, Research and Test Reactors; 3, Fuels and Materials Facilities;4, Environmental and Siting; 5, Materials and Plant Protection; 6, Products; 7, Transportation; 8, Occupational Health; 9, Antitrust and Financial Review;and 10, General.Requests for single copies of draft or active regulatory guides (which may be reproduced) should be made to the U.S. Nuclear Regulatory Commission,Washington, DC 20555, Attention: Reproduction and Distribution Services Section, or by fax to (301) 415-2289; or by email to Distribution@nrc.gov. Electronic copies of this guide and other recently issued guides are available through the NRC's public Web site under the Regulatory Guides documentcollection of the NRC's Electronic Reading Room at http://www.nrc.gov/reading-rm/doc-collections/ and through the NRC's Agencywide DocumentsAccess and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under Accession No. ML070380586.U.S. NUCLEAR REGULATORY COMMISSIONMarch 2007REGULATORY GUIDEOFFICE OF NUCLEAR REGULATORY RESEARCHREGULATORY GUIDE 1.207(Draft was issued as DG-1144, dated July 2006)GUIDELINES FOR EVALUATING FATIGUE ANALYSESINCORPORATING THE LIFE REDUCTIONOF METAL COMPONENTSDUE TO THE EFFECTS OF THE LIGHT-WATER REACTORENVIRONMENT FOR NEW REACTORS INTRODUCTIONIn Appendix A, "General Design Criteria for Nuclear Power Plants," to Title 10, Part 50, ofthe Code of Federal Regulations (10 CFR Part 50), "Domestic Licensing of Production and UtilizationFacilities" (Ref. 1), General Design Criterion (GDC) 1, "Quality Standards and Records," requires, in part, that structures, systems, and components that are important to safety shall be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety function performe In addition, GDC 30, "Quality of Reactor Coolant Pressure Boundary," requires, in part, that components that are part of the reactor coolant pressure boundary shall be designed, fabricated, erected, and tested to the highest practical quality standards.Augmenting those design criteria, 10 CFR 50.55a, "Codes and Standards," endorsesthe American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Ref. 2)
for design of safety-related systems and component In particular, Section 50.55a(c), "Reactor Coolant Pressure Boundary," requires, in part, that components of the reactor coolant pressure boundary must meetthe requirements for Class 1 components in Section III, "Rules for Construction of Nuclear Power Plant Components," of the ASME Code, except as provided in that sectio RG 1.207, Page 2Specifically, the ASME Class 1 requirements contain provisions, including fatigue design curves,for determining a component's suitability for cyclic servic These fatigue design curves are based on strain-controlled tests performed on small polished specimens, at room temperature, in air environment Thus, these curves do not address the impact of the reactor coolant system environment on the componentsof the reactor coolant pressure boundary.This regulatory guide provides guidance for use in determining the acceptable fatigue lifeof ASME pressure boundary components, with consideration of the light-water reactor (LWR) environment. In so doing, this guide describes a method that the staff of the U.S. Nuclear Regulatory Commission (NRC) considers acceptable to support reviews of applications that the agency expects to receive for new nuclear reactor construction permits or operating licenses under 10 CFR Part 50; design certificationsunder 10 CFR Part 52, "Early Site Permits; Standard Design Certifications; and Combined Licenses for Nuclear Power Plants" (Ref. 3); and combined licenses under 10 CFR Part 52 that do not reference a standard desig Because of significant conservatism in quantifying other plant-related variables (such as cyclic behavior, including stress and loading rates) involved in cumulative fatigue life calculations,the design of the current fleet of reactors is satisfactory.This regulatory guide contains information collections that are covered by the requirementsof 10 CFR Parts 50 and 52, which the Office of Management and Budget (OMB) approved under OMB control numbers 3150-0011 and 3150-0151, respectivel The NRC may neither conduct nor sponsor, and a person is not required to respond to, an information collection request or requirement unless the requesting document displays a currently valid OMB control numbe DISCUSSIONThe ASME Section III design curves (Ref. 2), developed in the late 1960s and early 1970s,are based on tests conducted in laboratory air environments at ambient temperature The original code developers applied a margin of 2 on strain and a margin of 20 on cyclic life to account for variations in materials, surface finish, data scatter, and environmental effects (including temperature differences between specimen test conditions and reactor operating experience). However, the developers lacked sufficient data to explicitly evaluate and account for the degradation attributable to exposure to aqueous coolant More recent fatigue test data from the United States, Japan, and elsewhere show that the LWRenvironment can have a significant impact on the fatigue life of carbon and low-alloy steels, austeniticstainless steel, and nickel-chromium-iron (Ni-Cr-Fe) alloys.The staff evaluated two distinct methods for incorporating LWR environmental effectsinto the fatigue analysis of ASME Class 1 component The first method involves developing new fatigue curves that are applicable to LWR environment Given that the fatigue life of ASME Class 1components in LWR environments is a function of several parameters, this method necessitates the development of several fatigue curves to address potential parameter variation Alternatively, a single bounding fatigue curve could be developed, but this approach might be overly conservativefor most application The second method involves using an environmental correction factor (Fen)to account for LWR environments by correcting the fatigue usage calculated with the ASME "air" curves. This method affords the designer greater flexibility to calculate the appropriate impacts for specific environmental parameter RG 1.207, Page 3The NRC staff has selected the Fen method as an acceptable method to properly incorporatethe LWR environmental effects into fatigue analyses of ASME Class 1 component The Fen methodis presented in NUREG/CR-6909, "Effect of LWR Coolant Environments on the Fatigue Life of ReactorMaterials" (Ref. 4). In particular, Appendix A to that report, "Incorporating Environmental Effects into Fatigue Evaluations," describes a method that the staff considers acceptable to incorporate the effectsof reactor coolant environments on fatigue usage factor evaluations of metal component In addition, NUREG/CR-6909 provides a comprehensive review of, and technical basis for, the method described in this regulatory guide, including analyses of each parameter affecting the fatigue evaluation In developing the underlying models, researchers from Argonne National Laboratory (ANL) analyzed existing data to predict fatigue lives as a function of temperature, strain rate, dissolved oxygen level in water, and sulfur content of the stee The resultant method postulates a strain threshold, below whichenvironmental effects on fatigue life do not occu By definition, Fen is the ratio of fatigue lifeof the component material in a room temperature air environment to its fatigue life in LWR coolant at operating temperatur To incorporate environmental effects into the fatigue evaluation, the fatigue usage is calculated using provisions set forth in Section III of the ASME Code, and the fatigue design curve is multiplied by the correction factor.The staff also reviewed the nonconservatism of the current ASME Code design curve in respect tothe existing fatigue data for austenitic stainless steel Recent evaluations of stainless steel test data indicate that the ASME curve is inconsistent with the appropriate test materials and conduct of the fatigue tes Consequently, through this regulatory guide, the NRC staff endorses a new stainless steel air design curv Section 5.1.8 of NUREG/CR-6909 (Ref. 4) provides a comprehensive review of, and technical basis for, that new design curv The Fen defined for stainless steelin NUREG/CR-6909 should be used in conjunction with the new stainless steel air design curve when evaluating the fatigue usage of ASME Class 1 components.In addition, the staff evaluated the incorporation of the Fen method in fatigue analysesfor Ni-Cr-Fe alloys (e.g., Alloy 600 and 690) and weld Section 6 of NUREG/CR-6909 (Ref. 4) discussesthe technical basis for incorporating the environmental effects on nickel alloys and weld In summary, fatigue evaluations for Ni-Cr-Fe alloys are based on the fatigue design curve for austenitic stainless steels. However, the existing fatigue data for Ni-Cr-Fe alloys and their welds are not consistent with the currentASME Code fatigue design curve for austenitic stainless steel The data are either comparable or slightly conservative with the updated ANL model for austenitic stainless steel Thus, the new fatigue design curve proposed for austenitic stainless steels adequately represents the fatigue behavior of Ni-Cr-Fe alloys and their weld Therefore, the new design curve for austenitic stainless steels may also be used for Ni-Cr-Fe alloys and their welds, and the staff finds it acceptable to use the new austenitic stainless steels air design curve in Ni-Cr-Fe alloys environmental fatigue evaluation Consequently, Section 6 of NUREG/CR-6909 presents the respective Fen equations to be usedfor Ni-Cr-Fe alloys and their welds.Section 7 of NUREG/CR-6909 (Ref. 4) evaluates the ASME design curve margin In conductingthat evaluation, the researchers reviewed data available in the literature to assess the subfactors (excluding environment) that are necessary to account for the effects of various uncertainties and differencesbetween actual components and laboratory test specimen The researchers also performed statistical analyses using Monte Carlo simulations to develop fatigue design curves, using the "95/95 criterion."
In other words, the curves should provide 95% confidence that the fatigue life of 95% of the population will be greater than that predicted by the design curve The NRC deems this criterion acceptable because the fatigue design curves are based on crack initiation, rather than component failure and, therefore, additional margin exists between crack initiation and actual component failur RG 1.207, Page 4The results of the Monte Carlo simulations indicate that for both carbon and low-alloy steelsand austenitic stainless steels, the current ASME Code procedure of adjusting the mean test data by a factor of 20 for cyclic life is conservative compared to the 95/95 criterio The results also indicatethat a minimum factor of 12 for cyclic life of both carbon and low-alloy steels and austenitic stainless steels will satisfy the 95/95 criterio Figures 9, 10, and 37 of NUREG/CR-6909 (Ref. 4) present the resultant new air design curves, using margins of 12 for cyclic life and 2 for stress, for carbon steel, low-alloy steel, and austenitic stainless steel, respectivel This regulatory guide uses these new air design curves; thus, an applicant that chooses to adopt the procedure discussed in this guide to determine the fatigue life of stainless steels should use these air design curve However, the existingASME air design curves for carbon and low-alloy steels may also be used with the procedure in this guideto determine the fatigue life of those materials, since their use will yield conservative results.The NRC reviewed and found acceptable several methods for calculating Fe Only the typesof stress cycles or load set pairs that exceed strain threshold criteria for carbon and low-alloy steels, austenitic stainless steel, and Ni-Cr-Fe alloys need to be considered for Fen calculation The evaluationoptions depend on the complexity of the analyzed transient condition and the detail of the evaluatio For example, in an evaluation in which the results of detailed transient analyses are available to determine the necessary parameters (strain rate, temperature, and others), the "modified rate approach"(presented and referenced in Section 4.2.14 of NUREG/CR-6909, Ref. 4) is an acceptable method for determining the Fen value This method involves a strain-based integral for evaluating conditionsfor which temperature and strain rate change, resulting in the variation of Fen over tim This detailedapproach calculates the Fen values based on the strain history for each load set in the fatigue analysisevaluation, considering the effects of strain rate and temperature variations for each incremental segmentin the strain histor Such results may be used to reduce the conservatism in the calculated Fen values. For a simplified calculation yielding a more conservative result for a complex or poorly defined set of transients, the temperature is equal to the average temperature in the transient or segmen The calculated Fen values are then used to incorporate environmental effects into ASME fatigueusage factor evaluation RG 1.207, Page 5 REGULATORY POSITIONThis section describes the methods that the staff considers acceptable for use in performingfatigue evaluations, considering the effects of LWR environments on carbon and low-alloy steels, austenitic stainless steels, and Ni-Cr-Fe alloy Specifically, these methods include calculating the fatigueusage in air using ASME Code analysis procedures, and then employing the environmental correction factor (Fen), as described in NUREG/CR-6909 (Ref. 4). In particular, Appendix A to that reportincludes detailed descriptions and additional guidance concerning the overall method and all the requiredcalculations.1.Carbon and Low-Alloy SteelsThe following procedure should be used to calculate the environmental fatigue usage of carbonand low-alloy steel components in LWR environments.1.1Fatigue Usage in AirCalculate the fatigue usage in air using ASME Code analysis procedures and the fatigue aircurves provided in NUREG/CR-6909, Appendix A, Figures A.1 and A.2 (updated ANL model curves).1.2Environmental Correction Factor (Fen)Calculate the environmental correction factor, Fen, using Equation A.2 of NUREG/CR-6909for carbon steels, or Equation A.3 of NUREG/CR-6909 for low-alloy steel Equations A.4 through A.7 of NUREG/CR-6909 should be used to calculate the parameters used in Equations A.2 and Equation A.8 of NUREG/CR-6909 defines the strain threshold.1.3Environmental Fatigue UsageCalculate the environmental fatigue usage using Equation A.20 of NUREG/CR-6909.2.Austenitic Stainless SteelsThe following procedure should be used to calculate the environmental fatigue usageof austenitic stainless steel components in LWR environments.2.1Fatigue Usage in AirCalculate the fatigue usage in air using ASME Code analysis procedures and the new stainlesssteel fatigue air curve provided in NUREG/CR-6909, Appendix A, Figure A.3 (proposed design curve).2.2Environmental Correction Factor (Fen)For all types of austenitic stainless steels (e.g., Types 304, 310, 316, 347, and 348), calculate Fenusing Equation A.9 of NUREG/CR-690 Equations A.10 through A.12 of NUREG/CR-6909 should beused to calculate the parameters used in Equation Equation A.13 of NUREG/CR-6909 defines the strain threshold.2.3Environmental Fatigue UsageCalculate the environmental fatigue usage using Equation A.20 of NUREG/CR-690 RG 1.207, Page 63.Ni-Cr-Fe AlloysThe following procedure should be used to calculate the environmental fatigue usagefor Ni-Cr-Fe alloy components in LWR environments (e.g., Alloy 600 and 690).3.1Fatigue Usage in AirCalculate the fatigue usage in air using ASME Code analysis procedures and the new stainlesssteel fatigue air curve provided in NUREG/CR-6909, Appendix A, Figure A.3 (proposed design curve).3.2Environmental Correction Factor (Fen)For all types of Ni-Cr-Fe alloys (e.g., Alloy 600 and 690), calculate Fen using Equation A.14of NUREG/CR-690 Equations A.15 through A.17 of NUREG/CR-6909 should be used to calculate the parameters used in Equation A.1 Equation A.18 of NUREG/CR-6909 defines the strain threshold.3.3Environmental Fatigue UsageCalculate the environmental fatigue usage using Equation A.20 of NUREG/CR-690 IMPLEMENTATIONThe purpose of this section is to provide information to applicants and licensees regardingthe NRC staff's plans for using this regulatory guid This regulatory guide only applies to new plants, and no backfitting is intended or approved in connection with its issuance.Except in those cases in which an applicant or licensee proposes or has previously establishedan acceptable alternative method for complying with specified portions of the NRC's regulations, the methods described in this guide will be used in evaluating submittals in connection with applicationsfor construction permits, standard plant design certifications, operating licenses, early site permits, and combined licenses.REGULATORY ANALYSIS / BACKFIT ANALYSISThe regulatory analysis and backfit analysis for this regulatory guide are available in DraftRegulatory Guide DG-1144, "Guidelines for Evaluating Fatigue Analyses Incorporating the Life Reduction of Metal Components Due to the Effects of the Light-Water Environment in New Reactors" (Ref. 5). The NRC issued DG-1144 in July 2006 to solicit public comment on the draft of this Regulatory Guide 1.20 All NRC regulations listed herein are available electronically through the Electronic Reading Room on the NRC'spublic Web site, at http://www.nrc.gov/reading-rm/doc-collections/cfr/. Copies are also available for inspectionor copying for a fee from the NRC's Public Document Room at 11555 Rockville Pike, Rockville, Maryland; the PDR's mailing address is USNRC PDR, Washington, DC 20555; telephone (301) 415-4737 or (800) 397-4209; fax (301) 415-3548; email PDR@nrc.gov.2Copies may be purchased from the American Society of Mechanical Engineers, Three Park Avenue, NewYork, NY 10016-5990; phone (212) 591-8500; fax (212) 591-8501; www.asme.org.3Copies are available at current rates from the U.S. Government Printing Office, P.O. Box 37082, Washington, DC20402-9328 (telephone 202-512-1800); or from the National Technical Information Service (NTIS) by writing NTIS at 5285 Port Royal Road, Springfield, Virginia 22161, online at http://www.ntis.gov, by telephone at (800) 553-NTIS(6847) or (703)605-6000, or by fax to (703) 605-690 Copies are also available for inspection or copying for a fee from the NRC's Public Document Room (PDR), which is located at 11555 Rockville Pike, Rockville, Maryland; the PDR's mailing address is USNRC PDR, Washington, DC 20555-000 The PDR can also be reached by telephone at (301) 415-4737 or (800)397-4209, by fax at (301)415-3548, and by email to PDR@nrc.go NUREG/CR-6909is also available through the NRC's Agencywide Documents Access and Management System (ADAMS)
at http://www.nrc.gov/reading-rm/adams.html, under Accession #ML070660620.4Draft Regulatory Guide DG-1144 is available electronically under Accession #ML060970173 in the NRC'sAgencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html. Copies are also available for inspection or copying for a fee from the NRC's Public Document Room (PDR), which is located at 11555 Rockville Pike, Rockville Maryland; the PDR's mailing address is USNRC PDR, Washington, DC 20555-000 The PDR can also be reached by telephone at (301) 415-4737 or (800) 397-4209, by fax at (301) 415-3548,and by email to PDR@nrc.gov.RG 1.207, Page 7REFERENCES1.U.S. Code of Federal Regulations, Title 10, Energy, Part 50, "Domestic Licensing of Productionand Utilization Facilities," U.S. Nuclear Regulatory Commission, Washington, DC.12.ASME Boiler and Pressure Vessel Code,Section III, "Rules for Construction of Nuclear PowerPlant Components," American Society of Mechanical Engineers, New York, NY, 1992.23.U.S. Code of Federal Regulations, Title 10, Energy, Part 52, "Early Site Permits; StandardDesign Certifications; and Combined Licenses for Nuclear Power Plants," U.S. Nuclear Regulatory Commission, Washington, DC.14.NUREG/CR-6909, "Effect of LWR Coolant Environments on Fatigue Life of Reactor Materials"(Final Report), ANL-06/08, U.S. Nuclear Regulatory Commission, Washington, DC, February 2007.35.Draft Regulatory Guide DG-1144, "Guidelines for Evaluating Fatigue Analyses Incorporatingthe Life Reduction of Metal Components Due to the Effects of the Light-Water Reactor Environment for New Reactors," U.S. Nuclear Regulatory Commission, Washington, DC, July 2006.4