RIS 2008-10, 2008/04/11-Vermont Yankee July 2008 Evidentiary Hearing - Intervenor Exhibit NEC-JH 23, Nrc, NRC Regulatory Issue Summary 2008-10 Fatigue Analysis of Nuclear Power Plan Components (April 11, 2008)

Fatigue Analysis of Nuclear Power Plant Components

ML080950235
Person / Time
Issue date:	04/11/2008
Revision:	0
From:	Case M J NRC/NRR/ADRO/DPR
To:
Chang, K, NRR/DLR/RLRC, 415-1198
References
RIS-08-XXX
Download: ML080950235 (4)

See also: RIS 2008-10

Text

April 11, 2008

DRAFT NRC REGULATORY ISSUE SUMMARY 2008-XX FATIGUE ANALYSIS OF NUCLEAR POWER PLANT COMPONENTS ADDRESSEES All holders of operating licenses for nuclear power reactors, except those who have permanently ceased operations and have certified that fuel has been permanently removed from the reactor vesse INTENT The U.S. Nuclear Regulatory Commission (NRC) is issuing this regulatory issue summary (RIS)

to inform licensees of an analysis methodology used to demonstrate compliance with the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code)

fatigue acceptance criteria that could be nonconservative if not correctly applie BACKGROUND INFORMATION Title 10 of the Code of Federal Regulations (10 CFR) Part 54, "Requirements for Renewal of Operating Licenses for Nuclear Power Plants," requires that applicants for license renewal perform an evaluation of time-limited aging analyses relevant to structures, systems, and components within the scope of license renewa The fatigue analysis of the reactor coolant pressure boundary components is an issue that involves time-limited assumption In addition, the staff has provided guidance in NUREG-1800, Rev. 1, "Standard Review Plan for Review of License Renewal Applications for Nuclear Power Plants," issued September 200 NUREG-1800, Rev. 1, specifies that the effects of the reactor water environment on fatigue life be evaluated for a sample of components to provide assurance that cracking because of fatigue will not occur during the period of extended operatio Since the reactor water environment has a significant impact on the fatigue life of components, many license renewal applicants have performed supplemental detailed analyses to demonstrate acceptable fatigue life for these component CFR 50.55a, "Codes and Standards," specifies the ASME Code requirements for operating reactor Some operating facilities may have performed supplemental detailed analysis of components because of new loading conditions identified after the plant began operatio ML080950235

RIS 2008-XX Page 2 of 4 SUMMARY OF ISSUE The staff identified a concern regarding the methodology used by some license renewal applicants to demonstrate the ability of nuclear power plant components to withstand the cyclic loads associated with plant transient operations for the period of extended operatio This particular analysis methodology involves the use of the Green's function to calculate the fatigue usage during plant transient operations such as startups and shutdown The Green's function approach involves performing a detailed stress analysis of a component to calculate its response to a step change in temperatur This detailed analysis is used to establish an influence function, which is subsequently used to calculate the stresses caused by the actual plant temperature transient This methodology has been used to perform fatigue calculations and as input for on-line fatigue monitoring program The Green's function methodology is not in questio The concern involves a simplified input for applying the Green's function in which only one value of stress is used for the evaluation of the actual plant transients. The detailed stress analysis requires consideration of six stress components, as discussed in ASME Code,Section III, Subsection NB, Subarticle NB-320 Simplification of the analysis to consider only one value of the stress may provide acceptable results for some applications; however, it also requires a great deal of judgment by the analyst to ensure that the simplification still provides a conservative resul The staff has requested that recent license renewal applicants that have used this simplified Green's function methodology perform confirmatory analyses to demonstrate that the simplified Green's function analyses provide acceptable result The confirmatory analyses retain all six stress component To date, the confirmatory analysis of one component, a boiling-water reactor feedwater nozzle, indicated that the simplified input for the Green's function did not produce conservative results in the nozzle bore area when compared to the detailed analysi However, the confirmatory analysis still demonstrated that the nozzle had acceptable fatigue usag Licensees may have also used the simplified Green's function methodology in operating plant fatigue evaluations for the current license ter For plants with renewed licenses, the staff is considering additional regulatory actions if the simplified Green's function methodology was use RIS 2008-XX Page 3 of 4 BACKFIT DISCUSSION This RIS informs addressees of a potential nonconservative calculation methodology and reminds them that the ASME Code fatigue analysis should be performed properl For license renewal, metal fatigue is evaluated as a time-limited aging analysis in accordance with 10 CFR 54.21(c). The associated staff review guidance appears in Section 4.3, "Metal Fatigue Analysis," of NUREG-1800, Rev. For operating reactors, the ASME Code requirements appear in 10 CFR 50.55 This RIS does not impose a new or different regulatory staff positio It requires no action or written response and, therefore, is not a backfit under 10 CFR 50.109, "Backfitting." Consequently, the NRC staff did not perform a backfit analysi FEDERAL REGISTER NOTIFICATION A notice of opportunity for public comment on this RIS was published in the Federal Register (xx FR xxxxx), on { xx, 2008}. Comments were received from {indicate the number of commentors by type}. The staff considered all comment The staff's evaluation of the comments is publicly available through NRC's Agencywide Documents Access and Management System under Accession No. ML #########.

CONGRESSIONAL REVIEW ACT The NRC has determined that this RIS is not a rule as designated by the Congressional Review Act (5 U.S.C. 801-808) and; therefore, is not subject to the Ac PAPERWORK REDUCTION ACT STATEMENT This RIS does not contain information collection requirements that are subject to the requirements of the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et seq.).

Public Protection Notification The NRC may not conduct or sponsor, and a person is not required to respond to, a request for information or an information collection requirement unless the requesting document displays a currently valid Office of Management and Budget control numbe RIS 2008-XX Page 4 of 4 CONTACT Please direct any questions about this matter to the technical contacts listed belo Michael J. Case, Director Division of Policy and Rulemaking Office of Nuclear Reactor Regulation

Technical Contacts: Kenneth C. Chang, NRR John R. Fair, NRR 301-415-1913 301-415-2759 E-mail: kxc2@Nrc.gov E-mail: jrf@nrc.gov Note: The NRC's generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collection RIS 2008-10 Page 4 of 4 CONTACT Please direct any questions about this matter to the technical contacts listed belo Michael J. Case, Director Division of Policy and Rulemaking Office of Nuclear Reactor Regulation

Technical Contacts: Kenneth C. Chang, NRR John R. Fair, NRR 301-415-1913 301-415-2759 E-mail: kxc2@Nrc.gov E-mail: jrf@nrc.gov

Note: NRC's generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collection DISTRIBUTION: RIS R/F NRR_ADES Distribution NRR_ADR ADAMS ACCESSION NO.: ML080950235 OFFICE DE/NRR/EMCB BC/DLR/RER1 TECH EDITOR BC/DE/EMCB AD/NRR/DLR DD/NRR/DE NAME JFair KChang JMedoff for HChang KManoly SLee PHiland DATE 4/7/08 4/7/08 4/08/08 4/7/08 4/8/08 4/09/08 OFFICE DD/NRR/DORL BC/DE/EMB1 BC/DE/EMB2 OE OGC/NLO OGC/CRA NAME CHaney AHsia JDixon-Herrity SMagruder EWilliams SHamrick DATE 4/10/08 4/10/08 4/10/08 4/09/08 4/11/08 4/10/08 OFFICE PMDA/IMT OIS LA/DPR/PGCB DPR/PGCB BC/DPR/PGCB D/DPR NAME LHill TDonnell CHawes AMarkley MMurphy MCase DATE 4/09/08 4/10/08 4/11/08 4/11/08 4/11/08 4/11/08 OFFICIAL RECORD COPY