ML13120A180
| ML13120A180 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 05/29/2013 |
| From: | Jessie Quichocho Plant Licensing Branch II |
| To: | James Shea Tennessee Valley Authority |
| Saba F NRR/DORL/LPL2-2 | |
| References | |
| TAC ME8779 | |
| Download: ML13120A180 (8) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 May 29,2013 Mr. Joseph W. Shea Corporate Manager - Nuclear Licensing Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801
SUBJECT:
BROWNS FERRY NUCLEAR PLANT, UNIT 2 - RELIEF REQUEST RR 2-ISI-28, FOR THE THIRD 10-YEAR INSERVICE INPSECTION INTERVAL (TAC NO. ME8779)
Dear Mr. Shea:
By letter dated May 24,2012, as supplemented on February 27,2013, the Tennessee Valley Authority (TVA, the licensee) submitted a request for relief from weld examination coverage requirements specified in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (ASME Code),Section XI for the reactor pressure vessel nozzle at Browns Ferry Nuclear Plant (BFN) Unit 2. This relief request (RR) was requested for the BFN Unit 2 Third 10-Year Inspection Interval (lSI).
Specifically, pursuant to Title 10 of Code of Federal Regulations (10 CFR)
Section SO.SSa(g)(S)(iii), TVA requested relief from weld examination coverage requirements specified in the ASME Code,Section XI, for one reactor pressure vessel nozzle-to-vessel (head) full penetration weld and nozzle inside radius section due to access limitations caused by design. Ultrasonic examinations were performed on the accessible areas of this weld to the maximum extent practical given the design configuration of the weld.
The U.S. Nuclear Regulatory Commission (NRC) staff, based on review of your submittals, has concluded that the ASME Code examination coverage requirements for the welds in RR 2-ISI-28 are impractical; however, the NRC staff finds that the proposed alternative provides reasonable assurance of structural integrity. The NRC staff has determined that granting RR 2-ISI-28, pursuant to Title 10 of Code of Federal Regulations (10 CFR)
Section SO.SSa(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in the subject request for relief remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
J. Shea -2 This relief is granted and the proposed alternative by TVA is authorized for the third 10-year lSI interval at BFN Unit 2, which began May 25, 2001 and ended May 24, 2011.
If you have any questions regarding this matter, please contact the Senior Project Manager, Ms. Farideh Saba at (301) 415-1447 or via e-mail at Farideh.Saba@nrc.gov.
Sincerely, Docket No. 50-260
Enclosure:
Safety Evaluation cc w/enclosure: Distribution via Listserv
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION THIRD 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN REQUEST FOR RELIEF NO. 2-ISI-28 TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNIT 2 DOCKET NUMBER: 50-260
1.0 INTRODUCTION
By letter dated May 24,2012 (Agency Wide Document Access and Management System (ADAMS) Accession No. ML ML12150A367), as supplemented on February 27,2013 (ADAMS Accession No. ML13063A018), the Tennessee Valley Authority (TVA, the licensee) submitted a request for relief from weld examination coverage requirements specified in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (ASME Code),
Section XI. In accordance with Title 10 of Code of Federal Regulations (10 CFR),
Section 50.55a(g)(5)(iii), TVA requested relief from weld examination coverage requirements specified in the ASME Code,Section XI, for one reactor pressure vessel nozzle-to-vessel (head) full penetration weld and nozzle inside radius section due to access limitations caused by design. This relief request (RR) was requested for the Browns Ferry Nuclear Plant (BFN) Unit 2 Third 10-Year Inspection Interval (lSI), which began May 25, 2001, and ended May 24, 2011.
Additionally, in response to the Nuclear Regulatory Commission (NRC, Commission) staff Request for Additional Information (RAI) dated November 2,2012 (ADAMS Accession No. ML12306A352), the licensee provided additional information in its letter dated February 27, 2013 (ADAMS Accession No. ML13063A018).
2.0 REGULATORY EVALUATION
Inservice inspection of ASME Code Class 1, 2, and 3 components is performed in accordance with Section XI of the ASME Code and applicable addenda, as required by 10 CFR 50.55a(g),
except where specific relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). Regulation 10 CFR 50.55a(a)(3) states, in part, that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if the applicant demonstrates that: (i) the proposed alternatives would provide an acceptable level of quality and safety or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Enclosure
- 2 Pursuant to 10 CFR SO.SSa(g)(4), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the desjgn and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year lSI interval and subsequent lSI intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR SO.SSa(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The ASME Code of Record for the BFN, Unit 2 third 10-year lSI interval is the 1995 Edition through the 1996 Addenda of the ASME Boiler and Pressure Vessel Code.
Section SO.SSa(b)(2)(xv), "Appendix VIII specimen set and qualification requirements," states, in part, that licensees using Appendix VIII in the 1995 Edition through the 2001 Edition of the ASME Boiler and Pressure Vessel Code may elect to comply with all of the provisions in paragraphs (b)(2)(xv)(A) through (b)(2)(xv)(M), except for paragraph (b)(2)(xv)(F), which may be used at the licensee's option.
Finally, with respect to examination coverage, "essentially 100 percent" is clarified by ASME Code Case N-460, "Alternative Examination Coverage for Class 1 and Class 2 Welds," to be greater than 90 percent coverage of the examination volume, or surface area, as applicable.
ASME Code Case N-460 has been approved for use by the NRC in Regulatory Guide 1.147, Revision 16, "Inservice Inspection Code Case Acceptability."
3.0 TECHNICAL EVALUATION
3.1 The Licensee's Relief Request Code Requirement ASME Code,Section XI, "Rules for Inservice Inspection Nuclear Power Plant Components,"
1995 Edition through the 1996 Addenda, Table IWB-2S00-1, Category B-D. "Full Penetration Welded Nozzles in Vessels - Inspection Program B," Item No. B3.90, "Nozzle-to-Vessel Welds" requires volumetric examination of 100 percent of the weld and adjacent base material as depicted in Figure IWB-2S00-7(a). Item No. B3.100, "Nozzle Inside Radius Section" requires a volumetric examination of the inside radius sections of nozzles in vessels as depicted in Figure IWB-2S00-7(a).
For ultrasonic examination techniques, the licensee elected to use procedures. equipment, and personnel qualified to the requirements of the Performance Demonstration Initiative (POI)
Program, consistent with the requirements of the 2001 Edition of the ASME Code,Section XI, in accordance with 10 CFR SO.SSa(b)(2)(xxiv) and, as amended by Sections 10 CFR SO.SSa(b)(2)(xv)(B) through 10 CFR SO.SSa(b)(2)(xv)(G), and 10 CFR 10.SSa(b)(2)(xvi)(A).
- 3 Component Identification Component: Reactor Pressure Vessel Nozzle N-10, Standby Liquid Control (SLC) Nozzle.
Weld: Nozzle-to-vessel weld N10-NV.Section: Nozzle inside radius section N10-1R.
Licensee's Code Relief Request: (as stated)
Relief is requested from the requirement of ASME Section XI Code, Table IWB-2500-1, Examination Category B-D, Item Nos. B3.90 and B3.1 00 to perform essentially 100 percent volumetric examination of the weld and adjacent base material.
Licensee's Basis for Requesting Relief (as stated)
The approximately 2-inch SLC nozzle is designed with an integral socket to which the boron injection piping is welded. The SLC nozzle is located in the bottom head of the reactor pressure vessel (RPV) in an area that is inaccessible for examination from inside of the vessel. The design configuration of the RPV nozzle-to-vessel weld (N10-NV) area precludes an ultrasonic test (UT) examination of essentially 100 percent of the required volume. The component design configuration limits UT examination coverage of the weld to the percentages listed in the table of the enclosure to the May 24, 2012, letter.
Licensee's Proposed Alternative Examination (as stated)
In lieu of the ASME Code required essentially 100 percent volume UT examination on the nozzle-to-vessel weld and inside radius section, the licensee proposes a UT examination of accessible areas to the maximum extent practical given the component design configuration of the RPV nozzle-to-vessel weld.
3.2 NRC Staff Evaluation Nozzle-to-Vessel Welds ASME Code,Section XI, "Rules for Inservice Inspection Nuclear Power Plant Components,"
1995 Edition through the 1996 Addenda, Table IWB-2500-1. Category B-D. "Full Penetration Welds of Nozzles in Vessels," Item No. B3.90,"Nozzle-to-Vessel Welds" requires volumetric examination of 100 percent of the weld and adjacent base material.
The design configuration of SLC nozzle-to-vessel weld precludes an ultrasonic examination of essentially 100 percent of the required volume. The component design configuration limits UT examination coverage of the weld to 81.7 percent coverage (licensee response to RAI 8 in the February 27,2013, letter). In order to examine the weld in accordance with the Code requirements. the RPV would require extensive design modifications. The physical arrangement of the SLC nozzle-to-vessel weld precludes UT examination from the nozzle side.
The limitations are inherent to the barrel-type nozzle-to-vessel weld design configuration. In response to the NRC staff's RAI 3, the licensee specifically indicated that the limitations are due to the radius of curvature in the transition area between the nozzle and the vessel shell, and geometric design configurations limiting access to a single side of the weld. In order to meet the Code requirements, the nozzle and/or vessel would have to be modified to facilitate access for
-4 UT search units. In addition, the SLC nozzle is located in the bottom head of the RPV in an area that is inaccessible for examination from inside of the vessel. Therefore, the examination must be performed only from the outside surface.
Previous examinations of the SLC nozzle were completed during the BFN, Unit 2 First 10-Year lSI Interval (March 1,1975 to May 24,1992) and the Second 10-Year lSI Interval (May 24,1992 to May 24,2001). The Third 10-Year lSI Interval examination utilized the latest ultrasonic techniques, procedures, equipment, and personnel qualified to the requirements of the POI Program, in the 2001 Edition of Section XI of the ASME Code, in accordance with 10 CFR 50.55a(b)(2)(xxiv) and, as amended by Sections 50.55a(b)(2)(xv)(B) through 50.55a(b)(2)(xv)(G), and 50.55a(b)(2)(xvi)(A), by following the Electric Power Research Institute's POI processes. Therefore, the percentage of examination coverage obtained in the third interval (81.7 percent coverage) was larger than the coverage reported for the second interval in RR 2-ISI-6 Revision 2 (56 percent coverage). No recordable indication was identified during the inspections of Weld N10-NV.
Radiographic examination as an alternate volumetric examination method was determined to be impractical due the radiological concerns and accessibility to the inside surface of the RPV to place radiographic film.
Based on the foregoing. the NRC staff determined that the ASME Code requirements are impractical for the SLC nozzle-to-vessel weld. The staff determined, based on the volumetric coverage obtained for the nozzle-to-vessel weld, that it is reasonable to conclude that if significant service-induced degradation had occurred in the nozzle-to-vessel weld, evidence of degradation would have been detected. Furthermore, the staff determined that the examinations performed provide reasonable assurance of structural integrity of the nozzle-to vessel weld of the SLC nozzle for BFNP, Unit 2.
In addition, the SLC nozzle received a visual (VT-2) examination in conjunction with the Class I System Leakage Test conducted during each refueling outage of the Third 10-Year lSI Interval.
BFNP Unit 2 refueled five times during the Third 10-Year lSI Interval. Consequently, the SLC nozzle underwent five VT-2 examinations during the Third 10-Year lSI Interval. No leakage was identified during the VT-2 examinations of the SLC nozzle. The VT-2 visual examinations of the nozzle area, which will continue to be performed during each refueling outage in conjunction with the ASME Code, Class 1 System Leakage Test, will provide reasonable assurance of the leak tightness of the nozzle-to-vessel weld because the system leakage test will provide for detection of flaws when they are small and can be repaired prior to the SLC nozzle losing its ability to perform its intended function.
Nozzle Inside Radius Section ASME Code Section XI, "Rules for Inservice Inspection Nuclear Power Plant Components,"
1995 Edition through the 1996 Addenda, Table IWB-2500-1, Category B-O, "Full Penetration Welds of Nozzles in Vessels," Item No. B3.100, "Nozzle Inside Radius Section" requires a volumetric examination of the inside radius sections of nozzles in vessels.
Relief is requested from the requirement to perform the volumetric examination of the inside radius section of the SLC nozzle. The design configuration of SLC nozzle-to-vessel weld precludes an ultrasonic examination of essentially 100 percent of the inside corner radius. The
- S component design configuration limits UT examination coverage of the inside surface to 90 percent coverage (table of the enclosure to the May 24, 2012 letter). The staff determined that the licensee provided valid technical arguments that support their assertion that volumetric examination of the inside radius section of the SLC nozzle is not feasible and that the design of the SLC nozzle precludes high cycle fatigue resulting from thermal stratification.
Based on the foregoing, the staff determined that the ASME Code requirements are impractical for the SLC nozzle inner radius section. The staff determined, based on the volumetric coverage obtained, that it is reasonable to conclude that if significant service-induced degradation had occurred in the inner radius section of the SLC nozzle, evidence of degradation would have been detected. Furthermore, the staff determined that the examinations performed provide reasonable assurance of structural integrity of the inner radius of the SLC nozzle for BFN, Unit 2 because there were no recordable indications identified during the Third 10-Year lSI Interval inspection of inside radius section N10-1R.
As discussed previously, the SLC nozzle receives VT-2 examinations in conjunction with the Class I System Leakage Test conducted during each refueling outage, and the SLC nozzle underwent five VT-2 examinations during the Third 10-Year lSI Interval that did not identify any leakage. Continued performance of the VT-2 visual examinations of the SLC nozzle will provide reasonable assurance of the leak tightness of the nozzle inner radius section because the system leakage test will provide for detection of flaws when they are small and can be repaired prior to the SLC nozzle losing its ability to perform its intended function.
4.0 CONCLUSION
As set forth above, the NRC staff has determined that granting relief pursuant to 10 CFR SO.SSa(g)(6)(i) is authorized by law and will not endanger life or property, or the common defense and security, and is otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
Furthermore, the staff concluded that the examinations performed to the extent practical provide reasonable assurance of structural integrity of the SLC nozzle. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR SO.SSa(g)(6)(i). Therefore, the NRC staff grants relief for the subject examinations of the SLC nozzle contained in RR No. 2-ISI-28 for the BFN, Unit 2 Third 10-Year lSI Interval.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in the subject request for relief remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: Gary L. Stevens Jeffrey C. Poehler Date: May 29, 2013
J. Shea -2 This relief is granted and the proposed alternative by TVA is authorized for the third 10-year lSI interval at BFN Unit 2, which began May 25, 2001 and ended May 24, 2011.
If you have any questions regarding this matter, please contact the Senior Project Manager, Ms. Farideh Saba at (301) 415-1447 or via e-mail at Farideh.Saba@nrc.gov.
Sincerely, IRA!
Jessie F. Quichocho, Chief Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-260
Enclosure:
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PUBLIC LPL2-2 RlF RidsNrrDorlLpl2-2 RidsNrrPMBrownsFerry DHuyck SCumblidge, NRR RidsNrrLABClayton RidsNrrDeEvib RidsAcrsAcnw_MailCTR RidsRgn2MailCenter GStevens, NRR RidsNrrLAKGoldstein ADAMS Accession No. ML13120A180 *b e-mail OFFICE LPL2-2/PM LPL2-2/LA EVIB/BC* LPL2-2/BC
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NAME FSaba SRosenberg JQuichocho DATE OS/28/13 OS/23/13 05/29/13