ML112650071

South Texas Project, Units 1 and 2 - Relief Request RR-ENG-3-05, from Requirements for Ultrasonic Examination of Reactor Pressure Vessel Shell-to-Flange Welds for Third 10-Year Inservice Inspection (TAC Nos. ME4975 and ME4976)

ML112650071
Person / Time
Site:	South Texas
Issue date:	10/14/2011
From:	Markley M T Plant Licensing Branch IV
To:	Halpin E D South Texas
Singal, Balwant, 415-3016, NRR/DORL/LPL4
References
TAC ME4975, TAC ME4976
Download: ML112650071 (8)

Text

UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555*0001 October 14, 2011 Mr. Edward D. President and Chief Executive Chief Nuclear Officer STP Nuclear Operating Company South Texas Project P. O. Box 289 VVadsworth,TX 77483 SOUTH TEXAS PRO ..IECT, UNITS 1 AND 2 -REQUEST FOR RELIEF RR-ENG 05 FROM ASME CODE, SECTION XI REQUIREMENTS FOR ULTRASONIC EXAMINATION OF REACTOR PRESSURE VESSEL SHELL-TO-FLANGE VVELDS (TAC NOS. ME4975 AND ME4976)

Dear Mr. Halpin:

By letter dated October 18,2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 102950166), STP Nuclear Operating Company (the licensee) submitted request RR-ENG 05 in which it requested relief from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI requirements applicable to ultrasonic (UT) examinations to be conducted in accordance with Section XI, Appendix I of the ASME Code, pursuant to paragraph 50.55a(a)(3){i) of Title 10 of the Code of Federal Regulations (10 CFR) for South Texas Project (STP), Units 1 and 2. Article IVVA-2232 of the ASME Code,Section XI, requires that UT examinations be conducted in accordance with Section XI, Appendix I of the ASME Code. Appendix I, Article 1-2110(b) requires that UT examinations of the reactor pressure vessel (RPV) shell-to-flange welds be examined in accordance with ASME Code,Section V, Article 4. The licensee has proposed an alternative using the performance-based methods of ASME Code,Section XI, Appendix VIII, Supplements 4 and 6, as modified by 10 CFR 50.55a(b)(2)(xxiv). The request is for the third 10-year inservice inspection (lSI) interval for STP, which ends on September 25,2020, for Unit 1, and October 19, 2020, for Unit 2. The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the licensee's request and determined that the proposed alternative provides an acceptable level of quality and safety. Based on the enclosed safety evaluation, the NRC staff concludes that procedures, personnel, and equipment qualified in accordance with the ASME Code,Section XI, Appendix VIII, demonstrate a high probability of detecting flaws and increase the reliability of examinations of weld configurations within the scope of the Performance Demonstration Initiative program. Therefore, pursuant to 10 CFR 50.55a(a){3)(i), the NRC staff authorizes the use of the proposed alternative for the third 10-year lSI interval for STP, Units and 2. All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in the subject requests for relief remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

E. Halpin -2 If you have any questions, please contact the project manager, Balwant K. Singal, at 301-415-3016 or via e-mail at Balwant.Singal@nrc.gov. Sincerely, Michael T. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosure:

As stated cc w/encl: Distribution via Listserv UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF FROM ASME SECTION XI CODE REQUIREMENTS FOR ULTRASONIC EXAMINATION OF REACTOR PRESSURE VESSEL SHELL-TO-FLANGE WELDS THIRD 10-YEAR INSERVICE INSPECTION INTERVAL STP NUCLEAR OPERATING COMPANY SOUTH TEXAS PROJECT, UNITS 1 AND 2 DOCKET NOS. 50-498 AND 50-499

1.0 INTRODUCTION

By letter dated October 18, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 102950166), STP Nuclear Operating Company (the licensee) submitted a request for relief (RR-ENG 05) from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI requirements from ultrasonic (UT) examinations to be conducted in accordance with Section XI, Appendix I of the ASME Code pursuant to paragraph 50.55a{a)(3)(i) of Title 10 of the Code of Federal Regulations (10 CFR) for South Texas Project (STP), Units 1 and 2. Article IWA-2232 of the ASME Code,Section XI, requires that UT examinations be conducted in accordance with Section XI, Appendix I of the ASME Code. Appendix I, Article 1-2110(b) requires that UT examinations of the reactor pressure vessel (RPV) shell-to-flange welds be examined in accordance with ASME Code,Section V, Article 4. The licensee has proposed an alternative using the performance-based methods of ASME Code,Section XI, Appendix VIII, Supplements 4 and 6, as modified by 10 CFR 50.55a(b)(2)(xxiv). The request is for the third 10-year inservice inspection (lSI) interval for STP, which ends on September 25,2020, for Unit 1, and October 19, 2020, for Unit 2.

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 U.S. Nuclear Regulatory Commission (NRC) pursuant to 10 CFR 50.55a(g)(6)(i). The regulations in 10 CFR 50.55a(a)(3) state that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if: Enclosure

-2 (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. Pursuant to 10 CFR SO.SSa(g)(4), ASME Code Class 1,2, and 3 components (including supports) shall meet the requirements, except the design 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 regulation requires that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent 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 applicable Code of record for the third 10-year interval lSI program at STP, Units 1 and 2 is the 2004 Edition of the ASME Code,Section XI, without Addenda.

3.0 TECHNICAL EVALUATION

3.1 Component Identification RR-ENG 0S addresses the ASME Code Class 1, Examination Category B-A, Item No. B1.30 RPV shell-to-flange welds at STP, Units 1 and 2. 3.2 Code Requirements The 2004 Edition of the ASME Code,Section XI, IWA-2232 requires that UT examinations be conducted in accordance with the ASME Code,Section XI, Appendix I. Appendix I, 1-2110(b) requires UT examinations of RPV shell-to-flange welds to be conducted in accordance with the ASME Code,Section V, Article 4. Appendix I, 1-211 O(b) also requires that these examinations be further supplemented by Appendix I, Table 1-2000-1. The required examination volume for RPV shell-to-flange welds is provided in the ASME Code,Section XI, Figure IWB-2S00-4, as specified in the ASME Code,Section XI, Table IWB-2S00-1 for these Examination Category B-A Item No. 81.30 welds. 3.3 Basis for Relief and Proposed Alternative (as stated by the licensee) The RPV shell-to-flange weld is the only circumferential shell weld in the RPV not examined according to ASME [Code,] Section XI, Appendix VIII, Supplements 4 and 6 UT techniques [Article 1-2110(a)]. Procedures, equipment, and personnel qualified by the Appendix VIII Performance Demonstration Initiative (PDI) Programs for Supplements 4 and 6 have demonstrated a high probability of detecting flaws, and are generally considered superior to those qualified under the [ASME Code,] Section V, Article 4 criteria.

-3.4 Proposed Alternative and Basis for Relief (as stated by the licensee) The RPV shell-to-flange weld will be examined in accordance with the performance-based methods of ASME [Code,] Section XI, 2001 Edition (no Addenda), Appendix VIII, Supplements 4 and 6, as modified by 10 CFR SO. SSa(b )(2)(xxiv). ASME [Code,] Section XI, 2004 Edition 200S Addenda, Appendix I, Article 2600(a) states that for components to which Appendix VIII is not applicable, examination procedures, personnel, and equipment qualified in accordance with Appendix VIII may be applied, provided such components, materials, sizes, and shapes are within the scope of the qualified examination procedure. Industry experience has shown that the Appendix VIII PDI approach for UT examinations equals or surpasses the UT examination techniques of the ASME Code,Section V, Article 4 for detection and characterization of flaws in reactor pressure vessels. The procedure requires the examiner to evaluate all indications determined to be flaws regardless of their amplitude. The proposed qualification approach is more conservative. Therefore, the use of the proposed alternative will provide an acceptable level of quality and safety. 3.S NRC Staff Evaluation The 2004 Edition of the ASME Code,Section XI, IWA-2232 states that UT examinations shall be conducted in accordance with the ASME Code,Section XI, Appendix I. Appendix I, 1-2110(b) states that UT examination of RPV shell-to-flange welds, closure head-to-flange welds, and integral attachment welds shall be conducted in accordance with the ASME Code,Section V, Article 4, as supplemented by Appendix I, Table 1-2000-1. The ASME Code,Section V, Article 4 provides a prescriptive process for qualifying UT examination procedures and the scanning requirements for examinations. UT examinations performed in accordance with the ASME Code,Section V, Article 4 use detailed criteria for setting up and calibrating equipment, calculating coverage, and detecting indications. The capability of an ASME Code,Section V, Article 4 UT examination is demonstrated with calibration blocks made from representative material containing holes and notches. In lieu of the ASME Code,Section V, Article 4 angle-beam UT examination requirements, the licensee proposed to perform the RPV shell-to-flange weld examination at STP, Units 1 and 2, using examination procedures, personnel, and equipment qualified in accordance with the ASME Code,Section XI, Appendix VIII, Supplements 4 and 6, as modified by 10 CFR SO.SSa(b)(2)(xxiv). The regulations in 10 CFR SO.SSa(b)(2)(xxiv) limit the use ofthe ASME Code,Section XI, Appendix VIII to the 2001 Edition of the ASME Code with no Addenda. The ASME Code,Section XI, Appendix VIII is a performance-based UT examination method. Performance-based UT examination requires that detailed criteria be used for performance demonstration tests. The results for the tests are compared against statistically developed screening criteria. The tests are performed on representative mockups containing flaws similar to those found in operating plants. The performance-based tests demonstrate the of UT examination procedures, personnel, and In accordance with 10 CFR 50.55a(b)(2)(xv)(G), UT examinations performed using personnel, and equipment qualified in accordance with the ASME Code, Section Appendix VIII, Supplements 4 and 6, shall follow the following examination The clad to base metal interface, including a minimum of 15 percent T (measured from the clad to base metal interface), must be examined from four orthogonal directions using procedures and personnel qualified in accordance with Supplement 4 to Appendix VIII. If the clad-to-base-metal-interface procedure demonstrates detectability of flaws with a tilt angle relative to the weld centerline of at least 45 degrees, the remainder of the examination volume is considered fully examined if coverage is obtained in one parallel and one perpendicular direction. This must be accomplished using a procedure and personnel qualified for single-side examination in accordance with Supplement 6. Subsequent examinations of this volume may be performed using examination techniques qualified for a tilt angle of at least 10 degrees. The examination volume not addressed by paragraph (b)(2)(xv)(G)(1) of this section is considered fully examined if coverage is obtained in one parallel and one perpendicular direction, using a procedure and personnel qualified for single sided examination when the conditions in paragraph (b)(2)(xv)(G)(2) are met. UT examination procedures, personnel, and equipment qualified in accordance with the ASME Code,Section XI, Appendix VIII, following the examination coverage stated above, demonstrate a high probability of detecting flaws and increase the reliability of examinations of weld configurations within the scope of the PDI program. Therefore, the NRC staff concludes that proposed alternative provides an acceptable level of quality and safety. CONCLUSION The NRC staff has reviewed the licensee's proposed alternative to apply the ASME Code,Section XI, Appendix VIII performance demonstration requirements for UT examinations of the RPV shell-to-flange welds at STP, Units 1 and 2, and determined that the proposed alternative provides an acceptable level of quality and safety. The NRC staff concludes that procedures, personnel, and equipment qualified in accordance with the ASME Code,Section XI, Appendix VIII demonstrate a high probability of detecting flaws and increase the reliability of examinations of weld configurations within the scope of the PDI program. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes the use of the proposed alternative for the third 10-year lSI interval for STP, which ends on September 25, 2020, for Unit 1 and October 19,2020, for Unit 2.

-5 All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in the subject requests for relief remain applicable, including third-party review by the authorized Nuclear Inservice Inspector. Principal Contributor: Chris Sydnor, NRRIDCI/CVIB Date: October 14, 2011 E. Halpin -2 If you have any questions, please contact the project manager, Balwant K. Singal. at 301-415-3016 or via e-mail at Balwant.Singal@nrc.gov. Sincerely, IRAI Michael 1. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosure:

As stated cc w/encl: Distribution via Listserv DISTRIBUTION: PUBLIC LPLIV Reading RidsAcrsAcnw lVlailCTR Resource RidsNrrDciCvib Resource RidsNrrDorlDpr Resource RidsNrrDorlLpl4 Resource RidsNrrPMSouth Texas Resource RidsNrrLAJBurkhardt Resource RidsOgcRp Resource RidsRgn4MailCenter Resource JMcHale, EDO RIV CSydnor, NRR/DCI/CVIB ADAMS Accession No. ML 112650071 *Memo dated 9/19/11 OFFICE NRR/LPL4/PM NRR/LPL4/LA NRRIDCI/CVIB/BC (A) NRR/LPL4/BC NAME BSingal ,IBurkhardt MMitchell (SSheng for)* MMarkley DATE 10/11/11 10/5/11 9/19/11 10/14/11 OFFICIAL RECORD COpy