ML082630051

Inservice Inspection Program Relief Request PD1-4

ML082630051
Person / Time
Site:	Browns Ferry
Issue date:	10/03/2008
From:	Boyce T Plant Licensing Branch II
To:	Campbell W Tennessee Valley Authority
Boyce T, NRR/ADRO/DORL/301-415-0184
References
TAC MD8798
Download: ML082630051 (9)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 October 3, 2008 Mr. William R. Campbell, Jr.

Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801

SUBJECT:

BROWNS FERRY NUCLEAR PLANT UNIT 1 - INSERVICE INSPECTION PROGRAM RELIEF REQUEST PDI-4 (TAC NO. MD8798)

Dear Mr. Campbell:

Bya letter dated May 27,2008, the Tennessee Valley Authority (TVA, the licensee) submitted Relief Request (RR) 1-PDI-4 requesting relief from the requirements specified in Appendix I to the American Society of Mechanical Engineers Code (ASME),Section XI for the Reactor Pressure Vessel (RPV) circumferential shell-to-flange and RPV closure head-to-flange welds under Title 10, Code of Federal Regulations (10 CFR), Section 50.55a(a)(3)(i) for the Browns Ferry Nuclear Plant, Unit 1. The request proposed that in lieu of the requirements of the ASME Code,Section XI, Subarticle IWA-2232 and its referenced Section V, Article 4 requirements, the procedures, personnel, and equipment qualified to meet the requirements of ASME Section XI, Appendix VIII, Supplements 4 and 6 of the 2001 Edition, as administered by the Electric Power Research Institute's Performance Demonstration Initiative (PDI) processes be used to conduct the required examinations for the RPV circumferential shell-to-flange flange and RPV closure head-to-flange welds.

The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of the information provided in TVA's May 27, 2008, letter. The NRC staff concluded that the proposed alternative to the requirements of Section XI, paragraph IWA-2232 of the ASME Code described in the licensee's letter provides an acceptable level of quality and safety. Therefore, RR-1-PDI-4 is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for Browns Ferry Nuclear Plant, Unit 1. All other requirements of the ASME Code,Section XI for which relief was not specifically requested and approved in this relief request remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.

This relief is authorized for the remainder of the second 1O-year inservice inspection interval at Browns Ferry Unit 1, which began June 2, 2008, and is scheduled to end June 1, 2018.

Sincerely,

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Th~~~' ~~i~O~C~, 'dhi~f Plant Licensing ~ranch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-259

Enclosure:

Safety Evaluation cc w/encl: See next page

• ML082630051 OFFICE LPL2-2/PM LPL2-2/LA CPNB/BC OGC LPL2-2/SC NAME EBrown BClayton TChan by memo DRoth "NLO" TBoyce DATE 10/02/08 10/01108 8/27/08 9/24/08 10/03/08 Letter to William R. Campbell, Jr. from Eva A. Brown dated: October 3, 2008

SUBJECT:

BROWNS FERRY NUCLEAR PLANT UNIT 1 - INSERVICE INSPECTION PROGRAM RELIEF REOUEST PDI-4 (TAC NO. MD8798)

Distribution:

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Page 1 of 2 Tennessee Valley Authority BROWNS FERRY NUCLEAR PLANT cc:

IVIr. Ashok S. Bhatnagar Mr. R. G. (Rusty) West Senior Vice President Site Vice President Nuclear Generation Development Browns Ferry Nuclear Plant and Construction Tennessee Valley Authority Tennessee Valley Authority P.O. Box 2000 6A Lookout Place Decatur, AL 35609 1101 Market Street Chattanooga, TN 37402-2801 Ms. Beth A. Wetzel, Manager Corporate Nuclear Licensing Vice President and Industry Affairs Nuclear Support Tennessee Valley Authority Tennessee Valley Authority 4K Lookout Place 3R Lookout Place 1101 Market Street 1101 Market Street Chattanooga, TN 37402-2801 Chattanooga, TN 37402-2801 Mr. James E. Emens, Jr.

Mr. Michael J. Lorek Supervisor, Nuclear Site Licensing Vice President Browns Ferry Nuclear Plant Nuclear Engineering & Projects Tennessee Valley Authority Tennessee Valley Authority P.O. Box 2000 3R Lookout Place Decatur, AL 35609 1101 Market Street Chattanooga, TN 37402-2801 James B. Baptist Browns Ferry Senior Project Engineer Mr. D:Tony Langley, Manager Division of Reactor Projects, Branch 6 Licensing and Industry Affairs U.S. Nuclear Regulatory Commission Browns Ferry Nuclear Plant 61 Forsyth Street, SW.

Tennessee Valley Authority Suite 24T85 P.O. Box 2000 Atlanta, GA 30303-8931 Decatur, AL 35609 Senior Resident Inspector General Counsel U.S. Nuclear Regulatory Commission Tennessee Valley Authority Browns Ferry Nuclear Plant 6A W est Tower 10833 Shaw Road 400 West Summit Hill Drive Athens, AL 35611-6970 Knoxville, TN 37902 State Health Officer Mr. John C. Fornicola, General Manager Alabama Dept. of Public Health Nuclear Assurance RSA Tower - Administration Tennessee Valley Authority Suite 1552 3R Lookout Place P.O. Box 303017 1101 Market Street Montgomery, AL 36130-3017 Chattanooga, TN 37402-2801

Page 2 of 2 Tennessee Valley Authority BROWNS FERRY NUCLEAR PLANT cc:

Chairman Limestone County Commission 310 West Washington Street Athens, AL 35611 Mr. Larry E. Nicholson, General Manager Performance Improvement Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. Michael A. Purcell Senior Licensing Manager Nuclear Power Group Tennessee Valley Authority 4K Lookout Place 1101 Market Street Chattanooga, TN 37402-2801

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION INSERVICE INSPECTION PROGRAM TENNESSEE VALLEY AUTHORITY BROWNS FERRY NUCLEAR PLANT, UNIT 1 DOCKET NO. 50-259

1.0 INTRODUCTION

By letter dated May 27,2008, the Tennessee Valley Authority (TVA, the licensee) submitted a relief request from certain qualification requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code at the Browns Ferry Nuclear Plant, Unit 1.

Specifically, the licensee proposed (Relief Request 1-PDI-4) examining the reactor pressure vessel (RPV) closure head-to-flange weld and circumferential RPV shell-to-flange weld with procedure and personnel qualified to ASME Code,Section XI, Appendix VIII, Supplements 4 and 6 requirements.

The request is for the remainder of the second 1O-year inservice inspection (lSI) interval that began June 2, 2008, and is scheduled to end June 1, 2018.

2.0 REGULATORY REQUIREMENTS The lSI of the ASME Code Class 1, 2, and 3 components is to be performed in accordance with Section XI of the ASME Code and applicable edition and addenda as required by Title 10 Code of Federal Regulations (10 CFR) Section 50.55a(g), except where specific relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i). In 10 CFR 50.55a(a)(3), it states, in part, that alternatives to the requirements of paragraph (g) may be used when authorized by the Nuclear Regulatory Commission (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.

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) will 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 regulations require that inservice examination of components and system pressure tests conducted during the first 1O-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 50.55a(b) 12 months prior to Enclosure

-2 the start of the 120-month interval, subject to the limitations and modifications listed therein. As stated in 10 CFR 50.55a(g)(4)(iv), inservice examination of components and system pressure tests may meet the requirements set forth in subsequent editions and addenda that are incorporated by reference in paragraph 10 CFR 50.55a(b), subject to the limitations and modification listed in 10 CFR 50.55a(b) and subject to Commission approval. Portions of editions or addenda may be used provided that all related requirements of the respective editions or addenda are met.

The code of record for the second 1O-year lSI interval at the Browns Ferry Nuclear Plant, Unit 1, is the 2001 Edition through 2003 Addenda of the ASME Code.

3.0 RELIEF REQUEST NO. 1-PDI-4 3.1 Component Function/Description ASME Code Class 1, RPV upper vessel shell-to-flange weld and RPV closure head-to-flange weld, Table IWB-2500-1, Category B-A, Item Numbers B1.30 and B1.40, TVA lSI program weld designations 1-C-5-FLG and RCH-1-2C.

3.2 Code Requirements for Which Relief is Requested ASME Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components,"

2001 Edition through 2003 Addenda, Subsection IWA-2232 "Ultrasonic examinations shall be conducted in accordance with Appendix I." Appendix I, paragraph 1-211 O(b) states that, Ultrasonic examinations of the RPV-to-flange weld, closure head-to-flange welds, and integral attachment welds shall be conducted in accordance with ASME Section V, Article 4, except that alternative examination beam angles may be used.

Regulatory Guide (RG) 1.150, Revision 1, Ultrasonic Testing of Reactor Vessel Welds During Preservice and Inservice Examinations, provides guidance for LIT examinations of RPV welds.

3.3 Licensee's Proposed Alternative The licensee proposes using the techniques (procedures), personnel, and equipment qualified to meet the requirements of the 2001 Edition of the ASME Code,Section XI, Appendix VIII, Supplements 4 and 6, in accordance with 10 CFR 50.55a(b)(2)(xxiv) and, as amended by Sections 10 CFR 50.55a(b)(2)(xv)(B) through 10 CFR 50.55a(b)(2)(xv)(G), and 10 CFR 50.55a(b)(2)(xvi)(A), as administered by the Electric Power Research Institute's (EPRI)

Performance Demonstration Initiative (PDI) program.

3.4 Licensee's Bases for Alternative Section V, Article 4 of the ASME Code, describes the required techniques to be used for the ultrasonic testing (UT) of welds in ferritic pressure vessels with wall thicknesses greater than 2-inches. UT performed in accordance with Section V, Article 4, uses recording thresholds of 50 percent distance-amplitude-correction (DAC) for the outer 80 percent of the required examination volume and 20 percent DAC from the clad/base metal interface to the inner 20 percent margin of the examination volume. Indications detected in the designated exam volume portions, with amplitudes below these thresholds, are not required to be recorded. Use of

-3 the Appendix VIII/POI processes would enhance the quality of the examination results reported because the detection sensitivity is more conservative and the procedure requires the examiner to evaluate all indications determined to be flaws, regardless of their associated amplitude. The recording thresholds in Section V, Article 4, and the guidelines of RG 1.150, Revision 1, are generic and somewhat arbitrary and do not take into consideration such factors as flaw orientation, which can influence the amplitude of LIT responses.

The EPRI Report NP-6273, Accuracy of Ultrasonic Flaw sizing Techniques for Reactor Pressure Vessels, dated March 1989, established that LIT flaw sizing techniques based on tip diffraction are the most accurate. The qualified prescriptive-based LIT procedures of ASME Section V, Article 4 have been applied in a controlled process with mockups of RPVs that contained real flaws and the results statistically analyzed according to the screening criteria in ASME Section XI, Appendix VIII. The results show that the procedures in Section V, Article 4 are less effective in detecting flaws than procedures qualified in accordance with Appendix VIII as administered by the POI program. Appendix VIII/POI qualification procedures use the tip diffraction techniques for flaw sizing. The proposed alternative Appendix VIII/POI LIT methodology uses analysis tools based upon echo dynamic motion and tip diffraction criteria, which has been validated, and is considered more accurate than the Section V, Article 4 processes.

3.5 Evaluation The 2001 Edition of the ASME Code,Section V, Article 4, as supplemented by Appendix I provides a prescriptive process for qualifying LIT procedures. In lieu of 1-21 OO(b) requirements, the licensee proposed using procedures, equipment, and personnel qualified in accordance with performance-based criteria as administered by the POI program for the examination of RPV welds.

The POI program implements the requirements of Section XI, Appendix VIII, Supplements 4 and 6 as modified by 10 CFR 50.55a(b)(2)(xv).

When prescriptive Section V, Article 4 LIT procedures are applied in a controlled setting containing real flaws in mockups and the sizing results are statistically analyzed according to the performance-based screening criteria in Section XI, Appendix VIII, the prescriptive-based sizing results were determined to be equal to or less effective than the sizing results from performance-based Section XI, Appendix VIII procedures. The improvement in sizing is attributed to the echo-dynamic motion and tip diffraction criteria used by p~rformance-based LIT as opposed to the less accurate amplitude drop criteria of prescriptive Section V, Article 4 requirements.

Recently, the ASME Code approved a change that permitted licensees to use Appendix VIII qualified procedures, personnel, and equipment for examinations of components to which Appendix VIII is not applicable provided the component materials, sizes, and shapes are with the scope of the qualified examination procedures. The ASME Code Appendix VIII LIT qualifications are more rigorous than ASME Section V, Article 4 qualifications. Appendix VIII qualifications are based on passing a blind test performed on representative mockups containing representative flaws, while an ASME Section V, Article 4 qualification process relies on non-blind detection of machined marks in a calibration block.

For detection of flaws,Section V, Article 4 and RG 1.150 require indications of 20 percent OAC displayed on a cathode ray tube (CRT) screen and greater to be evaluated. Performance-based LIT requires that the essential variable settings used during the performance demonstration be

-4 used for the examinations, which usually is DAC above the background noise displayed on the CRT. The performance-based UT is performed with higher sensitivity, which increases the chances of detecting a flaw when compared to prescriptive Section V, Article 4 requirements.

Procedures, equipment, and personnel qualified through the POI program have shown high probability of detection levels. Based on this, the NRC staff concludes that this will result in an acceptable level of quality and safety per 50.55a(3)(i) of inspections for weld configurations within the scope of the POI program.

4.0 CONCLUSION

Based on the increased reliability of inspections within the scope of the POI program, as discussed above, the staff concludes that the licensee's proposed alternative in RR-PDI-4 to use UT procedures, equipment, and personnel qualified to the 2001 Edition of the ASME Section XI, Appendix VIII, Supplements 4 and 6 as modified by 10 CFR 50.55a for the RPV shell-to-flange weld and RPV head-to-flange weld, is acceptable. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i),

the proposed alternative in RR-1-PDI-4 is authorized for the subject welds for the remainder of the second 1O-year lSI interval at Browns Ferry Nuclear Plant, Unit 1, that began June 2, 2008, and is scheduled to end June 1, 2018. This authorization is limited to those components described in Section 3.1 above.

All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third party review by the Authorized Nuclear lnservice Inspector.

Principal Contributor: Donald Naujock Date: October 3, 2008