ML100620869

Authorization of Relief Request RR-ENG-2-53, Alternative to Inservice Inspection Requirements for Ultrasonic Exam of Reactor Pressure Vessel Shell-to-Flange Weld

ML100620869
Person / Time
Site:	South Texas
Issue date:	03/24/2010
From:	Markley M Plant Licensing Branch IV
To:	Halpin E South Texas
Thadani, M C, NRR/DORL/LPL4, 415-1476
References
TAC ME2329, TAC ME2330
Download: ML100620869 (8)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 March 24, 2010 Mr. Edward D. Halpin President and Chief Executive Officer STP Nuclear Operating Company South Texas Project P. O. Box 289 Wadsworth, TX 77483

SUBJECT:

SOUTH TEXAS PROJECT, UNITS 1 AND 2 - AUTHORIZATION OF RELIEF REQUEST NO. RR-ENG-2-53, REGARDING USE OF ALTERNATIVE TO ULTRASONIC EXAMINATION OF REACTOR PRESSURE VESSEL SHELL-TO FLANGE WELDS (TAC NOS. ME2329 AND ME2330)

Dear Mr. Halpin:

By letter dated September 23, 2009 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML092720458), as supplemented by an electronic mail dated October 15, 2009 (ADAMS Accession No. ML092880990), and letter dated November 11, 2009 (ADAMS Accession No. ML093210175), STP Nuclear Operating Company (the licensee) requested relief from the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) for inservice inspection (lSI) under the provisions of Title 10 of the Code of Federal Regulations (10 CFR) paragraph 50.55a(a)(3)(i) at South Texas Project (STP), Units 1 and 2. ASME Code Section XI, 1995 Edition through 1996 Addenda, Appendix I, Article 1-2110(b), requires ultrasonic examination of the reactor pressure vessel (RPV) shell-to-flange welds in accordance with ASME Code,Section V, Article 4. The proposed alternative would allow the RPV shell-to-flange weld examination to be performed with procedures, equipment, and personnel qualified to the Performance Demonstration Initiative requirements of ASME Code,Section XI, 1995 Edition through 1996 Addenda, Appendix VIII, Supplements 4 and 6, as modified by 10 CFR 50.55a.

The Nuclear Regulatory Commission (NRC) staff reviewed the licensee's request for approval of the alternative. On the basis of that review, the NRC staff has determined that relief request RR-ENG-2-53 will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes the use of the Relief Request RR-ENG-2-53 for the examination of the RPV shell-to-flange welds at STP, Units 1 and 2, for the remainder of the second 1O-year lSI interval. The second 10-year lSI interval ends on September 25, 2010, for Unit 1, and on October 19, 2010, for Unit 2.

On October 16, 2009, the NRC staff verbally authorized the licensee to use the Relief Request RR-ENG-2-53. The summary of the verbal authorization is documented in a memorandum dated October 20,2009 (ADAMS Accession No. ML092890456).

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

E. Halpin -2 The NRC staff's safety evaluation is enclosed.

Sincerely, ttl] /)r" l I!)I l"')n...V... / ( .

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. . ~ rkley T. Markley, Chief Plant Licensing Branch IV

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i II Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosure:

Safety Evaluation cc w/encl: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO USE OF ALTERNATIVE TO ULTRASONIC EXAMINATION OF REACTOR PRESSURE VESSEL SHELL-TO-FLANGE WELD RELIEF REQUEST NO. RR-ENG-2-53 STP NUCLEAR OPERATING COMPANY, ET AL.

SOUTH TEXAS PROJECT, UNITS 1 AND 2 DOCKET NOS. 50-498 AND 50-499

1.0 INTRODUCTION

By letter dated September 23, 2009 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML092720458), as supplemented by an electronic mail dated October 15, 2009 (ADAMS Accession No. ML092880990), and letter dated November 11, 2009 (ADAMS Accession No. ML093210175), STP Nuclear Operating Company (the licensee) requested relief from the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) inservice inspection (lSI) requirements under the provisions of Title 10 of the Code of Federal Regulations (10 CFR) paragraph 50.55a(a)(3)(i) at South Texas Project (STP), Units 1 and 2. ASME Code,Section XI, 1995 Edition through 1996 Addenda, Appendix I, Article 1-211 O(b), requires ultrasonic examination of the reactor pressure vessel (RPV) shell-to-f1ange welds in accordance with ASME Code,Section V, Article 4. The proposed alternative allows the RPV shell-to-flange welds examination to be performed with procedures, equipment, and personnel qualified to the Performance Demonstration Initiative (POI) requirements of ASME Code,Section XI, 1995 Edition through 1996 Addenda, Appendix VIII, Supplements 4 and 6, as modified by 10 CFR 50.55a.

Bye-mail dated October 15, 2009, the licensee responded to the Nuclear Regulatory Commission (NRC) staff's October 15, 2009, request for additional information (RAI) (ADAMS Accession No. ML092880392) regarding the subject relief request. On October 16, 2009, the NRC staff verbally authorized the licensee the use of relief request RR-ENG-2-53. As part of the verbal authorization, the licensee agreed to revise the relief request to include the clarifying information provided in its October 15, 2009, e-mail response to the NRC staff RAI.

By letter dated November 11, 2009, the licensee submitted the revised relief request, incorporating responses to the NRC staff's RAI. The changes in the revised relief request are consistent with the application as verbally approved by the NRC staff and do not change the technical content of the initial application dated September 23, 2009.

Enclosure

-2

2.0 REGULATORY EVALUATION

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 (lSI) 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 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 the start of the 120-month interval, subject to the limitations and modifications listed therein.

Pursuant to 10 CFR 50.55a(a)(3), alternatives to requirements may be authorized by the NRC if the licensee demonstrates that: (i) the proposed alternative provides 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.

The Code of record for the second 10-year lSI interval for STP, Units 1 and 2 is the ASME Code,Section XI, the 1989 Edition, no Addenda.

3.0 TECHNICAL EVALUATION

3.1 Relief Request RR-ENG-2-53 3.1.1 Affected Components (as stated by the licensee)

Reactor Pressure Vessel (RPV) shell-to-flange welds RPV1-101-121 (ASME Code Section XI, Table IWB-2500-1, Examination Category B-A, Item B1.30) 3.1.2 Applicable ASME Code The current Code of record for STP, Units 1 and 2, is the ASME Code,Section XI, 1989 Edition, no Addenda. The current inspection interval for STP is the second inspection interval.

However, by a safety evaluation dated on September 28, 2001 (ADAMS Accession No. ML012710500), the NRC approved the licensee's Relief Request RR-ENG-2-22 to apply selected sections (Appendix I, Appendix VIII, and IWA-2300) of the ASME Code,Section XI, 1995 Edition through the 1996 Addenda, as alternative criteria for performing ultrasonic examinations and qualification of examination personnel to POI requirements.

3.1.3 Code Requirement for Which Alternative is Proposed (as stated by the licensee)

The ASME Code,Section XI, 1989 Edition, IWA-2232 requires that ultrasonic (UT) examinations be conducted in accordance with Appendix I. By [the] NRC

[staff's] safety evaluation dated September 28, 2001 (ML012710500), the STP Nuclear Operating Company (STPNOC) is approved to apply the ASME [Code],

Section XI, 1995 Edition through 1996 Addenda as alternative criteria for

-3 performing Appendix VIII-qualified ultrasonic examinations and qualification of examination personnel. [The] 1995 Edition [through the] 1996 Addenda, Appendix I, Article 1-2110(b) requires that UT examination of the RPV shell-to-flange weld be performed in accordance with the ASME Code,Section V, Article 4. STPNOC proposes an alternative to [the ASME Code, Section Xl,]

Appendix I for [the] RPV shell-to-flange weld examination.

3.1.4 Basis for Relief from Code Requirements (as stated by the licensee)

[The] ASME Code,Section V, Article 4, applies a prescriptive-based process for qualifying UT procedures and performing examinations. The prescriptive-based process has been replaced by performance-based methods implemented by [the]

ASME [Code,] Section XI, 1995 Edition [through] 1996 Addenda, Appendix VIII,

[including] Supplements 4 and 6. 10 CFR 50.55a requires the use of performance-based methods for examination of RPV shell welds.

Although not the [ASME] Code edition currently applicable to the South Texas Project, ASME [Code] Section XI, 2004 Edition [through] 2005 Addenda, Appendix I, Article 1-2600(a) states that for components to which Appendix VIII is not applicable [Article 1-211 O(b)], examination procedures, personnel, and equipment qualified in accordance with Appendix VIII may be applied. Industry experience has shown that the Appendix VIII PDI approach has demonstrated that for detection and characterization of flaws in the RPV, the UT examination techniques equal or surpass the requirements of the ASME Code,Section V, Article 4 UT examination requirements.

3.1.5 Proposed Alternative (as stated by the licensee)

The proposed alternative, as verbally approved for application to the RPV shell to-flange weld is in accordance with the performance-based methods of ASME

[Code,] Section XI 1995 Edition [through] 1996 Addenda, Appendix VIII, Supplements 4 and 6, as modified by 10 CFR 50.55a.

3.1.6 Implementation Schedule (as stated by the licensee)

The alternative RPV shell-to-flange weld examination requirements as described above are to be applied in both the Unit 1 and Unit 2 current 1O-year inservice inspection intervals. The intervals end September 25, 2010, for Unit 1, and October 19, 2010, for Unit 2. The Unit 1 alternative examination has been completed, and the Unit 2 alternative examination will be performed during the refueling outage scheduled for March 2010.

3.2 Staff Evaluation The 1989 Edition of the ASME Code,Section V, Article 4, as supplemented by Appendix I, provides a prescriptive process for qualifying UT procedures. In lieu of the requirements of the ASME Code,Section XI, Appendix I, Article 1-2100(b), the licensee proposed to use procedures, equipment, and personnel qualified in accordance with performance-based criteria as

-4 administered by the POI program for the examination of RPV shell-to-flange weld, RPV1-101-121. The POI program implements the requirements of the ASME Code, 1995 Edition through 1996 Addenda,Section XI, Appendix VIII, Supplements 4 and 6, as modified by 10 CFR 50.55a(b)(2)(xv).

When prescriptive UT procedures of the ASME Code,Section V, Article 4, were applied in a controlled setting containing real flaws in mockups and the sizing results were statistically analyzed according to the performance-based screening criteria in the ASME Code,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, ASME Code,Section XI, Appendix VIII procedures as documented in Electric Power Research Institute Report NP-6273, "Accuracy of Ultrasonic Flaw Sizing Techniques for Reactor Pressure Vessels," dated March 1989. The better sizing resulting from the use of the ASME Code,Section XI, Appendix VIII, is attributed to the echo-dynamic motion and tip diffraction criteria used by performance-based UT techniques as opposed to the less accurate amplitude drop criteria of prescriptive-based requirements of the ASME Code,Section V, Article 4.

Recently, the ASME Code approved a change that permitted licensees to use the ASME Code,Section XI, Appendix VIII-qualified procedures, equipment, and personnel for examinations of components for which Appendix VIII was not applicable, provided that the component's material, size, and shape were within the scope of the qualified examination procedure. The NRC staff participated in the ASME Code committee approval process and supported this action because the NRC staff noted that the UT qualifications per the ASME Code,Section XI, Appendix VIII are more rigorous than the UT qualifications per the ASME Code,Section V, Article 4. The ASME Code,Section XI, Appendix VIII qualifications are based on passing a blind test performed on representative mockups containing representative flaws, while the Section V, Article 4 qualification process relies on non-blind detection of machined marks in a calibration block.

For flaw detection and evaluation, the ASME Code,Section V, Article 4 requires that an indication display a 20 percent or greater Oistance Amplitude Correction Curve (OAC) on a cathode ray tube (CRT) screen. For performance-based UT, the essential variable settings used during the performance demonstration are required for the examination which usually relies on a CRT image display of twice the background noise. The performance-based UT is conducted with higher sensitivity which increases the chances of detecting a flaw when compared to the OAC requirements of the prescriptive-based requirements of the ASME Code,Section V, Article 4. Procedures, equipment, and personnel qualified to meet the ASME Code,Section XI, Appendix VIII requirements have a high probability of flaw detection. Based on the above discussion, the NRC staff concludes that the use of Appendix VIII results in an increased reliability for the inspection of weld configurations within the scope of the POI qualified procedures, equipment and personnel.

In Section 4.0 of relief request RR-ENG-2-53, the licensee discussed the 2004 Edition through 2005 Addenda of the ASME Code,Section XI. The NRC staff noted that it has not yet incorporated by reference the 2005 Addenda of the ASME Code in 10 CFR 50.55a. In its response to the staff's RAI dated October 15, 2009, the licensee clarified that the discussion of the 2004 Edition through 2005 Addenda in the relief request is for reference purposes only and that it does not intend to use the 2004 Edition or the 2005 Addenda of the ASME Code,

-5 Section XI. Subsequently, the licensee revised the original relief request dated September 23, 2009, to clarify its intent of discussing the 2004 Edition through 2005 Addenda of the ASME Code,Section XI. The NRC staff concludes that the revised Section 4 as described in the relief request dated November 11, 2009, is acceptable.

4.0 CONCLUSION

Based on the increased reliability of inspections conducted within the scope of the Appendix VIII POI program, the NRC staff concludes that the licensee's proposed alternative to use UT procedures, equipment, and personnel qualified to the 1995 Edition through 1996 Addenda of the ASME Code,Section XI, Appendix VIII, Supplements 4 and 6, as modified by 10 CFR 50.55a to examine RPV shell-to-flange weld RPV1-101-121, provides an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the NRC staff authorizes the use of Relief Request RR-ENG-2-53 for the examination of weld RPV1-1 01-121 for STP, Units 1 and 2, for the remainder of the second 10-year lSI interval. The second 10 year lSI interval ends on September 25, 2010, for Unit 1, and on October 19, 2010, for Unit 2.

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

Principal Contributor: J. Tsao Date: March 24, 2010

E. Halpin -2 The NRC Staff's safety evaluation is enclosed.

Sincerely, IRA by James R. Hall fori Markley 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:

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