ML102500143

Relief Request No. 45 from Certain ASME Code Class 1 Weld and Component Volumetric Exams of Reactor Vessel Outlet Nozzles for Second 10-Year Inservice Inspection Interval

ML102500143
Person / Time
Site:	Palo Verde
Issue date:	09/21/2010
From:	Markley M T Plant Licensing Branch IV
To:	Edington R K Arizona Public Service Co
Hall, J R, NRR/DORL/LPL4,301-415-4032
References
TAC ME2311
Download: ML102500143 (8)

Text

UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555-0001 September 21, 2010 Mr. Randall K.

Executive Vice President Chief Nuclear Officer Mail Station 7602 Arizona Public Service Company P. O. Box 52034 Phoenix, AZ 85072-2034 PALO VERDE NUCLEAR GENERATING STATION, UNIT 2 -RELIEF REQUEST NO. 45 RE: SECOND 10-YEAR INSERVICE INSPECTION PROGRAM INTERVAL (TAC NO. ME2311)

Dear Mr. Edington:

By letter dated September 10, 2009, as supplemented by letter dated May 27,2010, Arizona Public Service Company (APS, the licensee) submitted Relief Request No. 45 (RR-45), requesting relief from certain American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) requirements at the Palo Verde Nuclear Generating Station (Palo Verde), Unit 2, for the second 1 O-year inservice inspection (lSI) program interval.

RR-45 requests relief from certain examination requirements of ASME Code,Section XI that the licensee considers to be impractical.

In an electronic mail dated March 26, 2010, the U.S. Nuclear Regulatory Commission (NRC) requested additional information concerning the APS submittal.

APS submitted its response by letter dated May 27,2010. The NRC staff has reviewed the licensee's submittal and has determined that granting RR-45, Part A, pursuant to paragraph 50.55a(g)(6)(i) of Title 10 of the Code of Federal Regulations (10 CFR) is authorized by law and will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

Relief is granted for the second 10-year lSI program interval at Palo Verde, Unit 2, based on the determination that the examination coverage requirements are impractical for the subject components listed in RR-45, Part A, and that the examinations performed to the extent practical provide reasonable assurance of structural integrity of the subject components.

In Part B of RR-45, APS requested relief for components associated with the chemical and volume control system (CVCS) charging pumps. APS stated that relief is being requested from the ASME Code,Section XI, requirement for visual test level II (VT-2) examinations of 100 percent of the nitrogen supply lines and valves for the CVCS charging pumps due to access limitations.

However, the NRC staff has determined that these nitrogen supply lines are not ASME Code components.

Therefore, the nitrogen supply lines and valves are not covered by 10 CFR 50.55a and ASME Code,Section XI, requirements, and the staff is not authorized to grant relief for performing a limited scope VT-2 examination of these components under 10 CFR 50.55a(g)(6)(i).

R. Edington -2 A copy of the related Safety Evaluation is enclosed.

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

If you have any questions, please contact Mr. Randy Hall at (301) 415-4032 or via e-mail at randy.hall@nrc.gov.

Sincerely, 'f-()/ ..........

-""'-'\ Michael T. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. STN Safety cc w/encl: Distribution via UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ON THE SECOND 10-YEAR INSERVICE INSPECTIOI\IINTERVAL RELIEF REQUEST NO. 45 ARIZONA PUBLIC SERVICE COMPANY, ET AL. PALO VERDE NUCLEAR GENERATING STATION, UNIT 2 DOCKET NO. STN 50-529

1.0 INTRODUCTION

By letter dated September 10, 2009 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML09261 0069), Arizona Public Service Company (the licensee) submitted Relief Request No. 45 (RR-45) for the Palo Verde Nuclear Generating Station (Palo Verde), Unit 2. In RR-45, the licensee requested relief from the examination requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, for several ASME Code Class 1 and 2 components at Palo Verde, Unit 2. The U.S. Nuclear Regulatory Commission (NRC) staff issued a request for additional information (RAI) by electronic mail (e-mail) dated March 26,2010 (ADAMS Accession No. ML 100850485), and the licensee responded to the RAI by letter dated May 27,2010 (ADAMS Accession No. ML 101590517).

The staff reviewed and evaluated Parts A and B of the licensee's request pursuant to the provisions of Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(6)(i), on the basis that the inservice inspection (lSI) Code requirements were impractical for the subject components.

2.0 REGULATORY EVALUATION

Inservice inspection 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 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).

The regulation in 10 CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if the licensee 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 50.55a(g)(4), ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the service 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 interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code, which was 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. The Code of record for the Palo Verde, Unit 2, second 10-year interval lSI program, which ended on March 17, 2007, is the 1992 Edition of the ASME Code,Section XI, through the 1992 Addenda. 3.0 TECHNICAL EVALUATION The information provided by the licensee in support of the request for relief from ASME Code requirements has been evaluated by the NRC staff and the bases for disposition are documented below. 3.1 Component Identification RR-45 addresses the following ASME Code,Section XI, Examination Categories and Item Numbers covering examinations of certain ASME Code Class 1 and 2 components (the subject components) for the second 10-year interval lSI program at Palo Verde, Unit 2. The following examination categories and item numbers are from Table IWB-2500-1 (Class 1 components) and IWC-2500-1 (Class 2 components) of the 1992 Edition and 1992 Addenda of the ASME Code,Section XI. ASME Code Class Examination Category Item Number(s)

Component Description 1 B-D B3.90 Reactor Vessel (RV), Nozzle-to-Vessel Welds 2 C-H C7.30 and C7.70 Piping, Pressure retaining components, and Valves, Pressure retaining components 3.2 NRC Staff Evaluation Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee submitted RR-45, requesting relief from the examination requirements of the ASME Code,Section XI, for the subject Class 1 and 2 components at Palo Verde, Unit 2. The 1992 Edition and 1992 Addenda of the ASME Code,Section XI, Articles IWB-2500 and IWC-2500 require that components be examined and tested as specified in Tables IWB-2500-1 and IWC-2500-1 of the ASME Code,Section XI. Tables IWB-2500-1 and IWC-2500-1 define the examination requirements for Class 1 and 2 components, respectively.

These tables specify, among other things, the examination techniques (volumetric, surface, and/or visual) and the examination boundary.

For each of the subject components, the examination boundary is provided in the figure specified for that

-3 particular ASME Code,Section XI, item number in Tables IWB-2500-1 and IWC-2500-1.

For vOlumetric and surface exams, the required examination boundary includes essentially 100 percent of the volume or area specified in the applicable figure listed in Tables IWB-2500-1 and IWC-2500-1.

Part A: Examination Category B-D. Item Number B3.90 -Reactor Vessel Nozzle-to-Vessel Welds In Part A of RR-45, the licensee requested relief from the ASME Code,Section XI requirements for examinations of RV Nozzle-to-Vessel Welds 1-15 and 1-18 at Palo Verde, Unit 2 (Examination Category B-D, Item Number B3.90). The licensee stated that the ASME Code,Section XI, as modified by ASME Code Case N-460, "Alternative Examination Coverage For Class 1 and Class 2 Welds,Section XI, Division 1," requires a volumetric examination of these welds, with a minimum coverage of 90 percent of the volume specified in Figure IWB-2500-7, as modified by ASME Code Case N-613-1, "Ultrasonic Examination of Full Penetration Nozzles in Vessels, Examination Category B-D, Item l\Ios. B3.10 and B3.90, Reactor Nozzle-To-Vessel Welds, Figs. IWB-2500-7(a), (b), and (c),Section XI, Division 1," for these welds. The NRC staff verified that the licensee's implementation of Code Cases N-460 and N-613-1 is consistent with Regulatory Guide (RG) 1.147, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1," October 2007. The licensee stated that the design of the RVoutlet nozzle protrusion provided a geometric limitation to the ultrasonic scanning area. The examination robot and ultrasonic transducer sled are physically limited from achieving full ultrasonic scans by this protrusion.

The licensee provided figures illustrating where the limitations were documented in the vicinity of the nozzle-to-vessel protrusion, and a typical transducer sled scanning from the RV inside diameter (10). These figures illustrate the limitation caused by the nozzle protrusion.

The licensee stated that ultrasonic scanning was performed on RV Nozzle-to-Vessel Welds 1-15 and 1-18 to the fullest extent practical, resulting in a volumetric examination coverage of 94 percent for ultrasonic scans in the direction perpendicular to the weld centerline and 56.94 percent for ultrasonic scans in the direction parallel to the weld centerline.

The overall combined examination volume coverage was 75.47 percent. The licensee stated that full compliance with the ASME Code,Section XI examination requirements for these welds would require redesign and modification of the RV nozzle attachments in order achieve greater than 90 percent examination coverage.

The NRC staff reviewed the information provided by the licensee concerning the impracticality of achieving full volumetric coverage of RV Nozzle-to-Vessel Welds 1-15 and 1-18, as discussed above, and agreed with the licensee's determination that the RV outlet nozzle protrusion did prevent the performance of ultrasonic scans with greater than 90 percent volumetric coverage.

Therefore, the staff agreed with the licensee's determination that achieving the VOlumetric examination coverage required by the ASME Code,Section XI is impractical for RV Nozzle-to-Vessel Welds 1-15 and 1-18. However, the staff noted that the licensee did not provide information concerning the results of the limited volumetric examinations for these welds. Therefore, in an RAI dated March 26, 2010, the staff requested that the licensee discuss the results of the limited volumetric examinations of RV Vessel Welds 1-15 and 1-18. In its RAI response dated May 27,2010, the licensee stated that the volumetric examinations of RV Nozzle-to-Vessel Welds 1-15 and 1-18 resulted in no unacceptable indications.

The staff concluded that the licensee's RAI response was acceptable

-because the limited volumetric examinations of RV Nozzle-to-Vessel Welds 1-15 and 1-18 resulted in no unacceptable indications.

Based on the above considerations, the staff determined that the ASME Code,Section XI requirement to perform volumetric examinations of RV Nozzle-to-Vessel Welds 1-15 and 1-18, with essentially 100 percent coverage, is impractical for Palo Verde, Unit 2. The licensee's limited volumetric examinations provide reasonable assurance of continued structural integrity for RV Nozzle-to-Vessel Welds 1-15 and 1-18 at Palo Verde, Unit 2. Part B: Examination Category C-H, Item Number C7.30 -Piping, Pressure Retaining Components and Examination Category C-H, Item Number C7.70 -Valves, Pressure Retaining Components In Part B of RR-45, the licensee requested relief from the ASME Code,Section XI, requirements for visual test level II (VT-2) examinations of several Examination Category C-H, Item No. C7.30 and Item No. C7.70 components at Palo Verde, Unit 2. The licensee requested relief for components associated with the chemical and volume control system (CVCS) charging pumps. The CVCS charging pumps each have a suction stabilizer and pulsation dampener for system stability purposes.

These components have a bladder and nitrogen system to moderate the fluid shock in the CVCS to maintain consistent operating characteristics.

The licensee stated that relief is being requested from the ASME Code,Section XI, requirement for a VT-2 visual examination of 100 percent of the nitrogen supply lines and valves for the CVCS charging pumps due to access limitations.

However, the NRC staff determined that these nitrogen supply lines are not ASME Code components.

Therefore, the nitrogen supply lines and valves are not covered by 10 CFR 50.55a and ASME Code,Section XI, requirements, and the staff is not authorized to grant relief for performing a limited scope VT-2 examination of these components under 10 CFR 50.55a(g)(6)(i).

The staff made a similar determination in Relief Request No. 46, issued for Palo Verde, Unit 1, on July 27, 2010 (ADAMS Accession No. ML 102000612).

4.0 CONCLUSION

Based on the above evaluation of RR-45, Part A, the NRC staff concludes that the applicable ASME Code,Section XI examination requirements are impractical for the subject Class 1 components at Palo Verde, Unit 2. Furthermore, the staff concludes that the licensee's alternative examinations provide reasonable assurance of structural integrity for the subject Class 1 components.

The staff further concludes that granting relief pursuant to 10 CFR 50.55a(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 giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

Therefore, RR-45, Part A, is authorized pursuant to 10 CFR 50.55a(g)(6)(i) for the second 10-year interval lSI program at Palo Verde, Unit 2. The staff cannot grant relief as requested in RR-45, Part B for the CVCS charging pump nitrogen supply lines, pursuant to 10 CFR 50.55a(g)(6)(i), because these components are not subject to 10 CFR 50.55a and ASME Code,Section XI, requirements.

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

Principal Contributor:

C. Sydnor Date: September 21, 2010 R. Edington -2 A copy of the related Safety Evaluation is enclosed.

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

If you have any questions, please contact Mr. Randy Hall at (301) 415-4032 or via e-mail at randy.hall@nrc.gov.

Sincerely, IRN Michael 1. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. STN Safety cc w/encl: Distribution via Listserv DISTRIBUTION:

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(*) MMarkley DATE 9/20/10 9/20/10 7/26/10 9/21/10 OFFICIAL AGENCY