ML18296A717

Relief Request Regarding Examination Coverage for Certain Pressurizer and Steam Generator Welds (VEGP-ISI-RR-03)

ML18296A717
Person / Time
Site:	Vogtle
Issue date:	10/31/2018
From:	Markley M Plant Licensing Branch II
To:	Gayheart C Southern Nuclear Operating Co
Orenak, M D, NRR/DORL/LPLII-1, 415-3229
References
EPID L-2017-LLR-0075, VEGP-ISI-RR-03
Download: ML18296A717 (8)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 31, 2018 Ms. Cheryl A. Gayheart Regulatory, Affairs Director Southern Nuclear Operating Co., Inc.

3535 Colonnade Parkway Birmingham, AL 35243

SUBJECT:

VOGTLE ELECTRIC GENERATING PLANT, UNITS 1 AND 2-RELIEF REQUEST REGARDING EXAMINATION COVERAGE FOR CERTAIN PRESSURIZER AND STEAM GENERATOR WELDS (VEGP-ISI-RR-03)

(EPID L-2018-LLR-0075)

Dear Ms. Gayheart:

By letter dated May 24, 2018, as supplemented by letter dated September 26, 2018, Southern Nuclear Operating Company (SNC or the licensee) submitted three requests for relief from certain requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code, Section XI. One of those relief requests, VEGP-ISI-RR-03, pertains to examination coverages of some pressurizer and steam generator welds achieved during the third inservice inspection (ISi) interval at Vogtle Electric Generating Plant (Vogtle),

Units 1 and 2.

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),

the licensee requested relief from the required examination coverage and to use alternative requirements for inspection of Category B-B, Item Nos. B2.11 (Pressurizer Shell-to-Head Circumferential Weld), 82.40 (Steam Generator Tubesheet-to-Channel Head Weld), and Category B-D, Item No. B3.110 (Pressurizer Nozzle-to-Vessel Weld) on the basis that the ASME Code requirement is impractical.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the relief request and concludes, as set forth in the enclosed safety evaluation, that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii). Therefore, in accordance with 10 CFR 50.55a(g)(6)(i), the NRC staff grants relief request VEGP-ISI-RR-03, for Vogtle, Units 1 and 2, for the third 10-year ISi interval, which ended on May 30, 2017.

All other ASME BPV Code, Section XI, requirements for which relief was not specifically requested and authorized herein by the staff remain applicable, including the third-party review by the Authorized Nuclear lnservice Inspector.

C. A. Gayheart If you have any questions, please contact the Vogtle project manager, Michael Orenak, at 301-415-3229 or by e-mail at Michael.Orenak@nrc.gov.

Sincerely, Michael T. Markley, Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-424 and 50-425

Enclosure:

Safety Evaluation cc: Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST VEGP-ISI-RR-03 REGARDING EXAMINATION COVERAGE FOR CERTAIN PRESSURIZER AND STEAM GENERATOR WELDS SOUTHERN NUCLEAR OPERATING COMPANY. INC.

VOGTLE ELECTRIC GENERATING PLANT. UNITS 1 AND 2 DOCKET NUMBERS 50-424 AND 50-425

1.0 INTRODUCTION

By letter dated May 24, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML181448012), as supplemented by letter dated September 26, 2018 (ADAMS Accession No. ML18269A094), Southern Nuclear Operating Company (SNC or the licensee) submitted three requests for relief from certain requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code, Section XI. One of those relief requests, VEGP-ISI-RR-03, pertains to examination coverages of some pressurizer and steam generator welds achieved during the third inservice inspection (ISi) interval at Vogtle Electric Generating Plant, Units 1 and 2 (Vogtle ).

Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(g)(5)(iii),

the licensee requested relief from the required examination coverage and to use alternative requirements for inspection of Category B-B, Item Nos. 82.11 (Pressurizer Shell-to-Head Circumferential Weld), 82.40 (Steam Generator Tubesheet-to-Channel Head Weld), and Category B-D, Item No. 83.11 O (Pressurizer Nozzle-to-Vessel Weld) on the basis that the ASME Code requirement is impractical.

2.0 REGULATORY REQUIREMENTS The licensee is requesting relief from the ASME BPV Code, Section XI, in accordance with 10 CFR 50.55a(g)(5)(iii). The ASME BPV Code Class 1, 2, and 3 components must meet the requirements of Section XI of the ASME BPV Code as required by 10 CFR 50.55a(g)(4), which states, in part, that:

Throughout the service life of a boiling or pressurized water-cooled nuclear power facility, components (including supports), that are classified as ASME Enclosure

Code Class 1, Class 2, and Class 3 must meet the requirements, except design and access provisions and preservice examination requirements, set forth in Section XI of editions and addenda of the ASME BPV Code ...

The licensee may request relief from portions of the ASME BPV Code as provided in 10 CFR 50.55a(g)(5)(iii), which states, in part, that:

If the licensee has determined that conformance with a Code requirement is impractical for its facility the licensee must notify the NRC [U.S. Nuclear Regulatory Commission] and submit, as specified in §50.4, information to support the determinations. Determinations of impracticality in accordance with this section must be based on the demonstrated limitations experienced when attempting to comply with the Code requirements during the inservice inspection interval for which the request is being submitted.

And, the NRC staff may grant relief from ASME BPV Code requirements as provided in 10 CFR 50.55a(g)(6)(i), which states that:

The Commission will evaluate determinations under paragraph (g)(5) of this section that code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines are authorized by law, will not endanger life or property or the common defense and security, and are 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.

Based on the above, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to request and the NRC to authorize the alternative requested by the licensee.

3.0 TECHNICAL EVALUATION

3.1 Component Affected The affected components are ASME Code Class 1 pressurizer and steam generator welds as identified in Table RR-3 of VEGP-ISI-RR-03.

• Category B-B, Item No. 82.11 Pressurizer Shell-to-Head Circumferential Weld

• Category B-B, Item No. B2.40 Steam Generator Tubesheet-to-Channel Head Weld

• Category B-D, Item No. B3.110 Pressurizer Nozzle-to-Vessel Weld 3.2 Applicable Code Edition and Addenda The code of record for the third 10-year ISi interval is Section XI of the 2001 Edition through 2003 Addenda of the ASME BPV Code.

3.3 Duration of Relief Request The licensee submitted this relief request for the third 10-year ISi interval that started on May 31, 2007, and ended on May 30, 2017.

3.4 ASME BPV Code Requirement The ASME BPV Code requirements applicable to the Class 1 welds originate in Table IWB-2500-1 of Section XI to the ASME BPV Code. For Examination Category 8-8 (Item No. 82.40), Table IWB-2500-1 requires volumetric examinations of pressure-retaining welds in the steam generator. The applicable examination volume is defined in ASME BPV Code, Section XI, Figure IWB-2500-6. For Examination Category 8-8 (Item No. 82.11) and Category 8-D (Item No. 83.110), Table IWB-2500-1 requires volumetric examinations of pressure-retaining welds in the pressurizer. The applicable examination volume is defined in ASME BPV Code, Section XI, Figures IWB-2500-1 and IWB-2500-?(b).

3.5 Impracticality of Compliance For the steam generator tubesheet-to-channel head weld (B-B/82.40), the licensee stated that a physical limitation due to the support leg(s) and identification plate obstructs and/or prohibits transducer movement along the required scan region of the channel head-to-tubesheet weld.

For pressurizer head circumferential welds (B-B/82.11 ), the licensee stated that the geometric limitations of the pressurizer supports, identification plates, and instrumentation nozzles obstruct and/or prevent transducer movement along the required scan region of the upper head-to-upper shell weld.

For pressurizer nozzle-to-head welds (B-D/83.110), the licensee stated that the geometric configuration of the 4 inch spray, 6 inch relief, and 14 inch surge nozzles prevents scanning from the nozzle side for the upper and lower nozzle-to-vessel welds.

Therefore, full ASME BPV Code coverage is not possible due to the obstructions for the first two items and the configuration of the nozzles for the third. The licensee stated that the burden caused by compliance includes the redesign and replacement of the steam generator and pressurizer nozzles and supports with nozzles of special design to allow examination.

3.6 Proposed Alternative and Bases for Relief The licensee stated that the inservice examinations of the steam generator and pressurizer welds are being conducted to the extent practical. Class 1 pressure boundary, pressure tests are performed in each refueling outage.

The licensee further stated that although there are physical obstructions which limit and/or prohibit the amount of examination coverage for those components identified in Table RR-3, reasonable assurance still exists that an acceptable level of quality and safety will be maintained. As a result, the licensee requests that relief be authorized pursuant to 10 CFR 50.55a(g)(6)(i) since it is impractical to perform the examinations as required by the ASME BPV Code.

3.7 NRC Staff Evaluation The NRC staff evaluated the affected pressurizer and steam generator welds in this relief request pursuant to 10 CFR 50.55a(g)(6)(i). The NRC staff's evaluation focused on: (1) if a technical justification exists to support the determination that the ASME BPV Code requirement is impractical; (2) that imposition of the ASME BPV Code required inspections would result in a burden to the licensee; and (3) that the licensee's reduced inspection coverage continues to

provide reasonable assurance of structural integrity and leak tightness of the subject welds.

The NRC staff finds that if these three criteria are met, the requirements of 10 CFR 50.55a(g)(6)(i) will also be met.

3. 7 .1 Impracticality of Compliance As described and demonstrated in the submittal (Figures RR-3-1 to RR-3-13), the affected welds can be divided into two groups: (1) head-to-shell and head-to-tube sheet welds and (2) nozzle-to-head.welds. The Group 1 welds have achieved coverages from 75 percent to 88 percent. The NRC staff examined Figures RR-3-1 to RR-3-5 and confirmed these coverages. The lowest coverage of 75 percent was caused by the curvature of the pressurizer head, the header supports, the welded pads, and instrument nozzles, adjacent to the subject circumferential weld. The Group 2 welds have achieved coverage from 15 percent to 55.9 percent. Likewise, the NRC staff examined Figures RR-3-6 to RR-3-13 and confirmed the coverages. Additionally, the predominant limitations that prevented the licensee's ultrasonic testing (UT) to achieve essentially 100 percent coverage of the Group 2 welds were the presence of the various nozzles that disallow access to the subject welds from the nozzle side.

The secondary limitations are due to the configuration of each nozzle. The lowest coverage of 15 percent for the pressurizer surge nozzle to head welds was caused by adjacent heater penetrations, in addition to the two limitations stated above. The drastic coverage difference for the surge nozzle to lower head weld between Vogtle, Unit 1 (44.6 percent), and Vogtle, Unit 2 (15 percent), is due to the much smaller transducer movement distance for Vogtle, Unit 2, in the direction perpendicular to the circumferential weld. Other Group 2 welds have approximately 50 percent coverage.

These coverages were obtained using Appendix VIII requirements of the 2001 Edition of the ASME BPV Code, Section XI, and applicable Electric Power Research Institute Performance Demonstration Initiative Program guidance and, therefore, represent best-effort UT results to the extent practical. This best effort to the extent practical is also supported by the increased coverages of 1.8, 4, 5.9, 7, and 29.6 percent for various components over what were achieved during the second ISi interval ("Vogtle Electric Generating Plant: Second Ten-Year Interval lnservice Inspection Program," dated May 29, 1997, ADAMS Legacy Accession No.

9706030146) due to improved UT equipment and transducers.

Based on the above evaluation, the NRC staff finds that achieving essentially 100 percent weld examination coverage is impractical.

3.7.2 Burden of Compliance The licensee stated that compliance would require the redesign and replacement of the steam generator and pressurizer nozzles and supports with nozzles of special design to allow full examination coverage, which would be a very large capital investment by the licensee. The NRC staff finds that replacing or reconfiguring the components of the subject welds to achieve full coverage constitutes a burden on the licensee.

3. 7 .3 Structural Integrity and Leak Tightness The NRC staff considered whether the licensee's proposed alternative provided reasonable assurance of structural integrity and leak tightness of the subject weld based on: (1) safety significance of unexamined volumes - unachievable coverage (e.g., any stress or the material condition of the welds, indicating that the uncovered areas are more susceptible to cracking or

degradation), and (2) operating experience supporting structural integrity and leak tightness.

For the safety significance of the unexamined volumes of welds, the NRC staff reviewed the sketches in the submittal (Figures RR-3-1 to RR-3-13) and the information provided in the supplement dated September 26, 2018:

For the 4" [inch] Spray Nozzles and 14" [inch] Surge Nozzles, the stress report shows a lower stress ratio going toward the nozzle.

The NRC staff examined the attached UT coverage plot and verified that part of the highly stressed areas were within the UT coverage.

For the 6" [inch] Safety and Relief Valve Nozzles, the design stress ratio is slightly higher in the area of limited UT scanning.

• Since the inspection results are unlikely to be affected by a small difference in stresses, the NRC staff determined that the inspection results of each component represent the entire weld. Therefore, the NRC staff finds that if significant service induced degradation had occurred, evidence of it would have been detected by the licensee-performed examinations.

• The licensee confirmed that the SNC fleet operating experience, including the Vogtle units, indicated no leakage or indications that require flaw evaluations or repairs for the subject welds.

In addition, the licensee stated that Class 1 pressure boundary, pressure tests are performed each refueling outage. Pressure tests will provide additional assurance that any through-wall cracking, if present, would be detected and the licensee will take appropriate corrective actions.

Therefore, the NRC staff finds that the UT examinations performed provide reasonable assurance of structural integrity and leak tightness of the subject welds.

4.0 CONCLUSION

As set forth above, the NRC staff finds that it is impractical for the licensee to comply with the ASME BPV Code, Section XI, requirement; that the proposed inspection provides reasonable assurance of structural integrity or leak tightness of the subject welds; and 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. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(6)(i). Therefore, the NRC staff grants relief request VEGP-ISI-RR-03 for Vogtle, Units 1 and 2, for the third 10-year ISi interval, which commenced on May 31, 2007, and ended on May 30, 2017.

All other ASME BPV Code, Section XI, requirements for which relief was not specifically requested and authorized herein by the NRC staff remain applicable, including the third party review by the Authorized Nuclear lnservice Inspector.

Principal Contributor: S. Sheng, NRR

C. A. Gayheart

SUBJECT:

VOGTLE ELECTRIC GENERATING PLANT, UNITS 1 AND 2 - RELIEF REQUEST REGARDING EXAMINATION COVERAGE FOR CERTAIN PRESSURIZER AND STEAM GENERATOR WELDS (VEGP-ISI-RR-03)

(EPID L-2018-LLR-0075) DATED OCTOBER 31, 2018 DISTRIBUTION:

PUBLIC RidsNrrKGoldstein Resource RidsNrrPMVogtle Resource RidsRgn2MailCenter Resource RidsACRS_MailCTR Resource SSheng, NRR RidsNrrDorlLpl2 1 Resource ADAMS Access1on No.: ML18296A717 *B1y e-ma1*1 OFFICE N RR/DORL/LPL2-1 /PM NRR/DORL/LPL2-1 /LA NRR/DE/EVIB/BC* NRR/DORL/LPL2-1/BC NAME MOrenak KGoldstein DAIiey MMarkley DATE 10/26/18 10/25/18 10/11/18 10/31/18 OFFICIAL RECORD COPY