ML19143A342

Inservice Inspection Alternative Request N2-I4-LMT-003

ML19143A342
Person / Time
Site:	North Anna
Issue date:	05/29/2019
From:	Markley M Plant Licensing Branch II
To:	Stoddard D Virginia Electric & Power Co (VEPCO)
Hall J
References
EPID L-2019-LLR-0000
Download: ML19143A342 (11)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 May 29, 2019 Mr. Daniel G. Stoddard Senior Vice President and Chief Nuclear Officer Innsbrook Technical Center 5000 Dominion Blvd.

Glen Allen, VA 23060-6711

SUBJECT:

NORTH ANNA POWER STATION, UNIT NO. 2 - INSERVICE INSPECTION ALTERNATIVE REQUEST N2-14-LMT-003 (EPID L-2019-LLR-OOOO)

Dear Mr. Stoddard:

By letter dated December 20, 2018 (Agencywide Documents Access and Management System Accession No. ML18361A648), the Virginia Electric and Power Company (Dominion, the licensee) submitted a relief request for the North Anna Power Station (North Anna), Unit No. 2. The requested relief, pursuant to 10 CFR 50.55a(g)(5)(iii), would allow the performance of limited coverage examinations for certain welds during the fourth 10-year inservice inspection (ISi) interval for North Anna, Unit No. 2, in lieu of the full coverage examinations required by the applicable edition of the ASME Code.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that it is impractical for the licensee to comply with the requirements of the ASME Code,Section XI, for the examinations of the components noted in Relief Request (RR) N2-14-LMT-003 for North Anna, Unit No. 2. The NRC staff further concludes that the proposed examinations provide reasonable assurance of structural integrity or leak tightness of the subject welds, and that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii). Accordingly, the NRC staff has determined that the granting of relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property or 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, the NRC staff grants the use of RR N2-J4-LMT-003, for North Anna, Unit No. 2, for the fourth 10-year ISi interval, which began on December 14, 2010 and is scheduled to end on December 13, 2020.

All other ASME 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.

D. Stoddard If you have any questions, please contact the Project Manager, Randy Hall, at 301-415-4032 or via e-mail at Randy.Hall@nrc.gov.

Sincerely,

~-Z.k~

Michael T. Markley, Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-339

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 N2-14-LMT-003 REGARDING EXAMINATION COVERAGE FOR PRESSURIZER NOZZLE-TO-VESSEL WELDS VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION, UNIT NO. 2 DOCKET NO. 50-339

1.0 INTRODUCTION

By letter dated December 20, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18361A648), Virginia Electric and Power Company (Dominion Energy Virginia or the licensee) requested relief from certain requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components." This relief request, N2 LMT-003, pertains to the examinations performed on the pressurizer nozzle-to-vessel welds and certain piping welds covered by the licensee's Risk-informed ISi program during the fourth inservice inspection (ISi) interval, at the North Anna Power Station (North Anna), Unit No. 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, if necessary, for inspection of Category B-D, "Full Penetration Welded Nozzles in Vessels," Item No. B3.110 (Pressurizer Nozzle-to-Vessel Welds), and Category R-A, "Risk-Informed Piping Examinations," Item No. R1 .20 (Elements Not Subject to a Degradation Mechanism), on the basis that the ASME Code requirements are impractical.

2.0 REGULATORY EVALUATION

Pursuant to 10 CFR 50.55a(g)( 4 ), lnservice inspection standards requirement for operating plants, throughout the service life of a boiling or pressurized water-cooled nuclear power facility, components (including supports) that are classified as ASME 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 Code that become effective subsequent to editions specified in 10 CFR 50.55a(g)(2) and (3) and that are incorporated by reference in paragraph 10 CFR 50.55a(a)(1 )(ii), to the extent practical within the limitations of design, geometry, and materials of construction of the components.

Pursuant to 10 CFR 50.55a(g)(5)(iii), ISi program update: Notification of impractical ISi Code requirements, if the licensee has determined that conformance with the ASME Code Enclosure

requirement is impractical for its facility, the licensee must notify the U.S. Nuclear Regulatory Commission (NRC) and submit, as specified in 10 CFR 50.4, information to support the determination. Determinations of impracticality in accordance with 10 CFR 50.55a must be based on the demonstrated limitations experienced when attempting to comply with the Code requirements during the ISi interval for which the request is being submitted. Requests for relief made in accordance with 10 CFR 50.55a must be submitted to the NRC no later than 12 months after the expiration of the initial or subsequent 120-month inspection interval for which relief is sought.

Pursuant to 10 CFR 50.55a(g)(6)(i), Impractical ISi requirements: Granting of relief, the Commission will evaluate determinations under paragraph (g)(S) of 10 CFR 50.55a that ASME Code requirements are impractical. The Commission may grant such relief and may impose such alternative requirements as it determines are authorized by law, and 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 grant the relief requested by the licensee.

3.0 TECHNICAL EVALUATION

The pressurizer nozzle-to-vessel welds and the risk-informed piping welds not subject to a degradation mechanism were addressed in separate sections of Relief Request (RR)

N2-14-LMT-003 (Sections A 1 and R1, respectively). Similarly, Section 3.1 of this safety evaluation (SE) addresses the pressurizer nozzle-to-vessel welds, and Section 3.2 addresses the specified piping welds.

• 3.1 Pressurizer Nozzle-to-Vessel Welds 3.1.1 Components Affected The affected components are ASME Code Class 1 component welds as identified in Table 1 of RR N2-14-LMT-003.

Category: B-D, "Full Penetration Welded Nozzles in Vessels" Item No.: 83.110, "Pressurizer Nozzle-to-Vessel Welds" Component ID: 12050-WMKS-RC-E-2/2-RC-E-2/11 (Weld 11) 12050-WMKS-RC-E-2/2-RC-E-2/12 (Weld 12) 12050-WMKS-RC-E-2/2-RC-E-2/13 (Weld 13) 3.1.2 Applicable Code Edition and Addenda The code of record for the fourth 10-year ISi interval is the 2004 Edition of the ASME Code with no Addenda .

3.1.3 ASME Code Requirement ASME Code,Section XI, Table IWB-2500-1, Examination Category B-D, Item B3.110 requires a 100 percent volumetric examination of the pressurizer nozzle-to-vessel welds, as depicted in Figure IWB-2500-7.

3.1.4 Impracticality of Compliance Welds 11 and 12 on the safety valve nozzles are limited to 67 .6 percent due to nozzle geometry associated with the nozzle bend radius and due to cladding preventing extended V-path.

Enclosures A1-1 and A1-2 of the submittal support the coverage determination based on the limitations experienced.

• Although different inspection coverages for these welds have been reported for the third interval (Relief Request N2-13-PRT-002-A5; ADAMS Accession No. ML12227A773) and the second interval (Relief Request NDE-28, dated October 10, 1996),

they are attributed to different guidelines for calculating coverage.

Weld 13 on the relief nozzle was limited to 67.6 percent examination coverage due to nozzle geometry associated with the nozzle-to-pressurizer head transition . The angle between the nozzle and the pressurizer head is not perpendicular, limiting search unit manipulation particularly at the intrados angle. Enclosure A 1-3 of the submittal supports the coverage determination based on the limitations experienced . Again, the licensee attributes the different inspection coverages for Weld 13 reported for the third interval (Relief Request N2-13-PRT-002-A5; ADAMS Accession No. ML12227A773) and the second interval (Relief Request NDE-43 dated November 21 , 2000) to different guidelines for calculating coverage.

The licensee stated that in order to effectively increase the examination coverage, the nozzle-to-vessel welds would require design modification or replacement.

3.1.5 Proposed Alternative and Basis for Relief No alternative examination is proposed because the licensee believes that: ( 1) the volumetric examinations performed should detect any degradation that may occur in the areas covered and provide reasonable assurance of the structural integrity of the subject welds, and (2) the physical configuration of each nozzle limits the effectiveness of alternative or advanced technologies from increasing the examination coverage for this configuration .

The licensee also states that no recordable indications were identified during these examinations.

3.1.6 Duration of Relief Request The licensee submitted this relief request for the fourth 10-year ISi interval at North Anna, Unit No. 2, which started on December 14, 2010, and will end on December 13, 2020.

3.1. 7 NRC Staff Evaluation ASME Code,Section XI, Table IWB-2500-1, Examination Category B-D, Item B3.11 O requires a 100 percent volumetric examination of the support (Figure IWB-2500-7). The applicable component is the pressurizer nozzle-to-vessel welds; Welds 11, 12, and 13.

The NRC staff has evaluated the affected pressurizer nozzle-to-vessel welds in this relief request pursuant to 10 CFR 50.55a(g)(6)(i). The NRC staff's evaluation focused on whether:

(1) a technical justification exists to support the determination that the ASME Code requirement is impractical; (2) imposition of the Code required inspections would result in a burden to the licensee; and (3) the licensee's proposed alternative (accepting the reduced inspection coverage in this case) provides reasonable assurance of structural integrity and leak tightness of the subject welds. The NRC staff finds that if these three criteria are met, then the requirements of 10 CFR 50.55a(g)(6)(i) will also be met.

Impracticality of Compliance As described in the submittal, the coverage of Welds 11 and 12 of the pressurizer safety valve nozzles is limited to 67.6 percent due to nozzle geometry associated with the nozzle bend radius and due to cladding preventing the extended V-path of the ultrasonic {UT) scan. The coverage of Weld 13 of the relief valve nozzle is limited to 67.6 percent due to nozzle geometry associated with the nozzle-to-pressurizer head transition. The NRC staff examined sketches for Weld 11 in Enclosure A 1-1 of the relief request, sketches for Weld 12 in Enclosure A 1-2, and sketches for Weld 13 in Enclosure A 1-3. This review confirmed that, for all three welds, the UT scans from the nozzle side were severely limited due to nozzle and pressurizer vessel geometry. As a result, the average coverage for each of these welds did not meet the ASME Code,Section XI requirements.

Based on the above evaluation, the NRC staff finds that a technical justification exists to support the determination that achieving essentially 100 percent coverage is impractical.

Burden of compliance The licensee stated that in order to effectively increase the examination coverage, the nozzle-to-vessel welds would require design modifications or replacement. Considering the coverage plots of the subject welded components in Enclosures A 1-1, A 1-2, and A 1-3, the NRC staff also finds that design modification or replacement of the welds is required to increase examination coverage. Therefore, the NRC staff finds that replacing or reconfiguring the components to achieve full coverage constitutes a burden on the licensee.

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 component welds based on:

(1) the safety significance of unexamined volumes or 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 noted that the figures in Enclosures A 1-1, A 1-2, and A 1-3 indicated that the coverage of 67.6 percent is based on the average of the cross-section coverages from different beam angles and approaching sides of each of the three circumferential welds, and, therefore, remains a constant value circumferentially. This means that the area of the highest stresses (due to pressure, thermal, weld residual, and piping loads) and the worst material properties (due to weld repair or fabrication defects) would always be adjacent to or in the UT covered area. Consequently, it is reasonable to conclude that the safety significance of potential degradation in the unexamined

volumes of welds is minimal, and, if significant service induced degradation had occurred, evidence of it would have been detected by the examinations that the licensee already performed for the subject components. The licensee stated that no recordable indications were identified during these examinations.

In addition, pressure tests performed by the licensee in accordance with the ASME Code,Section XI will provide additional assurance that any through-wall cracking, if it occurred , would be detecte~ 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.

3.2 Risk-Informed Piping Welds Not Subject to a Degradation Mechanism The NRC staff evaluated the information in the licensee's submittal for the RI-ISi piping welds in RR N2-14-LMT-003 and documented its findings below.

3.2.1 Components Affected Details of the welds .under Examination Category R-A are shown in Table 1 of this SE and were obtained from Table 1 of the attachment of the licensee's submittal.

Table 1. Examination Category R-A Limited Volumetric Examination Coverage Weld Material; Percent Weld Examination Item No. Component Coverage Identification Limitation Description Achieved Carbon steel; Main Feedwater Isolation Pipe to Weldolet 5 (BPL-851)

R1.20 Valve Bypass design . No scan 42.2 6"-WFPD-411 Piping 6" NPS on weldolet side Weldolet SCH 80 Carbon steel; Main Feedwater Isolation Pipe to Weldolet SW-19 (BPL 178)

R1 .20 Valve Bypass design. No scan 75 6"-WFPD-415 Piping 6" NPS on weldolet side Weldolet SCH 80 Stainless steel; Elbow to Pump Reactor Coolant 20 Casing design R1.20 System Piping- 88 31"-RC-405 configuration Elbow to Pump limits scans Casing Stainless steel; Pipe to Flange SW-98A 1.5" NPS SCH 160 design R1.20 50 1.5"-CH-797 Charging System configuration Piping limitation

Weld Material; Percent Weld Examination Item No. Component Coverage Identification Limitation Description Achieved Stainless steel; Pipe to Flange SW-81 1.5" NPS SCH 160 design R1.20 50 1.5"-CH-798 Charging System configuration Piping limitation Stainless steel; Tee to Reducer Tee to Reducer 30 design R1.20 Reactor Coolant 81 2"-RC-456 configuration System Sampling limitation Line Stainless steel; Expander to 3 Expander to Elbow Elbow design R1.20 88.5 4"-CH-815 Charging System configuration Piping limitation 3.2.2 Applicable ASME Code Edition and Addenda The ASME Code of record at NAPS 2 for the fourth 10-year ISi interval was the 2004 Edition of ASME Code,Section XI with no Addenda, at the time these exams were performed.

3.2.3 ASME Code Requirement The volumetric examination requirement for Examination Category R-A, Item R1 .20, per Table 1 of ASME Code Case N-716 is "essentially 100 percent. " The licensee has cited ASME Code Case N-460, "Alternative Examination Coverage for Class 1 and Class 2 Welds,Section XI, Division 1," which defines "essentially 100 percent" as greater than 90 percent coverage of the examination volume or surface area, as applicable. ASME Code Case N-460 is an alternative approved for use by the NRC in Regulatory Guide 1.147, Revision 18, "lnservice Inspection Code Case Acceptability," (ADAMS Accession No. ML16321A336).

3.2.4 Impracticality of Compliance The licensee achieved the volumetric coverage shown in Table 1 of this SE for the subject welds and could not achieve the ASME Code required examination coverage because of the examination limitations shown. For the seven piping welds in Table 1, the licensee achieved 42.2 to 88.5 percent of the required examination volume and did not detect any recordable indications. The licensee indicated that due to the physical limitations listed in

Table 1 of this SE, complying with the ASME Code required examination coverage is impractical and is thus requesting relief pursuant to 10 CFR 50.55a(g)(5)(iii).

3.2.5 Proposed Alternative and Basis for Relief The licensee indicated that the required examination coverage can only be accomplished by modifying and/or replacing the components associated with the reduced examination coverage and therefore presents a burden for compliance. In lieu of the ASME Code required examination coverage, the licensee examined these welds to the maximum extent practical, achieving the coverages shown in Table 1. The volumetric examinations were performed in accordance with Section XI, Mandatory Appendix I, 1-2220, which implements the Appendix VIII, Performance Demonstration Program for ultrasonic examinations.

3.2.6 Duration of Relief Request The licensee submitted RR N2-14-LMT-003 for the fourth 10-year ISi interval at North Anna, Unit No. 2, which began on December 14, 2010, and is scheduled to end on December 13, 2020.

3.2. 7 NRC Staff Evaluation For the Examination Category R-A welds listed in Table 1 of this SE, the licensee achieved less than the required volumetric examination coverage due to geometric, material, and physical limitations that would entail modification or replacement of the associated components if the required coverage were to be obtained. The NRC staff finds the stated limitations to be an acceptable basis for impracticality of conforming to the requirements and finds that the design modifications necessary to achieve the required coverage would constitute a burden upon the licensee.

With the exception of Weld 20, the licensee examined the subject welds using manual UT examination methods in accordance with ASME Code Section XI, Appendix VIII, Performance Demonstration Program to achieve the UT examination coverages shown in Table 1. For Weld 20, the licensee performed the UT examination in accordance with ASME Section V, Article 4, ASME Section XI, Appendix Ill, and the associated Mandatory Supplements.

The licensee used a combination of 45-degree, 60-degree, and 70-degree shear wave as well as 0-degree, 45-degree, and 60-degree longitudinal scanner, parallel and transverse to the weld, and because of the noted limitations, was not able to achieve the required examination volumes for the subject welds.

The NRC staff reviewed the examination coverage and verified the licensee's achieved coverage. The NRC staff finds the licensee's achieved coverages acceptable, given the noted limitations. The examined volumes included weld and base metal in the inner region where degradation is expected to show, should it occur.

For Welds 5 and SW-10, due to the noted limitations, the licensee was able to achieve 42.2 and 75 percent of the required examination volume with no reportable indications. Additionally, the licensee performed augmented magnetic particle examinations on these welds, again with no recordable indications.

For Welds 20, 30, and 3, the licensee's examinations achieved 88, 81, and 88.5 percent of the required examination coverage, respectively, with no recordable indications. Additionally, it is

noted that these locations receive a visua.1examination during the system leakage tests performed at the end of each refueling outage. Furthermore, these locations are also subject to visual examinations at the beginning of each refueling outage as part of licensee's Boric Acid Corrosion Control Program.

• Based on the above, the NRC staff determined that obtaining the ASME Code required examination volume coverage for the welds listed in Table 1 is impractical because of the stated limitations and that the modifications necessary to obtain the required coverage would impose a burden upon the licensee. The NRC staff also determined that the volumetric UT examinations performed to the maximum extent practical provides reasonable assurance of the structural integrity of the subject welds because: (1) the licensee identified no recordable* indications; (2) evidence of significant service-induced degradation in the welds, if it were to occur, would likely have been detected by the volumetric examination coverage obtained by the licensee; (3) the examined weld volume includes the most susceptible regions, is the same material as the unexamined volume, is under the same loading conditions, and is exposed to the same environment; and (4) for Welds 5 and SW-10, which are not subject to the Boric Acid Program and the system leakage tests, the applicant performed augmented surface examinations to confirm the structural integrity of the welds.

3.0 CONCLUSION

As set forth above, the NRC staff concludes that it is impractical for the licensee to comply with the requirements of the ASME Code,Section XI, for the examinations of the components noted in RR N2-14-LMT-003 for North Anna , Unit No. 2. The NRC staff further concludes that the proposed examinations provide reasonable assurance of structural integrity or leak tightness of the subject welds, and that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(g)(5)(iii). Accordingly, the NRC staff has determined that the granting of relief pursuant to 10 CFR 50.55a(g)(6)(i) is authorized by law and will not endanger life or property or 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, the NRC staff grants the use of RR N2-14-LMT-003, for North Anna, Unit No. 2, for the fourth 10-year ISi interval, which began on December 14, 2010, and is scheduled to end on December 13, 2020.

All other ASME 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 Contributors: S. Sheng, NRR R. Kalikian, NRR Date: May 29, 2019

ML19143A342 *via email OFFICE DORL/LPLll-1/PM DORL/LP LI 1-1 /LA DMLR/MVIB/BC*

NAME JRHall KGoldstein DAIiey DATE 05/28/19 05/28/19 03/22/19 OFFICE DMLR/MPHB/BC(A)* DORL/LPLll-1 /BC DORL/LP LI 1-1 /PM NAME SCumblidge MMarkley JRHall DATE 05/21/19 05/29/19 05/29/19