ML19140A288
| ML19140A288 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 05/28/2019 |
| From: | Markley M Plant Licensing Branch II |
| To: | Stoddard D Virginia Electric & Power Co (VEPCO) |
| Hall J | |
| References | |
| EPID L-2018-LLR-0113 | |
| Download: ML19140A288 (9) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 May 28, 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 NOS. 1 AND 2 - INSERVICE INSPECTION ALTERNATIVE REQUESTS N1-15-CMP-001 AND N2-15-CMP-001 (EPID L-2018-LLR-0113)
Dear Mr. Stoddard:
By letter dated August 15, 2018 (Agencywide Documents Access and Management System Accession (ADAMS) No. ML18234A133), Virginia Electric and Power Company (the licensee) submitted a request for a proposed alternative to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, to the U.S. Nuclear Regulatory Commission (NRC) for the North Anna Power Station (North Anna),
Unit Nos. 1 and 2. Pursuant to Title 10 of the Code of Federal Regulations (10 CFR}, Part 50, Paragraph 55a(z)(1 ), the licensee requested the NRC to authorize the use of the encoded phased array ultrasonic testing technique in lieu of radiographic testing to perform the volumetric examinations of the ferritic or austenitic piping welds during repair/replacement activities, on the basis that the proposed alternative provides an acceptable level of quality and safety.
The NRC staff has reviewed the subject request and concludes, as set forth in the enclosed safety evaluation, that the licensee's proposed alternative provides an acceptable level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(z)( 1). Therefore, the NRC staff authorizes the use of the proposed alternative in N1-15-CMP-001 for the remainder of the fifth 10-year inservice inspection (ISi) interval at North Anna, Unit No. 1, and N2-15-CMP-001 for the fifth 10-year ISi interval and the remainder of the fourth interval at North Anna, Unit No. 2.
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, Michael T. Markley, Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-338 and 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 REQUESTS N1-15-CMP-001 AND N2-15-CMP-001 REGARDING USE OF ENCODED PHASED ARRAY ULTRASONIC TESTING IN LIEU OF RADIOGRAPHIC TESTING FOR FERRITIC OR AUSTENITIC PIPING WELDS VIRGINIA ELECTRIC AND POWER COMPANY {DOMINION ENERGY VIRGINIA)
NORTH ANNA POWER STATION, UNIT NOS. 1 AND 2 DOCKET NOS. 50-338 AND 50-339
1.0 INTRODUCTION
By letter dated August 15, 2018 (Agencywide Documents and Access Management System (ADAMS) Accession No. ML18234A133), Virginia Electric and Power Company (the licensee) requested relief from certain requirement of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, IWA-4000. In relief requests N1-15-CMP-001 and N2-15-CMP-001, the licensee proposed to utilize the encoded phased array ultrasonic testing (PAUT) technique in lieu of radiographic testing (RT) to perform the volumetric examinations of the ferritic or austenitic piping welds during repair/replacement activities. Relief requests N1-15-CMP-001 and N2-15-CMP-001 are for the North Anna Power Station, (North Anna), Units 1 and 2, respectively.
Specifically, pursuant to Title 10 of the Code of Federal Regulations ( 10 CFR) 50.55a(z)( 1), the licensee requested to use the proposed alternative on the basis that the alternative would provide an acceptable level of quality and safety.
2.0 REGULATORY EVALUATION
Pursuant to 10 CFR 50.55a(g)(4), lnservice Inspection Standards Requirement for Operating Plants, Components (including supports) that are classified as ASME Code Class 1, Class 2, and Class 3 must meet the requirements in 50.55a throughout the service life of a boiling or pressurized water-reactor (BWR or PWR). The exception is the 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 paragraphs (g)(2) and (3) of 50.55a, which are incorporated by reference in paragraph (a)(1 )(ii) of 50.55a to the extent practical within the limitations of design, geometry, and materials of construction of the components.
Enclosure
Pursuant to 10 CFR 50.55a(g)(4)(ii), Applicable ISi Code: Successive 120-month Intervals, inservice examination of components and system pressure tests conducted during successive 120-month inspection intervals must comply with the requirements of the latest edition and addenda of the ASME Code incorporated by reference in paragraph (a) of 50.55a 12 months before the start of the 120-month inspection interval (or the optional ASME Code Cases listed in NRC Regulatory Guide (RG) 1.147, when using ASME Code,Section XI, as incorporated by reference in paragraph (a)(3)(ii) of 50.55a), subject to the conditions listed in paragraph (b) of 50.55a.
Pursuant to 10 CFR 50.55a(z), Alternatives to Codes and Standards Requirements, alternatives to the requirements of paragraphs (b) through (h) of 50.55a or portions thereof may be used when authorized by the Director, Office of Nuclear Reactor Regulation, or Director, Office of New Reactors, as appropriate. A proposed alternative must be submitted and authorized prior to implementation. The applicant or licensee must demonstrate that: (1) Acceptable Level of Quality and Safety, the proposed alternative would provide an acceptable level of quality and safety; or (2) Hardship without a Compensating Increase in Quality and Safety, compliance with the specified requirements of 50.55a would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
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 ASME Code,Section XI, piping welds made of the ferritic steel or austenitic stainless steel that require radiography as part of a repair/replacement activities are affected.
3.2 Applicable Code Edition and Addenda - Duration of Relief Request 10-Year Duration of Relief Request ASME Code of Plant ISi Interval is Record Interval Started Interval Scheduled to End North Anna, 5th 2013 Edition May 1, 2019 April 30, 2029 Unit 1 North Anna, 4th 2004 Edition December 14, 2010 December 13, 2020 Unit 2 North Anna, 5th 2013 Edition December 14, 2020 December 13, 2030 Unit 2 3.3 ASME Code Requirement The ASME Code requirements applicable to repair/replacement activities originate in IWA-4000 of Section XI.
Paragraph IWA-4221 of the 2013 Edition of the ASME Code,Section XI, requires that items used for repair/replacement activities meet the applicable Construction Code requirements when performing repair/replacement activities. Paragraph IWA-4520(b) of the 2013 Edition of the ASME Code,Section XI, allows the Owner to authorize use of ultrasonic examination in
place of radiographic examination if the conditions of IWA-4521 are met. However, the regulation in 10 CFR50.55a(b)(2)(xix) does not approve the IWA-4520(b)(2) and IWA-4521 substitution of ultrasonic examination for radiographic examination.
Paragraph IWA-4221 of the 2004 Edition of the ASME Code,Section XI, requires that items used for repair/replacement activities meet the applicable Owner's Requirements and Construction Code requirements when performing repair/replacement activities.
Paragraph IWA-4520 of the 2004 Edition of the ASME Code,Section XI, requires that welded joints made for installation of items be examined in accordance with the Construction Code identified in the Repair/Replacement Plan.
3.4 Proposed Alternative The licensee proposed to use the encoded PAUT technique in lieu of the ASME Code required RT to perform the volumetric examinations of the ferritic steel or austenitic stainless steel piping weld during repair/replacement activities. The licensee's proposed alternative requirements are documented in Section 5 of N1-15-CMP-001 and N2-15-CMP-001.
3.5 Basis for Use of Alternative The licensee stated that the use of the proposed encoded PAUT for the volumetric examinations of ferritic or austenitic piping repair/replacement welds would eliminate the safety risk associated with the use of the Code required RT, which includes both planned and unplanned radiation exposure to plant workers. In addition, the use of the encoded PAUT significantly minimizes the impact on other outage activities as compared to the use of RT.
The licensee stated that the basis for proposed encoded PAUT in lieu of RT for the ferritic or austenitic welds was developed from numerous codes, code cases, associated industry experience, articles, and the results of volumetric examinations conducted by the RT and encoded PAUT techniques. The encoded PAUT is equivalent or superior to the Code required RT for detecting and sizing critical (planar) flaws such as cracks and lack of fusion. The encoded PAUT provides sizing capabilities for both depth and length dimensions of the flaw, which are required to apply the applicable acceptance criteria of the ASME Code,Section XI.
However, RT does not provide the depth of a detected flaw.
The licensee stated that the encoded PAUT procedures, equipment, and personnel are qualified by the performance demonstration in accordance with requirements in Section 5 of N1-15-CMP--01 and N2-15-CMP-001 using representative piping conditions and flaws that demonstrate the ability to detect and size flaws that are both acceptable and unacceptable to the defined acceptance standards.
3.6 NRC Staff Evaluation The NRC staff has evaluated relief requests N1-15-CMP-001 and N2-15-CMP-001 pursuant to 10 CFR 50.55a(z)(1 ), that the proposed alternative provides an acceptable level of quality and safety. In evaluating the licensee's proposed alternative, the NRC staff focused on the following aspects of the licensee's basis: (1) effectiveness of encoded PAUT on the repair/replacement weld inspection; and (2) assurance of detection of structurally-significant fabrication flaws in ferritic steel or austenitic stainless steel piping weld by encoded PAUT. The NRC staff finds that if these two criteria are met, that the proposed alternative provides an acceptable level of quality and safety.
For its review, the NRC staff utilized NRC NUREG/CR-7204, "Applying Ultrasonic Testing In Lieu of Radiography for Volumetric Examination of Carbon Steel Piping," published in September 2015 (ADAMS Accession No. ML15253A674); and ASME Code Case N-831 "Ultrasonic Examination in Lieu of Radiography for Welds in Ferritic Pipe,Section XI," as a guidance. ASME Code Case N-831 has been incorporated by reference into the NRC proposed rule in Federal Register Notice 83 FR 40685, dated August 16, 2018, by inclusion in draft NRC Regulatory Guide 1.147, Revision 19 (DG-1342) with a condition that prohibits its use on new reactor construction.
Effectiveness of Encoded PAUT in lieu of RT for Repair/Replacement Weld Inspection Since 2009, the NRC staff has been assessing the effectiveness of use of ultrasonic testing (UT) techniques in lieu of RT techniques through literature reviews, detailed evaluations of previous relief requests, and confirmatory experimental work to validate findings. While each technique is capable to detect a spectrum of flaws resulting from fabrication welding processes, the differences in physical/material interactions can make one technique more sensitive to certain fabrication flaw types than the other technique. In NRC NUREG/CR-7204, the NRC concluded that the encoded PAUT technique as compared to RT provides an equally effective examination for identifying the presence of fabrication flaws in the ferritic steel piping welds; however, the encoded PAUT is more effective for detection of planar flaws than small volumetric flaws (i.e., volumetric flaws with less than 0.15 inch in diameter which are acceptable by the Construction Code). Based on this assessment, the NRC staff finds that there is a sufficient technical basis for use of PAUT technique in lieu of RT for the repair/replacement weld inspection.
Electric Power Research Institute (EPRI) published Technical Report (TP) No. 3002010297 "Technical Basis for Substituting Ultrasonic Testing for Radiographic Testing for New, Repaired, and Replacement Welds for ASME Section XI, Division 1, Stainless Steel Piping" in June 2017.
The report summarizes EPRl's performance-based approach based on ASME Code,Section X, Appendix VIII, to demonstrate the effectiveness of the encoded PAUT for detection and sizing the fabrication flaws in the austenitic stainless steel piping welds. Mockups containing representative welding fabrication flaws were fabricated for the performance demonstration.
The flaw distribution included both rejectable and acceptable sized flaws in accordance with the acceptance standards of IWB-3514 and flaw characterization figures of IWA-3300 of the ASME Code,Section XI. The performance demonstration initiative (PDI) generic procedures PDI-UT-2 and PDI-UT-3 were utilized for examination and flaw sizing. EPRI showed that (1) the encoded PAUT is an effective technique as compared to RT for detection and sizing fabrication flaws within the ferritic steel or austenitic stainless steel welds, and (2) the ASME Code,Section XI, Appendix VIII, root mean square error (RMSE) criteria for flaw length and depth sizing was met.
It is worth noting that there is a discrepancy between the equations for calculating the RMSE in ASME Code Section XI Appendix VIII Subparagraph Vlll-3120(d) and the submittal. The equation for determining the RMSE in the submittal has a typographical error, and the equation for calculating RMSE described in Section XI Appendix Vlll-3120(d) is accurate and should be used.
Based on the above, the NRC staff finds that there is a sufficient technical basis for the use of encoded PAUT in lieu of RT for repair/replacement inspection of the ferritic steel or austenitic stainless steel piping welds. The encoded PAUT as compared to RT was shown to be an effective technique for both detection and characterization of fabrication flaws in the repaired/replaced ferritic steel or austenitic stainless steel piping welds.
Assurance of Detection of Structurally-Significant Fabrication Flaws In evaluating the licensee's proposed alternative requirements, the NRC staff assessed the adequacy of the following aspects of the licensee's technical basis which include the performance demonstration and qualification of the encoded PAUT, achieving 100 percent coverage of the examination volume, and flaw acceptance criteria. The NRC staff verified that:
- The licensee will examine 100 percent of the weld volume and the weld-to-base-metal interface.
- The licensee will perform the encoded PAUT using the procedures, equipment, and personnel qualified by performance demonstration.
o The procedures will be demonstrated by using either a blind test or a nonblind test. The demonstration specimen set will include a minimum of 30 flaws covering a range of sizes, positions, orientations, and types of fabrication flaws.
The demonstration set will include specimens to represent the minimum and maximum diameter and thickness covered by the procedure.
o Personnel will be qualified for detection and sizing fabrication flaws by performance demonstration using the qualified procedure. The personnel performance demonstration will be conducted using a blind test (i.e., the flaw information is not provided). The demonstration specimen set will contain at least 1O flaws covering a range of sizes, positions, orientations, and types of fabrication flaws.
o The demonstration specimens will include both planar and volumetric fabrication flaws (e.g., lack of fusion, crack, incomplete penetration, slag inclusions) representative of welding process. The flaws will be distributed throughout the examination volume. The flaw through-wall heights for the performance demonstration will be based on the preservice acceptance standards for volumetric examination in accordance with ASME Code,Section XI, IWB-3400, IWC-3400, or IWD-3400, as applicable. At least 30 percent of the flaws will be classified as acceptable planar flaws, with the smallest flaws being at least 50 percent of the maximum allowable size based on the applicable aspect ratio for the flaw.
o Personnel will be qualified for flaw length sizing when the RMSE of the flaw lengths estimated by ultrasonic examinations, as compared with the true lengths, do not exceed 0.25 inch for nominal pipe size (NPS) 6 inches and smaller, and
- 0. 75 inch for larger than NPS 6 inches.
o Personnel will be qualified for flaw through-wall height sizing when the RMSE of the flaw through-wall heights estimated by ultrasonic examinations, as compared with the true through-wall heights, do not exceed 0.125 inch.
- The licensee will treat all flaws detected using angle-beam ultrasonic inspections as planar flaws and will evaluate the flaws against the preservice acceptance standards in ASME Code,Section XI, IWB-3400, IWC-3400, or IWD-3400, as applicable.
- The licensee will store the electronic data files for the encoded PAUT as archival-quality records permitting off-line analysis of images built from the data.
Therefore, the NRC staff finds that licensee's proposed performance demonstration for the encoded PAUT which includes procedures demonstration and personnel qualification are adequate because they are either consistent with or exceed the provisions in ASME Code,Section XI, Appendix VIII, for the ferritic steel or austenitic stainless steel piping welds.
In addition, the NRC staff notes that while IWB-3400, IWC-3400, and IWD-3400 of Section XI, the ASME Code allows larger flaws to remain inservice than that of NB-5330, NC-5330, and ND-5330 of Section Ill, the use of Section XI acceptance standards has proven to be effective for the inservice inspection (ISi) of piping welds. The NRC staff finds that the use of the ASME Code,Section XI, acceptance standards is appropriate for the proposed alternative, as the alternative is for the repair/replacement activities, and not for new plant construction. Therefore, the NRC staff concludes that the licensee's proposed encoded PAUT for the repair/replacement weld inspection is acceptable because it provides reasonable assurance that any structurally-significant fabrication defects in repaired/replaced welds be detected.
4.0 CONCLUSION
As set forth above, the NRC staff determines that the licensee's proposed alternative provides an acceptable level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all the regulatory requirements set forth in 10 CFR 50.55a(z)(1 ). Therefore, the NRC staff authorizes the use of the proposed alternative in N1-15-CMP-001 for the remainder of the fifth 10-year ISi interval at North Anna, Unit 1, and N2-15-CMP-001 for the fifth 10-year ISi interval and the remainder of the fourth interval at North Anna, Unit 2.
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 Contributor: Ali Rezai, NRR Date: May 28, 2019
ML19140A288 *via email OFFICE DORL/LPLI 1-1 /PM DORL/LPLll-1/LA DMLR/MPHB/(A)BC*
NAME JRHall KGoldstein SCumblidge DATE 05/24/19 05/24/19 05/15/19 OFFICE DORL/LP LI 1-1 /BC DORL/LPLI 1-1 /PM NAME MMarklev JRHall DATE 05/28/19 05/28/19