ML18019A195

Proposed Alternative for the Use of Encoded Phased Array Ultrasonic Examination (CAC Nos. MF9923, MF9924, MF9925, MF9926, MF9927, and MF9928; EPID L-2017-LLR-0060)

ML18019A195
Person / Time
Site:	Millstone, Surry, North Anna
Issue date:	01/24/2018
From:	Markley M Plant Licensing Branch 1
To:	Stoddard D Dominion Nuclear Connecticut
HALL J, NRR/DORL/LPLI
References
CAC MF9923, CAC MF9924, CAC MF9925, CAC MF9926, CAC MF9927, CAC MF9928, EPID L-2017-LLR-0060
Download: ML18019A195 (8)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 January 24, 2018 Mr. Daniel G. Stoddard Senior Vice President and Chief Nuclear Officer Innsbrook Technical Center 5000 Dominion Blvd.

Glen Allen, VA 23060-6711

SUBJECT:

MILLSTONE POWER STATION, UNITS 2 AND 3; NORTH ANNA POWER STATION, UNITS 1 AND 2; AND SURRY POWER STATION, UNITS 1 AND 2; PROPOSED ALTERNATIVE FOR THE USE OF ENCODED PHASED ARRAY ULTRASONIC EXAMINATION (CAC NOS. MF9923, MF9924, MF9925, MF9926, MF9927, AND MF9928; EPID L-2017-LLR-0060)

Dear Mr. Stoddard:

By letter dated June 29, 2017 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML17188A379), Dominion Nuclear Connecticut, Inc., and Virginia Electric and Power Company (Dominion or the licensee), submitted alternative request, "Proposed Alternative for the Use of Encoded Phased Array Ultrasonic Examination Techniques In Lieu of Radiography," to request relief from the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code)Section XI, Paragraphs IWA-4221 and IWA-4540(a)(2). ASME Code Section XI, Paragraphs IWA-4221 and IWA-4540(a)(2), require the use of several ASME Code Section Ill subarticles applicable to repaired and replaced components, which in turn specify the use of radiographic examinations. The licensee proposed the use of Phased Array Ultrasonic Testing as an alternative to the required radiographic testing. Specifically, pursuant to Title 10 of the Code of Federal Regulations (1 O 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.

The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed Dominion's request for alternative. As discussed in the enclosed safety evaluation (SE), the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a{z)(1 ). Therefore, the NRC staff authorizes relief request, "Proposed Alternative for the Use of Encoded Phased Array Ultrasonic Examination Techniques In Lieu of Radiography," for the six nuclear power facilities listed in Table 1 of the SE, for the remainder of the 10-year inservice inspection interval for each facility, as specified in Table 1.

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

D. Stoddard If you have any questions on this matter, please contact Randy Hall, Senior Project Manager, at (301) 415-4032 or Randy.Hall@nrc.gov.

Sincerely, Michael T. Markley, Branch Chief Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos.: 50-336, 50-423, 50-338, 50-339, 50-280, 50-281

Enclosure:

Safety Evaluation cc: Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOR THE PROPOSED ALTERNATIVE FOR THE USE OF ENCODED PHASED ARRAY ULTRASONIC EXAMINATION TECHNIQUES IN LIEU OF RADIOGRAPHY DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION, UNITS 2 AND 3 DOCKET NOS. 50-336 AND 50-423 VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-338 AND 50-339 SURRY POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-280 AND 50-281

1.0 INTRODUCTION

By letter dated June 29, 2017 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML17188A379), Dominion Nuclear Connecticut, Inc., and Virginia Electric and Power Company (Dominion, or, the licensee), submitted alternative request "Proposed Alternative for the Use of Encoded Phased Array Ultrasonic Examination Techniques In Lieu of Radiography," to request relief from the requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code)Section XI, Paragraphs IWA-4221 and IWA-4540(a)(2). ASME Code Section XI, Paragraphs IWA-4221 and IWA-4540(a)(2), require the use of several ASME Code Section Ill subarticles applicable to repaired and replaced components, which in turn specify the use of radiographic examinations. The licensee is proposing to use Phased Array Ultrasonic Testing (PAUT) as an alternative to the required radiographic testing.

Specifically, pursuant to Title 1O of the Code of Federal Regulations (1 O 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

The relief request, "Proposed Alternative for the Use of Encoded Phased Array Ultrasonic Examination Techniques in Lieu of Radiography," was submitted in accordance Enclosure

with 10 CFR 0.55a(a)(z)(1 ), which covers requests for alternatives on the basis that the proposed alternative would provide an acceptable level of quality and safety.

The licensee has requested relief from the requirements of ASME Code Section XI, paragraphs IWA-4221 and IWA-4540(a)(2). ASME Code Section XI, section IWA-4200, covers repair/replacement activities, and paragraph IWA-4221 requires that when the licensee replaces an existing item, the replacement shall meet the requirements of the Construction Code to which the original item was constructed.

Paragraph 10 CFR 50.55a(z) states, in part, that alternatives to the requirements of 10 CFR 50.55a(b)-(h) may be used, when authorized by the NRC, if: (1) the proposed alternative would provide an acceptable level of quality and safety; or (2) compliance with the specified requirements 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 for the Commission to authorize the alternative requested by the licensee.

3.0 TECHNICAL EVALUATION

3.1 The Licensee's Relief Request ASME Code Components Affected The licensee's request covers ASME Code,Section XI, ferritic piping butt welds requiring radiography during repair/replacement activities at the nuclear power reactors listed in Table 1.

ASME Code Requirement The ASME Code Section XI, paragraph IWA-4221, requires the owner to use the requirements of the Construction Code for repair/replacement activities. The examination requirements for ASME Section Ill, circumferential butt welds are contained in the ASME Code, Section Ill, Subarticles NB-5200, NC-5200 and ND-5200. The acceptance standards for radiographic testing (RT) are specified in Subarticles NB-5300, NC-5300 and ND-5300.

ASME Codes of Record The Editions and addenda for each nuclear power reactor covered by this request for alternative are listed in Table 1, along with the dates of the current inservice inspection (ISi) interval for each unit.

Table 1: ASME Code Section XI Applicable Codes of Record Plant Interval Edition Start End North Anna Power Station, Unit 1 Fourth 2004 May 1, 2009 April 30, 2019 North Anna Power Station, Unit 2 Fourth 2004 December 14, 201 O December 13, 2020 Surry Power Station, Unit 1 Fifth 2004 December 14, 2013 October 13, 2023 Surry Power Station, Unit 2 Fifth 2004 May 10, 2014 May 9, 2024 Millstone Power Station, Unit 2 Fourth 2004 April 1, 2010 March 31 , 2020 Millstone Power Station, Unit 3 Third 2004 April 23, 2009 April 22, 2019 Proposed Alternative The licensee is proposing to perform encoded PAUT examination techniques using demonstrated procedures, equipment and personnel in accordance with the process defined in ASME approved Code Case N-831, Ultrasonic Examination in Lieu of Radiography for Welds in Ferritic Pipe, dated October 26, 2016.

The encoded PAUT procedures, equipment, and personnel will be qualified using performance demonstration testing. The flaw acceptance standards for the PAUT tests will consider all flaws to be planar and to be evaluated against the preservice acceptance standards of ASME Section XI, IWB-3400, IWC-3400, or IWD-3400 for ASME Code Class 1, 2, or 3 welds, respectively.

Basis for Use The basis for the licensee's request for alternative is that encoded PAUT is equivalent to or superior for detecting and sizing planar flaws as compared to the required radiographic examination. The basis for the proposed alternative was developed from numerous codes, code cases, associated industry experience, articles, and the results of RT and encoded PAUT examinations. The examination procedures and personnel performing examinations are qualified via performance demonstration testing 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.

Ultrasonic testing techniques are being used throughout the nuclear industry for examination of dissimilar metal welds and overlaid welds, as well as other applications, including ASME B31.1 piping replacements.

Duration of Proposed Alternative The licensee is requesting that this proposed alternative be applied for the duration of the current ten-year ISi interval for each of the facilities as described in Table 1.

3.2 NRC Staff Evaluation The licensee is proposing to use encoded PAUT in lieu of radiographic testing for repair and replacement activities in six nuclear power reactors for the remainder of their current 10-year inspection intervals. Ultrasonic testing (UT), like radiographic testing, is a volumetric inspection technique that is commonly used to inspect welds in nuclear power plants and in other industries. Ultrasonic examinations are not equivalent to radiographic examinations as they use different physical mechanisms to detect and characterize discontinuities. These differences in physical mechanisms result in several key differences in sensitivity and discrimination capability.

The NRC staff has been assessing the effectiveness of the use of ultrasound in lieu of radiography since 2009, including literature reviews, detailed evaluations of previous relief requests and proposed alternatives, and confirmatory experimental work to validate the findings.

An assessment of the use of UT in lieu of RT by the NRC is described in the 2015 document NUREG/CR-7204, "Applying Ultrasonic Testing In Lieu of Radiography for Volumetric Examination of Carbon Steel Piping" (ADAMS Accession No. ML15253A674). This report included evaluation of the use of UT in lieu of RT for welded pipes and plates with thicknesses ranging from 0.844 inches to 2.2 inches.

In NUREG/CR-7204, the NRC staff stated that:

Considering overall detections/non-detections for the piping specimens, as well as the Navy plates, it appears that [phased array ultrasonic inspection] PA-UT, based on the techniques applied in this study, provides an equally effective examination for identifying the presence of fabrication flaws in carbon steel welds. The PA-UT parameters applied were shown to be more effective for planar flaws, but slightly less effective for small volumetric flaws, than RT.

Based on this research, the NRC staff finds that there is a sufficient technical basis for the use of UT in lieu of RT for ferritic steel welds. Given that UT in lieu of RT can be effective, the NRC staff considered whether the proposed alternative applies UT in a way that provides reasonable assurance of finding structurally-significant flaws.

Important aspects of this proposed alternative include:

The examination volume shall include 100 percent of the weld volume and the weld-to-base metal interface.

The electronic data files for the PAUT examinations will be stored as archival-quality records. In addition, hard copy prints of the data will be included as part of the PAUT examination records to allow viewing without the use of hardware or software.

Ultrasonic examination procedures shall be qualified by using either a blind or a non-blind performance demonstration using a minimum of 30 flaws covering a range of sizes, positions, orientations, and types of fabrication flaws. The demonstration set shall

include specimens to represent the minimum and maximum diameter and thickness covered by the procedure.

The flaw through-wall heights for the performance demonstration testing shall be based on the applicable acceptance standards for volumetric examination in accordance with IWB-3400, IWC-3400 or IWD-3400. At least 30 percent of the flaws shall be classified as acceptable planar flaws, with the smallest flaws being at least 50 percent of the maximum allowable size based on the applicable a/I aspect ratio for the flaw.

Ultrasonic examination personnel shall demonstrate their capability to detect and size flaws by performance demonstration using the qualified procedure. The demonstration specimen set shall contain at least 1O flaws covering a range of sizes, positions, orientations, and types of fabrication flaws.

All flaws detected using angle-beam ultrasonic inspections will be treated as planar flaws and will be evaluated against the preservice acceptance standards of ASME Section XI, IWB-3400, IWC-3400, or IWD-3400 for ASME Code Class 1, 2, or 3 welds, respectively.

Based on the inspection and qualification requirements described in the licensee's request for alternative and the evaluation results reported in NUREG/CR-7204, the NRG staff concludes that there is reasonable assurance that the encoded phased array UT, applied and qualified as proposed by the licensee, will provide an adequate level of quality and safety.

4.0 CONCLUSION

As set forth above, the NRG staff concludes that the licensee's proposed alternative to use ultrasonic testing in lieu of radiographic testing using encoded phased array examinations provides reasonable assurance of structural integrity and leak tightness of Class 1 and 2 ferritic piping welds. Thus, ultrasonic testing using the procedure described in the submittals of the subject welds would provide an adequate level of quality and safety. Accordingly, the NRG staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(z)(1 ). Therefore, the NRG staff authorizes relief request, "Proposed Alternative for the Use of Encoded Phased Array Ultrasonic Examination Techniques In Lieu of Radiography," for the six nuclear power reactors described in Table 1 for the remainder of the 10-year inservice inspection interval for each unit, as listed in Table 1.

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

Principal Contributor: S. Cumblidge Da~: January 24, 2018

ML18019A195 *via email OFFICE LPLll-1/PM LPLll-1/LA DMLR/MPHB/BC* LPLll-1/BC LPLll-1/PM NAME JRHall KGoldstein DAIiey MMarkley JRHall DATE 01/23/2018 01/23/2018 12/18/2017 01/24/2018 01/24/2018