ML14282A479

Relief Request ANO1-ISI-023, Volumetric Examination Frequency Requirements, for the Fourth 10-Year Inservice Inspection Interval

ML14282A479
Person / Time
Site:	Arkansas Nuclear
Issue date:	10/29/2014
From:	Markley M Plant Licensing Branch IV
To:	Entergy Operations
George A
References
TAC MF3176
Download: ML14282A479 (8)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 29, 2014 Vice President, Operations Arkansas Nuclear One Entergy Operations, Inc.

1448 S.R. 333 Russellville, AR 72802

SUBJECT:

ARKANSAS NUCLEAR ONE, UNIT NO. 1 -REQUEST FOR ALTERNATIVE AN01-ISI-023 TO ASME CODE CASE N-770-1 VOLUMETRIC EXAMINATION FREQUENCY REQUIREMENTS FOR THE FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL (TAC NO. MF3176)

Dear Sir or Madam:

By letter dated October 8, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13281A478), Entergy Operations, Inc. (Entergy, the licensee), submitted a request to the U.S. Nuclear Regulatory Commission (NRC) for the use of an alternative to an inspection frequency requirement of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) Case N-770-1, "Alternative Examination Requirements and Acceptance Standards for Class 1 PWR [Pressurized-Water Reactor] Piping and Vessel Nozzle Butt Welds Fabricated with UNS N06082 or UNS W86182 Weld Filler Material with or without Application of Listed Mitigation Activities," associated with inspection of reactor pressure vessel (RPV) core flood dissimilar metal (OM) piping-to-nozzle welds at Arkansas Nuclear One (ANO), Unit 1.

Specifically, pursuant to Title 10 of the Code of Federal Regulations (1 0 CFR) 50.55a(a)(3)(ii),

the licensee requested to use an alternative on the basis that complying with the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

The NRC staff has reviewed the licensee's submittal and concludes, as set forth in the enclosed safety evaluation, that Entergy has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(a)(3)(ii), and is in compliance with the requirements of 10 CFR 50.55a with the authorization of this alternative. Therefore, the NRC staff authorizes the alternative examination frequency for the examinations of the components contained in Request for Alternative AN01-ISI-023 for the ANO, Unit 1, fourth 10-year in service inspection interval.

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.

If you have any questions, please contact the ANO Project Manager, Andrea George, at (301) 415-1081 or by e-mail at Andrea.George@nrc.gov.

Sincerely, Michael T. Markley, Chief Plant Licensing Branch IV-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-313

Enclosure:

Safety Evaluation cc w/encl: Distribution via Listserv

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• • • • ... SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR ALTERNATIVE AN01-ISI-023 ENTERGY OPERATIONS, INC.

ARKANSAS NUCLEAR ONE. UNIT 1 DOCKET NO. 50-313

1.0 INTRODUCTION

By letter dated October 8, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13281A478), Entergy Operations, Inc. (Entergy, the licensee), requested relief from the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) associated with the inspection frequency of reactor pressure vessel (RPV) core flood dissimilar metal (OM) piping-to-nozzle welds at Arkansas Nuclear One (ANO), Unit 1.

Specifically, pursuant to Title 10 of the Code of Federal Regulations (1 0 CFR) 50.55a(a)(3)(ii),

the licensee requested to use the proposed alternative on the basis that complying with the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

2.0 REGULATORY EVALUATION

In its relief request, the licensee proposes to use an alternative to an inspection frequency requirement of ASME Code Case N-770-1, "Alternative Examination Requirements and Acceptance Standards for Class 1 PWR [Pressurized-Water Reactor] Piping and Vessel Nozzle Butt Welds Fabricated with UNS N06082 or UNS W86182 Weld Filler Material with or without Application of Listed Mitigation Activities."

The regulations in 10 CFR 50.55a(g)(6)(ii) state that the Commission may require the licensee to follow an augmented inservice inspection (lSI) program for systems and components for which the Commission deems that added assurance of structural reliability is necessary.

Paragraph 10 CFR 50.55a(g)(6)(ii)(F) requires, in part, an augmented inservice volumetric inspection of Class 1 piping and nozzle OM butt welds of pressurized-water reactors (PWRs) in accordance with ASME Code Case N-770-1, subject to the conditions specified in paragraphs (2) through ( 10) of 10 CFR 50.55a(g)(6)(ii)(F).

Enclosure

Alternatives to requirements under 10 CFR 50.55a(g) may be authorized by the U.S. Nuclear Regulatory Commission (NRC) pursuant to 10 CFR 50.55a(a)(3)(i) or 10 CFR 50.55a(a)(3)(ii).

In proposing alternatives or requests for relief, the licensee must demonstrate that: (1) the proposed alternatives 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 analysis of the regulatory requirements, the NRC staff concludes that the regulatory authority exists to authorize the licensee's proposed alternative on the basis that compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Accordingly, the NRC staff has reviewed and evaluated the licensee's request pursuant to 10 CFR 50.55a(a)(3)(ii).

3.0 TECHNICAL EVALUATION

3.1 Licensee's Relief Request 3.1.1 Component Identification Core Flood Nozzle to Safe End DM Welds01-025 and 01-026 3.1.2 Code Requirements for Which Relief is Requested ASME Code Case N-770-1 requires subsequent volumetric examination of all Inspection Item B welds, as defined in Table 1 of the Code Case, of essentially 100% of each weld once every second inspection period not to exceed 7 years.

The Code of record for the fourth interval is the ASME Code,Section XI, 2001 Edition with 2003 Addenda.

3.1.3 Licensee's Proposed Alternative The licensee proposes a one-time extension to the Code Case N-770-1, Table 1, Inspection Item B, volumetric examinations from a period of 84 months (7 years) to 96 months (8 years).

3.1.4 Licensee's Duration of Relief Request The licensee requests an alternative from the regulatory requirement which would require inspection no later than November 2015 in order to allow the inspection to be performed during the scheduled fall 2016 refueling outage at ANO, Unit 1, no later than November 2016. This is a one-time extension inspection frequency request.

3.1.5 Licensee's Basis for Relief The licensee stated relief was requested due to the need to examine the core flood piping-to-nozzle welds from the inside surface of the weld. This requires access to the lower portion of the reactor vessel to insert automated volumetric inspection equipment to perform the examination. As such, it would be necessary to remove the core barrel and other RPV

internals. ANO, Unit 1 plans to align the N-770-1 core flood weld examinations with the 10-year reactor vessel examination and the Materials Reliability Program (MRP)-227, Pressurized Water Reactor Internals Inspection and Evaluation Guidelines," required reactor vessel internals examination. Aligning these examinations greatly reduces costs and dose that would be required to remove the internals in consecutive outages. The dose received for the removal and replacement of the core barrel alone was approximately 330 millirem (mrem).

The licensee's technical basis for the relief request is based on the previous inspection history at ANO, Unit 1, and the application of weld onlays in the fall 2008.

The licensee stated that the core flood welds that are the subject of this relief request were inspected in November 2008 with Performance Demonstration Initiative (PDI)-qualified volumetric examinations, which found no indications in the weld.

The licensee notes that ANO, Unit 1 entered an extended shutdown during the 2013 refueling outage for approximately 4.5 months. This added shutdown time reduces the service time of the components accordingly.

The licensee also described a modification to isolate the susceptible Alloy 600 material from reactor coolant by installation of a weld onlay. Prior to beginning the weld modification, the weld joints to both core flood nozzles in this relief request were examined to lSI requirements with qualified Appendix VIII ultrasonic examination procedures and personnel and were accepted with no indications noted.

After the acceptable lSI examinations, the core flood piping was drained and the welds were prepared to support the application of the weld onlay. The licensee notes that as part of the preparations, a liquid penetrant examination was preformed to verify no indications of primary water stress-corrosion cracking (PWSCC) or other unacceptable indications in the OM weld or butter region. The on lay weld was applied to an area exceeding 4 inches on each side of the OM weld centerline. After the final onlays for the subject welds were accepted visually and with liquid penetrant examinations, an Electric Power Research Institute (EPRI)-demonstrated volumetric ultrasonic examination was performed and accepted to the requirements of ASME Code, Section Ill for cladding. These examinations were completed on November 27, 2008.

After refilling the core flood piping, the lSI ultrasonic examinations were repeated on the subject welds with the onlays installed as a new baseline examination, with no indications noted.

The purpose of the on lay modification was to verify PWSCC was not present on either of the core flood nozzle OM welds and to subsequently isolate any susceptible material from the primary water environment. The multiple inspections applied to the onlay welding were to provide assurance of the barrier integrity. The licensee notes that it is not requesting NRC acceptance of the onlay as a qualified mitigation in accordance with Code Case N-770-1 as modified by 10 CFR 50.55a(g)(6)(ii)(F)(2); the information is provided as some compensation for any risk associated with extending the inspection interval.

3.2 NRC Staff Evaluation The NRC staff notes that the generic rules for the frequency of volumetric examination of OM butt welds were established to provide reasonable assurance of the structural integrity of the

reactor coolant pressure boundary. As such, the staff notes that plant-specific analysis could be used to provide a basis for inspection relief if the inspection requirement presents a significant hardship. The staff reviewed the licensee's proposed alternative under the requirements of 10 CFR 50.55a(a)(3)(ii), such that "compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety."

As the current core flood nozzle-to-safe end DM weld inspection frequency would require the licensee to remove the RPV internals for these examinations in the fall 2014 refueling outage, in addition to the ASME Code,Section XI, Table IWB-2500-1, 10-year reactor vessel inspection scheduled for ANO, Unit 1 during the fall 2016 refueling outage (1 R26), the NRC staff concludes that the licensee had a sufficient basis for a radiological dose hardship.

The NRC staff also notes that the on lays installed and examined in 2008 provides reasonable assurance that PWSCC was not present in the core flood nozzle DM welds and that any susceptible material is now isolated from the primary water environment. In addition, the onlay material, Alloy 52, is resistant to crack initiation and has a slower crack growth rate than the original Alloy 82/182 weld material. The presence of the onlay, while not a qualified mitigation technique in accordance with Code Case N-770-1, as modified by 10 CFR 50.55a(g)(6)(ii)(F)(2),

does provide an adequate technical basis to allow for the one-time extension of the inspection interval.

Therefore, due to the hardship of the location of the core flood nozzle to safe-end DM welds (and associated radiological dose), the inspection history of the subject welds at ANO, Unit 1, and onlay installation demonstrating a sufficient safety margin, the NRC staff concludes that the licensee has provided adequate technical basis to demonstrate that compliance with the requirements of 10 CFR 50. 55a(g)(6)(ii)(F) for the volumetric inspection of the core flood nozzle to safe-end DM welds at ANO, Unit 1 during the fall 2015 refueling outage would cause an unnecessary hardship or unusual difficulty without a compensating increase in the level of quality and safety, given that the reactor vessel internals will be removed during the fall 2016 (1 R26) refueling outage at ANO, Unit 1.

4.0 CONCLUSION

As set forth above, the NRC staff concludes that the proposed alternative provides reasonable assurance of structural integrity of the subject components and that complying with the requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Accordingly, the NRC staff concludes that the licensee has adequately addressed all of the regulatory requirements set forth in 10 CFR 50.55a(a)(3)(ii).

Therefore, the NRC staff authorizes the use of the proposed alternative to Code Case N-770-1 examination requirements for the one time extension of the inspection interval to the fall 2016 refueling outage (1R26) at ANO, Unit 1, no later than November 2016, at which time, the licensee is expected to be able to meet the examination coverage requirements for these welds.

All other ASME Code,Section XI, requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear lnservice Inspector.

Principal Contributor: M. Audrain, NRR/DE/EPNB Date: October 29, 2014

ML14282A479 *via email OFFICE NRRIDORLILPL4-1/PM NRR/DORLILPL4-1/LA NRRIDE/EPNB/BC NRRIDORLILPL4-1/BC NAME AGeorge JBurkhardt DAiley* MMarkley DATE 10/20/14 10/10/14 10/7/14 10/29/14