ML18285A029

Relief Request 59 for the Deferral of Reactor Vessel Beltline Region Interior Attachment Examinations

ML18285A029
Person / Time
Site:	Palo Verde
Issue date:	10/19/2018
From:	Robert Pascarelli Plant Licensing Branch IV
To:	Bement R Arizona Public Service Co
Orenak M, 415-3229
References
EPID L-2017-LLR-0024
Download: ML18285A029 (10)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 19, 2018 Mr. Robert S. Bement Executive Vice President Nuclear/

Chief Nuclear Officer Arizona Public Service Company P.O. Box 52034, Mail Station 7602 Phoenix, AZ 85072-2034

SUBJECT:

PALO VERDE NUCLEAR GENERATING STATION, UNIT 2- RELIEF REQUEST 59 FOR THE DEFERRAL OF REACTOR VESSEL-BEL TUNE REGION INTERIOR ATTACHMENT EXAMINATIONS (EPID L-2018-LLR-0024)

Dear Mr. Bement:

By letter dated March 9, 2018, Arizona Public Service Company (the licensee) submitted Relief Request 59 to the U.S. Nuclear Regulatory Commission (NRC). The licensee proposed an alternative to defer inservice visual examinations for the reactor pressure vessel (RPV) interior attachments within the beltline region at Palo Verde Nuclear Generating Station, Unit 2, from the third 10-year inservice inspection interval program until 2027, plus or minus one refueling cycle.

Specifically, the licensee requested Relief Request 59 in order to allow the subject examinations to occur in conjunction with the deferred inservice examinations of the shell welds, head welds, nozzle welds, RPV interior attachments beyond the beltline, and core support structure components (previously approved in Relief Requests 40 and 44 ), while the fuel and core barrel are removed from the RPV.

Pursuant to Title 10 of the Code of Federal Regulations ( 10 CFR) Section 50.55a(z)(2), the licensee requested the proposed alternative because complying with the current American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

The NRC staff reviewed the licensee's submittal and determined that deferral of the visual examinations would not significantly increase the likelihood of undetected degradation that results in the loss of weld integrity; therefore, the NRC staff finds that performing the examinations as scheduled would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Accordingly, the NRC staff 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(z)(2).

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

R. Bement If you have any questions, please contact the Project Manager, Michael D. Orenak, at 301-415-3229 or via e-mail at Michael.Orenak@nrc.gov.

Sincerely, Robert J. Pascarelli, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. STN 50-529

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 59 REGARDING THE DEFERRAL OF REACTOR VESSEL BEL TUNE REGION INTERIOR ATIACHMENT EXAMINATIONS FOR THE THIRD 10-YEAR INSERVICE INSPECTION INTERVAL ARIZONA PUBLIC SERVICE COMPANY PALO VERDE NUCLEAR GENERATING STATION, UNIT 2 DOCKET NO. 50-529

1.0 INTRODUCTION

By letter dated March 9, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18068A660), Arizona Public Service Company (the licensee) submitted Relief Request (RR) 59, to the U.S. Nuclear Regulatory Commission (NRC). The licensee proposed an alternative to defer inservice visual examinations for the reactor pressure vessel (RPV) interior attachments within the beltline region at Palo Verde Nuclear Generating Station (Palo Verde), Unit 2, from the third 10-year inservice inspection (ISi) interval program until 2027, plus or minus one refueling cycle.

Specifically, the licensee requested Relief Request 59 in order to allow the subject examinations to occur in conjunction with the deferred inservice examinations of the shell welds, head welds, nozzle welds, RPV interior attachments beyond the beltline, and core support structure components (previously approved in Relief Requests 40 and 44), while the fuel and core barrel are removed from the RPV.

Pursuant to Title 10 of the Code of Federal Regulations ( 10 CFR) Section 50.55a(z)(2), the licensee requested the proposed alternative because complying with the current American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

2.0 REGULATORY EVALUATION

Pursuant to 10 CFR 50.55a(g)(4), "lnservice inspection standards requirement for operating plants," the ISi of ASME Code Class 1, 2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination Enclosure

requirements, set forth in the ASME Code,Section XI, to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year ISi interval, and subsequent intervals, comply with the latest edition and addenda of Section XI of the ASME Code that was incorporated by reference in 10 CFR 50.55a(a)( 1)(ii), 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein.

The regulation in 10 CFR 50.55a(z), "Alternatives to codes and standards requirements," states that alternatives to the requirements of 10 CFR 50.55a(g) may be used when authorized by the NRC. A licensee's proposed alternative must be submitted to and authorized by the NRC prior to implementation. The 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 this section would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety...

Based on the above regulatory requirements, and subject to the following technical evaluation, the NRC staff finds that regulatory authority exists for the licensee to propose and the Commission to authorize this alternative to the requirements of the ASME Code,Section XI.

3.0 TECHNICAL EVALUATION

3.1 Licensee's Proposed Alternative

Applicable Code Edition and Addenda

The current Code of record for the Palo Verde, Unit 2, third 10-year ISi interval program is the 2001 Edition and 2003 Addenda of the ASME Code,Section XI.

Components Affected by the Proposed Alternative The proposed alternative is applicable to the ASME Code Class 1 RPV interior attachments within the beltline region at Palo Verde, Unit 2. These attachments are Examination Category B-N-2, Item No. 813.50 components, as shown in Table IWB-2500-1 of the ASME Code,Section XI.

Table 1 of RR 59 in the licensee's submittal, provides the plant-specific weld numbers and locations for each of the Item No. 813.50 attachments {the subject components) addressed in RR59:

• Surveillance Capsule Holder Assemblies at 38 degrees (Azimuth Location within RPV Interior) o 4 Support Bracket Welds (Weld No. 103 -171) o 14GussetWelds(Weld. No.107-171)

• Surveillance Capsule Holder Assemblies at 43 degrees o 4 Support Bracket Welds (Weld No. 103 -171) o 14 Gusset Welds (Weld. No. 107-171)

• Surveillance Capsule Holder Assemblies at 137 degrees o 4 Support Bracket Welds (Weld No. 103 -171) o 14 Gusset Welds (Weld. No. 107-171)

• Surveillance Capsule Holder Assemblies at 142 degrees o 4 Support Bracket Welds (Weld No. 103-171) o 14 Gusset Welds (Weld. No. 107-171)

• Surveillance Capsule Holder Assemblies at 230 degrees o 4 Support Bracket Welds (Weld No. 103-171) o 14 Gusset Welds (Weld. No. 107-171)

• Surveillance Capsule Holder Assemblies at 310 degrees o 4 Support Bracket Welds (Weld No. 103-171) o 14 Gusset Welds (Weld. No. 107-171)

Total Number of Interior Attachment Welds Addressed in RR 59 = 108 Applicable ASME Code Requirements The ASME Code,Section XI, Table IWB-2500-1, Examination Category B-N-2, Item No. B13.50, requires visual examination using the VT-1 examination method 1 (hereafter referred to as VT-1 examinations) of accessible welds for RPV interior attachments within the beltline region every 10-year ISi interval, per the inspection program defined in paragraph IWB-2410.

The Palo Verde, Unit 2, third 10-Year ISi interval began on March 18, 2007, and is scheduled to end on October 31, 2018. The third ISi interval end date of October 31, 2018, includes the 1-year interval extension permitted under paragraph IWA-2430 and an additional ?-month and 14-day interval extension based on NRC authorization of the alternative in RR 56. The NRC staff's previous authorization of RR 56 is addressed in Section 3.2 of this safety evaluation (SE).

Licensee's Proposed Alternative and Reason for Request Pursuant to 10 CFR 50.55a(z)(2), the licensee requested authorization to defer the VT-1 examinations of the subject RPV beltline interior attachments until 2027 plus or minus one refueling cycle.

The licensee stated that its proposed alternative would allow the subject exams to be performed in conjunction with deferred inservice examinations for the Palo Verde, Unit 2, Examination Category B-A RPV shell and head welds, Examination Category B-D RPV nozzle welds, Examination Category B-N-2, Item No. B13.60 RPV interior attachments beyond the beltline region, and Examination Category B-N-3 removable core support structure (CSS) components.

The licensee cited previous NRC-authorized Code alternatives in RR 40 (ADAMS Accession No. ML100290415) and RR 44 (ADAMS Accession No. ML102160487) that allow the deferral of 1 The three visual examination methods (VT-1, VT-2, or VT-3 examinations) are defined in paragraph IWA-2210 of the ASME Code,Section XI.

these third 10-year ISi interval exams until 2027 plus or minus one refueling cycle. The NRC staff's previous authorization of these alternatives is addressed in Section 3.2 of this SE.

Licensee's Basis for Use of the Proposed Alternative The licensee's proposed ISi interval extension for the subject RPV interior attachments within the beltline region was requested on the basis that performing these VT-1 examinations at a time separate from the examinations of the RPV shell welds, head welds, nozzle welds, interior attachments beyond the beltline region, and removable CSS components would result in hardship or unusual difficulty without a compensating increase in quality and safety. The extended inspection interval proposed in RR 59 would align the VT-1 examinations for the subject RPV beltline interior attachments with the other deferred exams that the NRC staff authorized for RR 40 and RR 44, such that all of these examinations are deferred until 2027 plus or minus one refueling cycle.

The licensee stated that the core support barrel and all the fuel must be removed to facilitate the Examination Category B-N-2 (Code Items Nos. 813.50 and 813.60) and the Category B-N-3 (Item No. 813.70) visual examinations of RPV interior components. These visual examinations include VT-1 examinations for Item No. 813.50 RPV interior attachments within the beltline region and VT-3 examinations for Item No. 813.60 RPV interior attachments outside of the beltline region and Item No. 813.70 CSS components. The licensee noted that it has historically performed all Category B-N-2 and B-N-3 visual examinations (VT-1 and VT-3) examinations) during the same outage as the Category 8-A and 8-D volumetric RPV weld examinations. Performing all volumetric and visual examinations required under Categories 8-A, 8-D, B-N-2, and B-N-3 during the same refueling outage will result in a significant reduction in radiation exposure since the RPV internals will only be removed once to accommodate all examinations.

The licensee identified that an unnecessary risk is created by the added removal of the core support barrel to perform VT-1 examinations just for the Item No. 813.50 RPV beltline interior attachments without a compensating increase in quality or safety. The radiation exposure to establish the conditions for and perform the Category B-N-2 and B-N-3 examinations would essentially double if the Item No. B 13.50 examinations were performed at a different time than the other examinations.

The licensee reported that the subject Palo Verde, Unit 1, RPV beltline interior attachments were last examined in spring 2008. The licensee reported no relevant indications from these examinations, nor from the preceding ISi interval exams in 1997. The licensee identified that the Item No. 813.50 interior attachments at Palo Verde, Unit 2, are the surveillance capsule holder assembly attachment welds; each surveillance capsule holder is attached to the RPV cladding by the end brackets (support brackets) and the intermediate brackets (gussets). The licensee reported that these attachments are "lnconel 600" weld material, and they are not major load bearing components. The licensee provided the design stresses and ASME Code-allowable stresses in Table 1 of RR 59 in the licensee's submittal, showing that the design stresses are a fraction of the allowable stresses.

The licensee concluded that deferring the VT-1 examinations of the RPV interior attachments within the beltline region, as proposed in RR 59, reduces the frequency that the RPV lower internals need to be removed and reduces personnel radiation exposure. Therefore, the licensee proposed the 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.

3.2 NRC Staff Evaluation NRC Authorization of RR 56, Third ISi Interval Extension to October 31, 2018 The Palo Verde, Unit 2, third 10-year ISi interval began on March 18, 2007, and was scheduled to end on March 17, 2018, based on the licensee's implementation of the 1-year interval extension allowed by paragraph IWA-2430. The maximum 1-year interval extension per IWA-2430 was implemented without NRC authorization.

By letter dated November 10, 2017 (ADAMS Accession No. ML17318A472), the licensee submitted RR 56 pursuant to 10 CFR 50.55a(z}(1), wherein it requested NRC authorization to extend the ISi interval at Palo Verde, Unit 2, from March 17, 2018, until October 31, 2018; this is 7 months and 14 days beyond the 1-year extension allowed by paragraph IWA-2430. This alternative was applicable to all ASME Code Class 1, 2, and 3 components at Palo Verde, Unit 2. It was submitted to permit better coordination of the ISi programs for the three Palo Verde units on the basis that the interval extension would provide an acceptable level of quality and safety. By letter March 9, 2018 (ADAMS Accession No. ML18067A073), the NRC staff authorized the alternative described in RR 56, and the Palo Verde, Unit 2, third ISi interval was extended until October 31, 2018. Therefore, the VT-1 examinations for Item No. B13.50 RPV beltline interior attachments listed above would need to be performed no later than October 31, 2018, in order to meet the current schedule requirements for the third ISi interval.

Relief Request 59 proposes to further extend the third ISi interval for the subject RPV beltline interior attachment exams until 2027 plus or minus one refueling cycle. This submittal coincided with the NRC's authorization of RR 56 to extend the interval for all ASME Code components until October 31, 2018. As such, the NRC staff determined that the proposed alternative in RR 59 is eligible for evaluation in accordance with the requirements 10 CFR 50.55a(z)(2).

Evaluation of Hardship By letter dated February 22, 2010 (ADAMS Accession No. ML100290415), the NRC staff authorized the licensee's alternative in RR 40 (ADAMS Accession Nos. ML091870432 and ML100040067), pursuant to 10 CFR 50.55a(a}(3)(i)-now 10 CFR 50.55a(z}(1}. Relief Request 40 allows the deferral of RPV volumetric examinations at Palo Verde, Unit 2, until 2027 plus or minus one refueling outage for the following items:

• Examination Category B-A, Item No. B1 .11, RPV Circumferential Shell Weld

• Examination Category B-A, Item No. B1 .12, RPV Longitudinal Shell Welds

• Examination Category B-A, Item No. B1 .22, RPV Meridional Head Weld (Bottom Head Only)

• Examination Category B-A, Item No. B1 .30, RPV Shell-to-Flange Weld

• Examination Category B-D, Item No. B3.90, Nozzle-to-Vessel Welds

• Examination Category B-D, Item No. B3.100, Nozzle Inner Radius Areas The basis for the NRC staff's authorization of RR 40 was that the deferral provided an acceptable level of quality and safety considering the negligible increase in risk associated with the 1O-to-20 year ISi interval extension for the subject RPV pressure-retaining weld exams.

Specifically, the NRC staff's evaluation determined that the licensee demonstrated that the Palo Verde RPVs are bounded by the generic risk-informed RPV integrity analyses supporting these ISi interval extensions in WCAP-16168-NP-A, Revision 2, "Risk-Informed Extension of Reactor Vessel In-Service Inspection Interval" (ADAMS Accession No. ML082820046).

By letter dated August 27, 2010 (ADAMS Accession No. ML102160487), the NRC staff authorized the licensee's alternative in RR 44 (ADAMS Accession Nos. ML092810228 and ML101590516), pursuant to 10 CFR 50.55a(a)(3)(ii)-now 10 CFR 50.55a(z)(2). Relief Request 44 allows the deferral of VT-3 examinations at Palo Verde, Unit 2, until 2027 plus or minus one refueling outage for the following items:

• Examination Category B-N-2, Item No. 813.60, RPV Interior Attachments Beyond the Beltline Region

• Examination Category B-N-3, Item No. 813.70, Removable CSS Components The basis for the NRC staff's authorization of RR 44 was hardship without a compensating increase in quality and safety considering that performing a full core off-load and core support barrel removal is not justified by the added safety associated with meeting the ASME Code requirement (in effect at that time) for completion of these third interval visual exams by March 17, 2018. The NRC staffs authorization of RR 44 pursuant to 10 CFR 50.55a(a)(3)(ii)-

now 10 CFR 50.55a(z)(2) relied on its authorization of RR 40 pursuant to 10 CFR 50.55a(a)(3)(i)-now 10 CFR 50.55a(z)(1). Specifically, the deferred VT-3 examinations for the non-beltline interior attachments and CSS per RR 44 is aligned with the deferred RPV weld volumetric exams per RR 40, such that all exams are performed during the same refueling outage. The NRC determined in its evaluation for RR 44 that deferral of the subject VT-3 examinations provides a reduction in personnel radiation exposure and plant risk because the fuel and core support barrel are removed only once to accommodate both sets of examinations.

For the proposed alternative in RR 59, the NRC staff finds that performance of the Item No. 813.50 RPV beltline interior attachment examinations at a time separate from the other deferred examinations (as authorized for RR 40 and RR 44) would result in the exact same hardship that supports the authorization of RR 44. Specifically, the core support barrel and all the fuel must be removed in order to obtain to access to perform VT-1 examinations of these attachment welds. Therefore, meeting the current ISi interval requirement would result in the licensee having to perform an additional full core off-load, core support barrel removal, and core barrel reinstallation just to perform these Item No. B 13.50 interior attachment examinations by October 31, 2018. Additional core support barrel movement activities create the added risk of causing damage to safety-related structures and components. To remove and reinstall the core support barrel requires implementation of detailed planning and precision lifts to ensure that the RPV and CSS components are not damaged. Core support barrel movements also cause additional radiation exposure to plant personnel because the core barrel itself is highly radioactive. Consistent with the basis for authorizing RR 44, the NRC staff finds that personnel radiation exposure would essentially double if the subject VT-1 examinations were performed at a different time than the deferred examinations of the RPV welds, RPV non-beltline interior attachments, and CSS components 2 .

2 Among other things, the NRC staff considers whether performance of the subject exams to meet the current ISi interval requirement is appropriate given the requirement of 10 CFR Part 20, Section 20.1101 (b ), which specifies that

Meeting the Code Requirement Provides No Compensating Increase in Quality and Safety Considering the hardship associated with performing the Item No. B13.50 interior attachment examinations to meet the current ISi interval requirement, the added quality and safety associated with meeting this specific exam schedule requirement is not sufficient. The licensee reported that no relevant indications for the subject interior attachment welds were found during the previous ISi interval examinations. From a structural standpoint, these welded attachments do not perform a core support function and their design stresses are less than one-half of the stresses allowed by the design requirements, as reported in the licensee's submittal. While these attachments are located in the RPV beltline region, the lack of relevant indications for these items shows that there are no preexisting flaws that would compromise the integrity of these attachments. Further, the lnconel 600 attachment welds are not prone to the same irradiation embrittlement mechanisms as RPV low alloy steel pressure boundary materials and they would not undergo a significant loss of fracture toughness. While some lnconel 600 welds under high operating stress are prone to primary water stress corrosion cracking (PWSCC), the potential for PWSCC is mitigated in this case by the fact that operating stresses for these attachment welds are relatively low and active PWSCC has not yet been observed in the pressurized-water reactor fleet for these types of interior attachments. Therefore, the formation of new flaws that could challenge the structural integrity of these attachments prior to their deferred examination is unlikely. Considering the weld material properties and structural data, the NRC staff finds that there is little concern that deferral of the subject exams until 2027 plus or minus one refueling cycle would significantly increase the likelihood of undetected degradation that results in the loss of weld integrity.

Based on the above evaluation, the NRC staff finds that meeting the current ISi interval requirement to complete the subject Item No. B13.50 interior attachment examinations by October 31, 2018, would result in hardship or unusual difficulty without a compensating increase in the level* of quality and safety.

4.0 CONCLUSION

As set forth above, the NRC staff has determined that compliance with the requirement to perform, no later than October 31, 2018, VT-1 examinations of the subject RPV beltline interior attachments would result in hardship or unusual difficulty for the licensee without a compensating increase in the level of quality and safety. Accordingly, the NRC staff concludes that the licensee has addressed the regulatory requirements set forth in 10 CFR 50.55a(z}(2).

Therefore, the NRC staff authorizes the proposed alternative described in RR 59 for Palo Verde, Unit 2.

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

Principal Contributor: C. Sydnor, NRR Da~:october 19, 2018 licensees shall use, to the extent practical, procedures and engineering controls to achieve occupational doses and doses to members of the public that are "as low as is reasonably achievable (ALARA)."

ML18285A029 *SE via email OFFICE NRR/DORL/LPL4/PM NRR/DORL/LPL4/LA NRR/DMLR/MPHB/BC* NRR/DORL/LPL4/BC NAME MOrenak (MO'Banion for) PBlechman DAIiey RPascarelli DATE 10/17/18 10/17/18 10/1/18 10/19/18